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金属学报, 2023, 59(9): 1125-1143 DOI: 10.11900/0412.1961.2023.00223

综述

γ' 相强化钴基高温合金成分设计与蠕变机理研究进展

冯强,1, 路松1, 李文道1,2, 张晓瑞1, 李龙飞,1, 邹敏1, 庄晓黎1

1北京科技大学 新金属材料国家重点实验室 北京材料基因工程高精尖创新中心 北京 100083

2湘潭大学 材料科学与工程学院 湘潭 411105

Recent Progress in Alloy Design and Creep Mechanism of γ'-Strengthened Co-Based Superalloys

FENG Qiang,1, LU Song1, LI Wendao1,2, ZHANG Xiaorui1, LI Longfei,1, ZOU Min1, ZHUANG Xiaoli1

1Beijing Innovation Center for Materials Genome Engineering, State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China

2School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, China

通讯作者: 冯 强，qfeng@skl.ustb.edu.cn，主要从事镍基/钴基铸造高温合金以及热端部件服役损伤评价方面的研究；李龙飞，lilf@skl.ustb.edu.cn，主要从事镍基和新型钴基高温合金方面的研究

责任编辑: 毕淑娟

收稿日期: 2023-05-18   修回日期: 2023-08-10  

基金资助: 国家自然科学基金项目(52171095)
国家自然科学基金项目(52201100)
国家自然科学基金项目(52201024)
国家自然科学基金项目(51771019)
国家自然科学基金项目(92060113)
国家重点研发计划项目(2017YFB0702902)
中国博士后科学基金项目(2022M710346)

Corresponding authors: FENG Qiang, professor, Tel:(010)62333751, E-mail:qfeng@skl.ustb.edu.cn;LI Longfei, associate professor, Tel:(010)62334862, E-mail:lilf@skl.ustb.edu.cn

Received: 2023-05-18   Revised: 2023-08-10  

Fund supported: National Natural Science Foundation of China(52171095)
National Natural Science Foundation of China(52201100)
National Natural Science Foundation of China(52201024)
National Natural Science Foundation of China(51771019)
National Natural Science Foundation of China(92060113)
National Key Research and Development Program of China(2017YFB0702902)
China Postdoctoral Science Foundation(2022M710346)

作者简介 About authors

摘要

近年来，随着航空发动机和地面燃机的持续发展，对其关键热端部件的环境抗力和承温能力的要求越来越高，γ′相强化钴基高温合金在抗热腐蚀性能和熔点温度等方面较镍基高温合金具有优势。为了促进此类合金的发展，本文基于国内外在合金开发和蠕变性能等方面的研究成果，结合本课题组的研究工作，总结了该类合金在合金化原理、合金设计方法和蠕变机理等方面的研究现状，凝练出了目前该类合金发展存在的关键基础科学问题，并对未来需要关注的研究方向进行了概述。

关键词： 钴基高温合金; γ'相强化; 合金化; 合金设计; 蠕变

Abstract

Recently, with the development of aviation engines and ground-based gas turbines, the demands for the environmental resistance and temperature-bearing capacity of their key hot-end components have considerably increased. Compared to Ni-based superalloys, novel γ′-strengthened Co-based superalloys are more advantageous owing to their corrosion resistance and melting temperature. To facilitate the development of these alloys, research on their alloying principles, alloy design, and creep mechanisms is summarized in this paper based on domestic and international results. Furthermore, herein, the key scientific problems in the development of such alloys are discussed, and the possible development trends and challenges in the future are surveyed.

Keywords： Co-based superalloy; γ'-strengthened; alloying; alloy design; creep

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冯强, 路松, 李文道, 张晓瑞, 李龙飞, 邹敏, 庄晓黎. γ' 相强化钴基高温合金成分设计与蠕变机理研究进展[J]. 金属学报, 2023, 59(9): 1125-1143 DOI:10.11900/0412.1961.2023.00223

FENG Qiang, LU Song, LI Wendao, ZHANG Xiaorui, LI Longfei, ZOU Min, ZHUANG Xiaoli. Recent Progress in Alloy Design and Creep Mechanism of γ'-Strengthened Co-Based Superalloys[J]. Acta Metallurgica Sinica, 2023, 59(9): 1125-1143 DOI:10.11900/0412.1961.2023.00223

镍基和钴基高温合金是航空、航天、舰船、能源和化工等领域使用的重要高温结构材料。随着我国制造强国战略的实施，上述领域的核心装备，如先进航空发动机、重型地面燃气轮机和压力反应容器，面临日益严苛的高温、热腐蚀和复杂载荷等服役环境。对比镍基高温合金，碳化物强化传统钴基高温合金的熔点温度更高，且具有优异的耐蚀性、抗热疲劳性、可铸性及焊接性，非常适用于制造航空发动机燃烧室及导向叶片、重型燃气轮机用大尺寸叶片以及大型高温压力反应釜等在极端条件下服役的关键部件，但缺乏γ'相强化机制限制了该类合金的承温能力，严重阻碍了其在更高温度(> 800℃)下的工程应用。2006年，Sato等[1]在Co-Al-W基合金体系中发现了γ'溶解温度达到990℃的γ'-Co3(Al, W)相，比γ'-Co3Ti和Co3Ta提高了250℃左右，预示着γ'相强化新型钴基高温合金体系有望实现高承温能力和高环境抗力的结合。2014年5月，在法国举行的每四年一届的欧洲高温合金大会(EuroSuperalloys 2014)上，主旨报告人将γ'相强化钴基高温合金(以下简称“钴基高温合金”)列为高温合金材料技术(high temperature materials technology trends)未来发展的七大趋势之一。目前，该类合金在合金设计、制备、高温力学性能、氧化性能等方面取得了一系列成果，并制备出了大尺寸的钴基单晶高温合金燃机叶片[2]，表现出了良好的工程应用潜力。

本文结合国内外相关学者的研究成果，基于本课题组多年来在钴基高温合金的合金化原理、成分设计优化和变形机制等方面的工作，系统总结了该类合金的化学成分与组织特征、典型合金体系和蠕变机理方面的研究现状，并对其未来的研发方向进行了概述。

1 钴基高温合金的成分与组织特征

高温合金的成分与组织是其性能的决定因素，揭示成分与组织特征的对应关系是高温合金设计的重要基础。尽管钴基与镍基高温合金具有相似的γ/γ'两相组织，但其化学成分和组织特征(γ/γ'点阵错配度、两相元素配分、二次相析出、γ'相粗化和长大等)存在一定差异。

1.1 化学成分特征与合金元素作用

表1列出了钴基高温合金的主要合金元素。与镍基高温合金类似，可以将其分为γ相形成元素和γ'相形成元素；下面将分别进行阐述。

表1   γ'相强化钴基高温合金的主要合金元素及其作用

Table 1  Typical elements and their effect on the γ'-strengthened Co-based superalloys

TypeElementRadiusDensityPositive effectNegative effect
nmg·cm-3
γ formerCo0.1258.9--
Ni0.1258.9Enlarge γ + γ' regionForm η phase with Ti
Cr0.1287.2Enhance oxidation/corrosionDecrease the stability of γ' phase, form
resistancesecondary phases
Fe0.1267.9Stabilize γ phaseDecrease the stability of γ' phase
γ′ formerAl0.1432.7Stabilize γ' phase, enhanceForm β phase
oxidation resistance
W0.14119.4Stabilize γ' phase,Increase alloy density, form μ and χ phases
enhance creep property
Ti0.1724.5Stabilize γ' phase,Form β and η phases
enhance creep property
Ta0.14716.5Stabilize γ' phase,Form μ and χ phases
enhance creep property
Mo0.14010.2Solution strengtheningForm μ and χ phases
Nb0.1478.5Stabilize γ′ phase,Form μ, χ, and Laves phases
enhance strength
V0.1356.1Stabilize γ′ phase,Decrease oxidation resistance
enhance strength
Hf0.15913.3Stabilize γ′ phase,Form Laves phase
enhance strength

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(1) γ相形成元素

γ相形成元素主要有Co、Ni、Cr、Fe等，主要进入到γ基体中。其中，Ni可以有效扩大γ + γ'两相区，提高组织稳定性[3]，但在高Ti合金体系中会与Ti形成片状析出相η-Ni3Ti[4]；此外，Ni还会促进高W合金体系中χ-D019相的析出[5]，降低力学性能。Cr是提高抗氧化和抗腐蚀性能最有效的合金元素，其在合金表面形成的Cr2O3保护层可以显著降低氧化速率。但是，Cr的添加会严重降低合金γ'相的稳定性，并促进二次相析出[6~8]。Fe可以起到稳定γ基体的作用，但会降低γ'相的稳定性[6,8,9]。因此，一般不添加Fe。

(2) γ'相形成元素

γ'相形成元素主要有Al、W、Ti、Ta、Mo、Nb、V和Hf等，它们在一定程度上提高γ'相的热力学稳定性。其中，以Ti、Ta、Nb的效果最为显著[6,10,11]，每添加1% (在无特殊说明情况下，本文中合金元素含量均为原子分数)的上述元素可分别使γ′相溶解温度提高29、44和27℃。部分γ'相形成元素还能有效提高合金的力学性能，如Ti、Ta、W可以有效提高合金的蠕变性能[9,12~15]，Mo、Nb可以提高合金的屈服强度[16,17]。此外，Al还能在合金基体表面形成致密的保护性Al2O3层，提高合金的高温抗氧化性能。但是，γ'相形成元素的过量添加会不同程度地促进有害二次相析出，如β-B2相等，降低合金的组织稳定性[1,7,8,18]。值得一提的是，在镍基高温合金中，W、Mo、V等一般被认为是γ相形成元素，这与钴基高温合金不同。

1.2 γ/γ' 两相组织稳定性

1.2.1 γ/γ'点阵错配度与两相元素配分行为

(1) 点阵错配度

γ/γ'点阵错配度(δ)是影响高温合金组织稳定性和力学性能的重要参数，其表达式为：δ = 2(aγ' - aγ ) / (aγ' + aγ )(其中，aγ 和aγ' 分别为γ和γ'相的点阵常数)。商用镍基单晶高温合金的δ一般为负值(-0.3%~-0.1%)，这主要与Re、W、Mo等大尺寸原子在γ相中富集有关(使aγ' < aγ )[19]。与镍基高温合金相反，钴基高温合金的δ一般为正值。Sato等[1]报道的Co-9.2Al-9W合金δ为+0.53%，其绝对值高于镍基单晶高温合金的平均水平。Ni、Cr和Mo的添加会降低钴基高温合金δ的绝对值，促进γ'相形貌由立方状向球形转变[3,20,21]，这主要与上述元素诱导的γ/γ'两相元素配分行为改变有关。与此相反，Ti、Ta和W等则提高δ的绝对值[16,22]。Ti、Ta和W等大尺寸原子倾向于进入γ'相，显著提高γ'相晶格常数，但对γ相晶格常数无明显影响。

温度也是δ的影响因素。随着温度的提高，γ和γ'相晶格均会发生膨胀，且γ相晶格热膨胀系数一般高于γ'相。由于镍基和钴基高温合金中aγ 和aγ' 的相对大小不同，温度升高对δ产生的影响也不同。钴基高温合金的aγ' > aγ，温度升高将使δ绝对值减小，如图1a[15]所示；而镍基高温合金的aγ' < aγ，温度升高使δ绝对值增大，如图1b[23]所示。此外，蠕变也会对δ产生影响。Coakley等[24]针对上述2种合金的研究均发现，在蠕变过程中，合金δ绝对值逐渐增大；这可能与界面位错的形成诱导γ/γ'相共格程度降低有关。

图1

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图1   温度对γ′相强化钴基[15]和镍基[23]高温合金错配度的影响

Fig.1   Effects of temperature (T) on lattice misfit (δ) in γ'-strengthened Co-based (a)[15] and Ni-based (b)[23] superalloys (aγ —lattice constant of γ phase, aγ' —lattice constant of γ' phase)


(2) 元素配分行为

在高温合金中，合金元素(X)在γ和γ'相中的配分倾向通常用成分配分比Kγ'/γX表示，其表达式为：Kγ'/γX=Cγ'X / CγX (式中，Cγ'X和CγX分别为X在γ'和γ相中的浓度)。在钴基高温合金中，Co、Mn、Fe、Cr和Re等倾向分布在γ相中；而Ni、Al、W、Mo、V、Nb、Ti、Ta等倾向分布在γ'相中[3,10,25]，如图2[26]所示。镍基高温合金的元素配分行为与钴基高温合金存在一定差异，W、Mo和V等倾向分布在γ相中[19,27]。

图2

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图2   钴基高温合金中γ/γ'两相的成分分布[26]

Fig.2   Elemental partitioning between γ and γ' phases in a γ'-strengthened Co-based superalloy[26] (HAADF—high-angle annular dark field)


通常，合金元素的γ/γ'两相配分行为会一定程度上影响合金的组织稳定性。例如，在Co-Al-W基合金中添加Ni可使Al和W的两相配分行为发生明显变化，从而引起合金δ的降低[3]。再如，添加Cr可使Co-Al-W基合金中W、Ta和Mo等难熔元素向γ相中富集，这会显著增加二次相析出的倾向[7,8,11,18]。此外，钴基高温合金中Kγ'/γX与γ'相溶解温度呈正相关关系，Kγ'/γX < 1的合金元素往往会降低γ'相稳定性[10]。

1.2.2 γ基体稳定性

二次相在γ基体中析出被认为是高温合金组织不稳定的一种重要表现。镍基高温合金中的二次相主要指拓扑密排 (topolog-ically close packed，TCP)相[19]；在钴基高温合金中，主要的二次相有β-B2相、χ-D019相和μ-D85相[1]。其中，μ相属于TCP相。以上二次相均会降低合金的力学性能[19]，因而需要避免析出。

Co-Al-W三元合金体系中γ + γ'两相区较窄，这导致其在合金化的过程中容易析出二次相。Xue等[18]研究表明，在Co-9Al-10W三元合金中，仅添加2%的Ta、Mo、Nb等难熔元素即会导致合金析出大量的μ相；将上述合金元素的含量提高至4%后，合金的μ相析出量增加，并进一步析出χ相。与此同时，二次相的析出导致合金的γ'相含量降低。Yan等[8]通过研究合金元素对Co-7Al-7W三元合金的作用也得到了类似的结论；另外，添加Cr和Fe等γ相形成元素也会促进合金中有害二次相(如β相和χ相)的析出。Shinagawa等[3]研究发现，添加一定量的Ni能有效扩大γ + γ'两相区。因此，钴基高温合金中，一般会加入25%~35%的Ni来扩大γ + γ'两相区，以提高合金化的能力[3,12,28,29]。

1.2.3 γ'相稳定性

(1) γ'相溶解温度

γ'相溶解温度是影响高温合金组织稳定性和力学性能的主要因素之一。目前，镍基高温合金中γ'相溶解温度已经接近其熔点，很难再进一步提升；而钴基高温合金的熔点比镍基高温合金高50~150℃[10,30]，其γ'相溶解温度具有潜在的上升空间。

添加γ'相形成元素是提高γ'相溶解温度的有效手段，而不同合金元素对γ'相溶解温度的影响并不相同。Ti、V、Nb、Ta、Hf、W、Ni、Mo和Zr等均可提高γ'相溶解温度；其中，Ti、Ta和Nb的作用最为显著[10,11]。通过优化上述合金元素含量，可使合金中γ'相溶解温度达到1100℃以上，部分合金已经突破1200℃[6,10,29,31,32]，如表2[1,6,7,10,11,13,21,25,32~42]所示。另一方面，添加Cr、Mn、Fe、Re和Os等则会降低γ'相溶解温度[10,11,43]。因此，除了Cr和Re之外，其他降低γ'相溶解温度的合金元素很少被引入该类合金中。

表2   部分钴基高温合金的名义成分和γ'相溶解温度(Tγ'-solvus) [1,6,7,10,11,13,21,25,32~42]

Table 2  Nominal compositions and γ' solvus temperature (Tγ'-solvus) of some γ'-strengthened Co-based superalloys[1,6,7,10,11,13,21,25,32-42]

Alloy (atomic fraction / %)Tγ'-solvus / oCRef.
Co-9Al-9.8W990[33]
Co-8.8Al-9.8W-2Ta1079[1,33]
Co-7Al-8W-4Ti-1Ta1131[32]
Co-7Al-7W-4Ti-2Ta1157[13]
Co-7Al-6W-4Ti-2Ta-1Mo1143[7]
Co-7Al-6W-4Ti-2Ta-1Nb1150[7]
Co-10Ni-5Al-5W-8Ti1137[34]
Co-20Ni-9Al-6W-4Ta-2Mo1178[21]
Co-30Ni-7Al-7W-4Ti-1Ta1167[25]
Co-30Ni-11Al-4W-4Ti-1Ta1202[35]
Co-30Ni-10.5Al-4Ti-7W-2.5Ta1269[36]
Co-30Ni-11Al-4W-4Ti-1Ta-5Cr1173[37]
Co-30Ni-10Al-5Mo-2Ta-2Ti-10Cr1078[38]
Co-35.4Ni-9.9Al-4.9Mo-2.8Ta-3.5Ti-5.9Cr1156[39]
Co-32Ni-9Al-2W-1Ti-1Ta-14Cr-2.5Mo-0.5Nb1050[40]
Co-32Ni-11Al-2W-2Ti-3Ta-5Cr-0.5Mo-0.5Nb1201[41]
Ni-based wrought superalloy928-1159[6,10,11]
Ni-based single crystal superalloy1221-1330[6,10,11,42]

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(2) γ'相粗化和长大

高温合金力学性能与γ'相尺寸相关，通常具有一个最佳尺寸，使其力学性能达到最高[19]。然而，随着服役时间的延长，γ'相将发生粗化和长大，导致合金的高温力学性能降低。因此，为了保持良好的高温力学性能，需要控制γ'相的粗化长大。

Co-Al-W三元合金中γ'相粗化符合Lifshitz-Slyozov-Wagner (LSW)扩散控制机制，扩散速率较慢的W是其粗化行为的主要控制元素[44]。Ni的添加会使γ'相粗化控制元素发生改变。例如，在Co-7Al-7W合金中添加20%Ni会使γ'相中Al含量增加，W含量降低，粗化控制元素由W转变为Al。Al在γ基体中的扩散系数明显大于W，使合金γʹ相粗化速率增加，从而导致γ'相尺寸明显增大[45]。在Co-Al-W-Ti-Ta合金体系中，Mo的添加能够降低γ'相的粗化速率，这主要与Mo降低γ/γ'两相界面能有关[46]。

对比镍基高温合金，钴基高温合金中γ'相具有更低的粗化速率。这主要与合金元素在Co中的较低扩散系数有关(图3[47])，为其长时组织稳定性奠定了理论基础。

图3

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图3   部分合金元素在Co和Ni中的扩散系数[47]

Fig.3   Mean diffusion coefficients (D¯) of some alloying elements of fourth (a) and fifth (b) period in Co and Ni[47]


2 钴基高温合金的研发现状和发展趋势

2.1 合金体系的发展现状和趋势

2.1.1 Co-Al-W合金体系

1971年，Lee[48]在其博士论文中报道了一种含稳定γ'相的Co-10.0Al-9.1W三元合金，但在当时并未得到重视。2006年，Sato等[1]在研究Co-Al-W三元系相图时再次发现了高温稳定的γ'-Co3(Al, W)相，其稳定存在温度高达990℃，较先前研究的γ'-Co3Ti和Co3Ta提高了近250℃。另外，Co-9.2Al-9W三元合金在900℃的屈服强度和塑性与商用镍基高温合金Waspaloy相当。然而，Co-Al-W基合金的发展初期仍面临诸多挑战，如γ + γ'两相区较窄、组织稳定性较差、γ′相溶解温度较低、高温抗氧化性能较差、合金密度较高等。因此，早期的研究[3,6,8,11,18]多围绕Co-Al-W基合金的合金化原理展开，即研究第四组元元素对Co-Al-W基合金组织与性能的影响。其中，Xue等[13]研究表明，Ti和Ta的交互作用能够显著提高Co-7Al-8W-1Ta-4Ti单晶高温合金的蠕变性能，使合金在982℃、248 MPa下的蠕变寿命介于第一代和第二代镍基单晶高温合金之间。上述研究揭示了主要合金元素的作用，为发展具有更高承温能力的新型高温结构材料奠定了基础[49]，但不含Ni的Co-Al-W基高温合金较窄的γ + γ'两相区限制了其合金化的空间，使其综合性能难以突破。因此，简单组元的Co-Al-W基合金多作为模型合金进行基础理论研究，工程应用价值较低。

2.1.2 不含W的合金体系

典型的Co-Al-W三元合金中W含量为9%~10% (质量分数约为26%)，这导致合金密度较高，阻碍了其向实用型合金的发展。使用Al、Ti、Mo、Nb和Cr等替代W元素可有效降低合金密度，同时保持一定的γ′相强化和固溶强化效果。因此，钴基高温合金中W含量有逐渐降低的趋势，并出现了一些不含W的合金体系，以获得更好的减重效果。其中，具有代表性的有Co-Al-Mo[39]、Co-Al-Ta[50]、Co-Al-V[51]、Co-Ti-V[52]、Co-Ti-Cr[53]、Co-Ni-Al-Ti[16]等合金体系。这些不含W的钴基高温合金同样具有γ + γ′两相组织，同时具有良好的高温强度和较低的合金密度，为钴基高温合金的发展提供了新的思路。但是，这些合金的γ′相溶解温度普遍低于1100℃，严重制约了合金的承温能力。因此，不含W的合金体系更适于在服役温度和部件密度要求较低的条件下应用。

2.1.3 CoNi基合金体系

Shinagawa等[3]发现Ni的添加可有效提高Co-Al-W基合金的组织稳定性，并拓宽γ + γ'两相区，这为该类合金的发展与应用指明了新的方向。目前，钴基高温合金的研究已向综合性能更好的多组元CoNi基合金发展。这些合金一般含有25%~35%的Ni元素，还含有一定量的Ti、Ta、Cr、Mo和Nb等主要元素。其中，具有代表性的有Eggeler等[28]开发的六元单晶合金、Forsik等[54]开发的具有优异抗氧化性能的六元CoNi基多晶合金、Neumeier等[31]开发的CoW系列变形合金和Volz等[55]开发的ERBOCo系列单晶合金、Pandey等[29]开发的Co-Ni-Al-Mo-Nb-Ti-Ta-Cr系列合金、Knop等[56]开发的不含W的多组元CoNi基变形合金等。此外，本课题组针对航空发动机涡轮叶片和涡轮盘两类部件用材料，分别发展了综合性能佳的多组元CoNi基单晶合金[41]和变形合金[40]。上述多组元CoNi基合金均具有良好的综合性能，并且多数性能已经接近工程应用需求，具有良好的应用前景。

2.2 合金设计方法的发展现状和趋势

2.2.1 传统合金设计方法

钴基高温合金发展初期，由于缺乏热力学数据库，合金设计主要以传统“试错法”为主，即通过研究不同成分合金的组织和性能来理解各合金元素的作用，从而指导合金设计。过去的十几年里，日本东北大学、京都大学，美国密歇根大学、加州大学圣塔芭芭拉分校、西北大学、国家标准技术研究院(National Institute of Standards and Technology，NIST)，德国埃朗根-纽伦堡大学，英国帝国理工大学和印度科学学院等国际知名研究机构[6,39,43,57~59]；以及我国的北京科技大学、清华大学、北京航空航天大学、厦门大学、兰州理工大学、西北工业大学、中南大学、东北大学、天津大学、中国科学院金属研究所、钢铁研究总院和北京航空材料研究院等高校和科研院所[18,60~67]，对该类合金的相平衡、组织稳定性、物理性能、力学性能、氧化腐蚀机理、合金元素作用与新合金开发等方面开展了大量的研究工作。在初步理解其合金化原理的基础上，由低组元合金逐渐发展为具有一定综合性能的多组元合金[13,14,28,31]。但是，使用上述传统“试错法”进行合金开发的工作量大、周期长、成本高，不利于推动该类合金的快速发展和应用。

2.2.2 热力学计算与第一性原理计算的引入

(1) 热力学数据库的开发与应用

随着钴基高温合金的研发，其热力学数据库逐渐得到开发，通过相图计算辅助合金设计的方法也开始使用。例如，美国CompuTherm公司开发了钴基高温合金专用热力学数据库PanCobalt，这也是该类合金最早的商用热力学数据库[68]。另外，瑞典Thermo-Calc公司开发的镍基高温合金专用数据库TCNI8中也包含了Co-Ni-Al-Ti-W-Ta六元系中部分二元系和三元系的热力学参数[36]。

我国也开展了钴基高温合金的热力学研究工作。刘兴军等[61]在大量钴基合金二元系和三元系相平衡研究工作的基础上，对Co-X (X = Ni、Al、W、Ta、Cr等)二元系以及三元系相图进行了热力学优化与计算，并借助Thermo-Calc软件建立了钴基高温合金的热力学数据库。Chen等[69]和Zhou等[70,71]针对钴基高温合金中重要的Co-Al-Ti、Co-Ni-Ti和Co-Ni-Ta等合金体系等温截面图和液相面投影图进行了实验研究，并基于Pandat软件，开展了相关的热力学数据库开发工作。杨舒宇[72]主要针对Co-Ni-Cr、Co-Cr-W、Co-Al-Cr、Co-Al-W和Co-Ni-Al-W等合金体系进行了热力学分析工作，并建立了Co-Ni-Al-W-Cr多元合金的热力学数据库。

随着钴基高温合金热力学数据库的逐渐完善，相图计算也被应用于该类合金的研发。例如，Lass等[36]计算了Ni、Al、W、Ti和Ta等元素对相平衡和γ'相溶解温度的影响，并以此指导合金设计，研制了γ'相溶解温度接近1270℃的六元合金。Ruan等[73]应用上述数据库和软件，并与机器学习方法相结合，设计出了具有较宽γ + γ'两相区、低密度和良好高温强度的Co-V-Ta系列合金。本课题组Li等[35]和Zhuang等[74]在相图计算的辅助下，分别设计出了在1150℃、1000 h仍具有很好γ/γ'两相组织稳定性的六元合金和综合性能佳的七元合金，加速了多组元CoNi基合金的开发。

(2) 第一性原理计算的应用

在钴基高温合金研发早期，研究学者即使用第一性原理计算预测了γ'-Co3(Al, W)相的稳定性和弹性性能等性质。Jiang[75]研究发现，γ'-Co3(Al, W)是一种热力学不稳定相，容易分解为B2结构的β-CoAl相和D019结构的χ-Co3W相，与后续实验研究[76]相吻合。随后，Chen和Wang[77]研究表明，Mo、Ta、Pt、Ni、Fe、V和Ti等元素均能提高γ'相的稳定性；此外，Co3(Al, W)的弹性模量和理论强度均高于Ni3Al，这也与实验结果相吻合。Xu等[78]研究了Co3X (X = Ti、Ta、W、V、Al)的相稳定性，发现L12结构的Co3Ti和D019结构的Co3W均为稳定态，而L12结构的Co3Ta、Co3Al、Co3V则为亚稳态。Gao等[79]研究了Co-X (X = Al、Mo、Nb、Ta、Ti、V、W)和Co-Ti-X (X = Al、V、Cr、Mo、Ta、W)的形成能与晶格参数，结果表明Co3Ti具有最高的γ'相稳定性，而Mo可以显著提高其γ'相稳定性，且Co-Ti-Mo三元合金的γ'相溶解温度超过1150℃。上述工作为发展不含W的合金体系奠定了基础。

2.2.3 高通量实验方法加速研究合金化原理

(1) 多组元扩散多元节方法加速研究合金化原理

扩散多元节实验方法属于一种典型的高通量实验方法，通过该方法可以实现材料高通量设计、表征以及相图的快速测定[80]。Suzuki等[81]最先采用该方法进行了钴基高温合金的研发，并申请了相关专利。Zhu等[62]则测定了Co-Al-X (X = W、Mo、Nb、Ni、Ta)三元合金体系的等温截面相图。Li等[5,82]对传统扩散多元节方法进行了改良，针对多组元CoNi基合金，发展了一种基于复杂多组元扩散多元节的高通量实验方法。在此基础上，快速研究了γ和γ'相形成元素对高温组织稳定性的影响规律，揭示了该合金体系的合金化原理；并针对工程应用合金，发展了一种基于显微组织逆向设计的合金成分快速筛选方法，如图4[5,26]所示。在Li等[5,82]工作基础上，Zou等[41]和Zhuang等[40]分别针对航空发动机涡轮叶片和涡轮盘的材料特点设计了2种CoNi基多组元扩散多元节，进一步研究了该合金体系的合金化原理。除了可快速研究合金化原理与优化合金成分外，多组元扩散多元节还可快速积累实验数据。他们基于上述复杂多组元扩散多元节的工作，建立了合金成分和显微组织量化关系的实验数据库(超过5600组实验数据)，是目前已公开报道的最大的钴基高温合金显微组织(相组成、γ'相体积分数、γ'相尺寸、γ'相球形度等)实验数据库。

图4

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图4   基于显微组织逆向设计的复杂多组元钴基合金成分设计方法示意图[5,26]

Fig.4   Schematics of alloy design for multi-component Co-based superalloys based on multicomponent diffusion-multiple[5,26]


(2) 离子沉积技术快速筛选抗氧化合金

利用离子沉积技术可以制备具有成分梯度的薄膜，可用于加速探索成分、组织和性能之间的对应关系。Stewart等[83]利用该方法制备了一系列具有不同成分梯度特点的Co-Ni-Al-W-Cr-Ta系高温合金薄膜，采用光激发荧光谱(photo-stimulated luminescence spectroscopy，PSLS)技术高通量表征了Ni、Al、Cr和W等元素梯度变化对合金组织和抗氧化性能的影响，并筛选出了在1100℃下具有良好抗氧化性能的合金成分区间。Fan等[84]利用多弧离子镀技术在Co-9Al-9W-2Ta合金基体上高通量制备了具有Al、Cr成分梯度的涂层，并对其抗热腐蚀性能进行了高通量表征。结果表明，随着Al含量的降低，腐蚀产物中α-Al2O3含量明显下降，而α-Cr2O3含量显著增加。

2.2.4 数据驱动的多组元合金快速筛选

计算机技术的高速发展使人工智能技术和高通量计算技术逐渐融入材料科学的研究中，而这也对材料专用数据库提出了更高的要求。目前，日本国立材料研究所(National Institute for Material Science，NIMS)和美国NIST等研究机构均建立了不同领域的材料组织和性能数据库，我国也已设立相应的大数据网站“材料基因工程专用数据库”(www.mgedata.cn)，并于2019年发布了全球首个材料基因工程通则标准[85]。

近年来，研究人员基于材料基因工程的理念，将机器学习方法引入到钴基高温合金的研发中，并取得了一定的成果[86]。Liu等[87]采用该方法进行了新合金的设计，首先基于文献和课题组的实验数据建立了组织稳定性、γ'相溶解温度、合金密度等预测模型；然后，在多性能筛选、全局优化算法和实验反馈的策略指导下，获得了γ'相溶解温度超过1260℃，且具有较高高温组织稳定性和一定抗氧化性能的七元合金。Zou等[41]、Lu等[88]和Zhuang等[40]结合多组元扩散多元节与机器学习方法，建立了显微组织数据库及其预测模型，并基于多目标优化的策略进行了合金成分的快速筛选，针对航空发动机涡轮叶片和涡轮盘两类部件用材料，分别发展了性能优异的九元CoNi基单晶和变形高温合金。Yu等[89]也利用机器学习辅助合金设计的方法获得了兼具较高γ'相溶解温度、γ'相体积分数和较低密度的八元合金。利用以上机器学习和实验数据相结合的方法进行新合金设计可以有效缩短合金开发周期，并实现复杂合金体系的多目标优化。因此，上述方法对未来工程应用合金的成分优化和新型合金的开发具有重要意义。

3 钴基高温合金的蠕变性能与变形机制

蠕变性能是高温构件设计、选材和安全评价必须要考虑的最基本和最重要的高温力学性能之一。为追求更高的承温能力，国内外针对钴基高温合金的蠕变性能和主要变形机制进行了一系列研究[57,90~94]。研究表明，早期研究的简单组元Co-Al-W基单晶高温合金和近年来发展的面向工程应用的复杂多组元CoNi基单晶高温合金的蠕变性能均与第一代镍基单晶高温合金相当，如图5[12,13,90,93,95,96]所示。蠕变抗力方面，目前Co-Al-W基和CoNi基合金的研究多集中于900℃及以下[10,92,95]。本节将重点介绍钴基单晶高温合金蠕变机理方面的主要研究成果和不足。

图5

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图5   Co-Al-W和CoNi基单晶高温合金与镍基单晶高温合金蠕变性能[12,13,90,93,95,96]

Fig.5   Creep properties of γ′-strengthened Co (Co-Al-W/CoNi)- and Ni-based single crystal superalloys[12,13,90,93,95,96] (T—temperature (K), tr—rupture life (h))


3.1 合金元素对蠕变性能的影响

为提高钴基高温合金的蠕变性能，多种合金元素被引入到该类合金中。研究表明，W、Ti、Ta、Mo等的添加有助于提高蠕变性能[9]，其中又以Ti和Ta的交互作用最为明显(图6[13])；Si对合金的最小蠕变速率无明显影响。需要特别指出的是，为保证良好的环境抗力和合适的密度，在面向工程应用的CoNi基合金中，Al/W的增加会提高γ'相体积分数和抗氧化性能，同时显著降低密度，对调控合金蠕变性能具有主要作用。然而，Cr对CoNi基合金蠕变性能的影响仍存在争议。Titus等[97]研究表明，在982℃条件下，低Cr含量CoNi基单晶合金的蠕变抗力明显高于高Cr合金，但在900℃条件下则完全相反。本课题组初步研究也表明，高Cr低γ'相体积分数单晶合金1000℃、137 MPa条件下的蠕变性能优于低Cr高γ'相体积分数合金。这应与Cr的固溶强化作用及其对γ'相体积分数的影响有关，相关机制仍有待进一步研究。

图6

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图6   Ti和Ta元素对Co-Al-W基单晶高温合金蠕变性能的影响[13]

Fig.6   Effect of Ti and Ta elements on creep properties of Co-Al-W-based single crystal superalloys[13]


3.2 微观组织对蠕变性能的影响

与镍基高温合金的研究类似，γ'相体积分数是影响钴基高温合金蠕变性能的最主要因素。有限的研究[57,95]表明，随着γ'相体积分数增大，蠕变寿命提高，且高蠕变抗力Co-Al-W/CoNi基单晶高温合金的γ'相体积分数一般都接近或超过75%，高于镍基单晶高温合金(60%~70%)。对比γ′相体积分数，γ'相尺寸对蠕变寿命的影响规律则更为复杂，但一般与δ相关。初步研究[7]表明，δ的绝对值越大，蠕变寿命对γ'相尺寸的变化越敏感。当δ绝对值较大时，γ'相的最佳尺寸范围较窄；δ绝对值较小时，γ'相的最佳尺寸范围变宽。

除上述参数外，在蠕变过程中，γ'相的定向粗化(筏排)也会对合金的蠕变抗力产生影响。一般来说，δ绝对值越大，筏排组织形成越快。在高温拉应力条件下，正错配度的钴基单晶高温合金会形成与拉应力轴平行的筏排组织(P-型筏排)，与负错配度镍基单晶高温合金的情况完全相反。此外，在已报道的钴基单晶高温合金中，其γ'相体积分数一般均超过60%；随着蠕变进行，γ'相发生持续粗化和连接，使γ相分布在连续的γ'相“基体”中，又称拓扑反转组织(topological inversed microstructure)，如图7[98]右上角红圈所示。

图7

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图7   正错配度Co-Al-W基单晶高温合金高温拉伸蠕变过程中的微观组织演变[98]

Fig.7   Microstructural evolutions during the tensile creep process of a Co-Al-W-based single crystal superalloys with the positive misfit at 900oC and 420 MPa[98] (Insets show the γ/γ' microstructures during the creep process, and the red circles indicate the topological inversed microstructure. σ—stress)


对比负错配度的镍基高温合金拉伸蠕变过程中形成的垂直于应力轴的筏排组织(N-型筏排)，有关2种类型筏排组织对蠕变抗力的影响目前仍存在争议。相关研究[23]表明，N-型筏排组织较P-型更能提高蠕变抗力。但也有研究[99]表明，低应力条件下，位错在P-型筏排组织中的攀移速率更低。针对该问题，Chung等[100]研究了筏排方向对正错配度的钴基单晶高温合金拉伸蠕变抗力的影响。结果显示，N-型和P-型筏排组织均能提高合金蠕变初期的变形抗力，但均会缩短蠕变稳态阶段寿命，尤其是N-型筏排组织。

3.3 γ′相中形变亚结构形成与演变机制

(1) 层错

钴基高温合金蠕变过程中最常见的形变亚结构为γ'相中的层错(SF)。但是，与镍基高温合金中温(700~850℃)高应力(> 550 MPa)蠕变过程中广泛报道的由a<112>型位错组成的超点阵内禀层错-反相畴界-超点阵外禀层错(superlattice intrinsic stacking fault-antiphase boundary-superlattice extrinsic stacking fault，SISF-APB-SESF)复杂层错带状结构不同[101]，相关的发现多以单独的SISF和SESF为主，涉及的主要形成机制有2种。第1种为<112>型位错的滑移机制：

a / 2<112> →a / 3<112> + SISF+a / 6<112>

领先不全位错a / 3<112>切入γ'相，并在其中留下单独的SISF结构，拖尾不全位错a / 6<112>则停留在γ/γ′相界面上，否则将在γ'相中形成能量较高的APB结构。Lenz等[102]研究发现，该领先不全位错实际由位于相邻{111}面上的3个位错核心组成，如图8a[102]和c右上角黑色和蓝色位错所示。涉及的主要位错反应为：

图8

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图8   钴基单晶高温合金γ'相中超点阵内禀层错(SISF)[102]和超点阵外禀层错(SESF)[91]的原子结构及其形成机制模型图

Fig.8   Atomic structures of superlattice intrinsic stacking fault (SISF) (a)[102] and superlattice extrinsic stacking fault (SESF) (b)[91] in the γ' phase as well as their schematic formation mechanisms (c) in γ'-strengthened Co-based single crystal superalloys (Inset in Fig.8a shows a center-of-symmetry map of the structure. LPD—leading partial dislocation, ISF—intrinsic stacking fault, APB—antiphase boundary, CISF—complex intrinsic stacking fault)


a / 2<110> →a / 6<121¯>+ CISF+a / 6<211>

复杂内禀层错(complex intrinsic stacking fault，CISF)与相邻{111}面上由2个a / 6<112> Shockley不全位错滑移产生的APB发生交互作用，部分原子重新排列，使能量较高的CISF + APB的双层结构转化为稳定的SISF结构。类似地，SESF的领先不全位错由位于相邻{111}滑移面的2个CISF交互作用生成[91]，如图8b[91]和c右下角所示，但目前上述交互作用的具体过程仍有待进一步阐明。

除滑移机制外，a / 3<111> Frank不全位错在γ'相中的攀移运动也会形成SISF或SESF结构。对比图8c所示的滑移机制，经攀移形成的层错无须经历部分原子的重新排列。上述过程涉及的位错反应为：

a / 2<110> →a / 3<111>+ SISF/SESF+a / 6<112¯>                             

其中，a / 3<111>属于纯刃型位错，无法进行滑移过程。经滑移和攀移机制形成的SISF在原子排布方面完全相同，仅领先不全位错存在差异。前者为三核心结构(3个a / 6<211>)，后者为单核心结构(a / 3<111>)。

(2) 层错交互作用

在实际蠕变过程中，SISF和SESF均可在多个晶体学平面上形成，从而形成复杂的交互作用结构。Lu等[91]根据形貌将交互作用结构分为3类(V-型、T-型和X型) (图9a[91])，并系统研究了其形成机制。其中，V-型结构一般由2个位于不同{111}滑移面(非平行)的层错构成，在2个滑移面交线处形成不可动的压杆位错，提高蠕变抗力。主要形成机制有2种，涉及的基本位错反应分别为：

图9

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图9   Co-Al-W基单晶高温合金γ'相中形成的不同类型的层错交互作用结构[91]

Fig.9   Different types of stacking fault (SF) interaction configurations in Co-Al-W-based single crystal superalloys[91]

(a) TEM image

(b-d) atomic resolution HAADF-scanning transmission electron microscopy (HAADF-STEM) images of V-type (b), T-type (c), and X-type (d) (Inset in Fig.9c shows an enlarged view of the red square, indicating a deviation between the SISF-2 and SISF-2′ planes)


a / 6<211¯> →a / 3<001¯>+ a / 6<211>
a / 6<2¯1¯1>+ a / 6<211> →a / 3<001>

第一种是通过单个领先不全位错在不同滑移面的交滑移产生；另一种则是通过位于2个不同滑移面的领先不全位错在对应滑移面的交线处反应生成。但是，后者需要2个不全位错恰好在2个{111}面的交线相遇，发生的概率较小，与实验观察不符。因此， 式(4)被认为是形成压杆位错(P)的主要机制，其基本原子结构如图9b[91]所示。此外，研究结果还发现，SESF对应的2个领先不全位错，在交滑移过程中，仅有一个能够发生交滑移，最终形成由SESF和SISF构成的V-型结构。对比V-型结构，T-型结构的形成则较为简单，层错领先不全位错运动到另一滑移面层错附近时，会发生交互作用，阻碍不全位错的继续运动并使层错面发生一定程度的偏移(图9c[91])。如果领先不全位错的运动速率足够大，则将会穿透层错面，形成X-型层错交互作用结构。T-型和X-型结构中的2个层错均可由SISF和SESF构成，但一般认为SESF较SISF更难穿透[103]。因此，X-型层错交互作用结构多由2个SISF组成，如图9d[91]所示。

根据式(1)~(3)，当SISF的领先和拖尾不全位错先后切入γ′相后，即会在拖尾位错后形成APB，从而形成SISF-APB的共生结构(图10(1)~(3)[28])。而且，该结构会进一步演变为拖尾不全位错环包裹的SISF，最终形成APB-SISF-APB结构，其形成机制示意图如图10(4)和(5)所示。除上述结构外，Lenz等[102]和Lu等[104]分别在研究CoNi和Co-Al-W基单晶合金蠕变过程时，发现了SISF-APB-SISF和连续的…-SISF-APB-…等更加复杂的共生结构，推测这可能与位错处的合金元素偏析有关，相关的形成机制仍有待进一步研究。

图10

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图10   CoNi基单晶高温合金中反相畴界-超点阵内禀层错-反相畴界(APB-SISF-APB)结构的形成机制示意图[28]

Fig.10   Formation mechanism of APB-SISF-APB configuration in CoNi-based single crystal superalloys[28] ((1) two closely spaced Shockley partials approach the γ' phase on the (111) glide plane. (2) the leading partial enters the γ' phase, forming a SISF. (3) the trailing partial also enters the γ' phase, transforming the SISF into an APB. (4) the leading partial shears through the entire γ' phase, and the trailing partial forms a closed loop inside the γ' phase. (5) both of leading and trailing partials shear through the entire γ' phase, and partial dislocation loop surrounds an SISF and is embedded in an APB. The bottom-right corner right shows the corresponding dislocation schematic of SISF→APB transformation in the γ' phase. a—lattice constant of γ' phase, FL—dislocation line tension, Fτ —glide force resulting from the resolved shear stress, Ff—net force originating from difference between the APB and SISF energies, bAPB—Burgers vector of APB, bSISF—Burgers vector of SISF)


综合考虑蠕变过程中的微观组织和层错等形变亚结构的演变及其交互作用，Lu等[90]系统总结了钴基单晶高温合金高温低应力条件下的拉伸蠕变机理，如图11[90]所示。蠕变行为方面，正错配度的钴基单晶高温合金一般会产生额外的稳态蠕变阶段(阶段Ⅲ)，且稳态蠕变速率高于阶段Ⅱ的最小蠕变速率，而负错配度的镍基单晶高温合金一般不存在额外的稳态蠕变阶段，其最小蠕变速率即为稳态蠕变速率。微观组织演变方面，由于错配度差异，钴基和镍基单晶高温合金分别形成平行和垂直于拉伸应力轴的筏排组织。形变亚结构演变方面，2种合金在高温低应力拉伸蠕变初期(阶段I和阶段Ⅱ)的变形机理无明显差异，主要受筏排组织的形成和基体/界面位错控制。随着蠕变进行，钴基高温合金由于具有较低的层错能，其γ'相中层错及其交互作用结构的出现是产生额外稳态(阶段Ⅲ)和后续加速(阶段Ⅳ)蠕变阶段的主要原因，而在镍基单晶高温合金中则是大量位错对切割γ′相，直接形成加速蠕变阶段。

图11

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图11   钴基单晶高温合金高温低应力拉伸蠕变条件下不同阶段微观组织和形变亚结构演变的模型图[90]

Fig.11   Schematic representations of the evolution of the γ/γ' microstructure and dislocation substructure in a γ'-strengthened Co-based single crystal superalloy during the deceleration (a), the minimum stable (b), onset of the global stable (c), near the end of the global stable (d), and the acceleration tensile creep (e) stages[90]


3.4 合金元素偏析对蠕变抗力的影响

近年来，随着高分辨球差电镜和三维原子探针等先进表征技术的发展，研究[105]发现，合金元素不仅在高温合金γ/γ'两相中存在偏析；在变形过程中，位错和层错等附近也存在合金元素偏析，并可对合金的微观组织演变、形变亚结构形成和发展等过程产生影响，进而影响合金的蠕变抗力。目前，相关理论[105,106]已用来解释镍基高温合金γ/γ'相界面稳定性、γ'相粗化、中温和高温蠕变抗力和疲劳损伤等关键问题。针对钴基高温合金，相关研究[28,91,94]主要集中于蠕变过程中γ'相形变亚结构处的合金元素偏析行为。

3.4.1 层错能和反相畴界能演变

合金元素在形变亚结构处的富集会直接影响其形成能，进而影响形变抗力。Zhang等[107]和Wang等[108]针对钴基高温合金蠕变过程中形成的SF和APB，基于第一性原理计算进行了较为系统的研究，如图12[107,108]所示。研究表明，W、Re、Mo和Cr的添加有利于降低γ'相的层错能，但会提高γ'相的反相畴界能。Ni的添加有助于提高层错能，但会显著降低反相畴界能；而Ti和Ta则提高层错和反相畴界能。合金元素对2种形变亚结构形成能影响程度的排序分别为，层错能(Co3TM0.25)：Ti > Hf > Pt > Ni > Rh > Ta > V > Fe > Zr > Nb > Ru > Mn > Cr > Mo > Re > Y > W (图12a)[107]；反相畴界能(Co3Al0.75TM0.25)：Mo > W > Re > Cr > Hf > Ti > Y > Ta > Ru > Ni > Al (图12b)[108]。Titus等[109]结合理论计算证明，层错处W等元素的偏聚会降低层错领先不全位错切入γ'相的临界应力。同时，根据不同类型合金中的形变亚结构，Titus等[57]推测，镍基高温合金具有较高的层错能，Co-Al-W基高温合金具有较高的反相畴界能，而CoNi基高温合金则介于2者之间。因此，CoNi基高温合金中更容易出现由SF和APB组成的复杂形变亚结构。

图12

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图12   合金元素对γ'相层错能(Co3TM)[107]和反相畴界能(Co3Al0.75TM0.25)[108]的影响

Fig.12   Influence of alloying elements on the SF (Co3TM) (a)[107]and APB (Co3Al0.75TM0.25) (b)[108] energies of γ' phase (ANNI—axial nearest-neighbor Ising, γAPB—APB energy, FP—first-principles calculation, Exp.—experiment)


3.4.2 局部相转变行为

根据合金元素类型，元素偏析不仅影响层错和反相畴界能，还可能对合金的微观组织演变产生作用；而且Co-Al-W基和CoNi基合金存在明显差异。在高温蠕变过程中，前者层错处偏聚的合金元素主要以W为主[91,110]；后者则多以Co和Cr为主[28,94]，与镍基合金中温高应力的情况较为类似[105]。层错的类型(SISF/SESF)对合金元素的偏析行为无明显影响。结合合金元素偏析行为和SISF/SESF的原子点阵结构，Titus等[110]和Lu等[91]认为层错处的合金元素偏析会诱导Co-Al-W基合金γ'相的SISF/SESF向χ/η相转变。在此基础上，Titus等[110]结合热力学和第一性原理计算，分析了SISF→χ相转变和一般相转变过程的区别。前者较后者需要更少的χ相形成元素(W)，这一特征使其更容易成为χ相的形核位点。CoNi基合金方面，由于其层错处主要偏析Co和Cr等γ相形成元素，与χ相的形成关系不大。结合图12[107,108]所示的研究成果，χ/η相形成元素(W、Ta、Nb等)的偏聚会明显提高反相畴界能，从而抑制拖尾不全位错切入γ'相，提高蠕变抗力；而Co和Cr等元素的偏析对反相畴界能的影响不如W等元素明显。因此，CoNi基合金γ'相中较易形成SISF-APB共生结构，这与实验结果[28]相符。

另一方面，结合上述局部相转变理论，考虑复杂层错(complex stacking fault，CSF)和超点阵层错(superlattice stacking fault，SSF)原子点阵结构的相似性，Barba等[111]提出，CISF和复杂外禀层错(complex extrinsic stacking fault，CESF)处的合金元素偏析会诱导2种结构附近的原子发生重新排列(有序化)，进而发生CISF→SISF和CESF→SESF转变，如图13a[111]所示。Lu等[104]则在Co-Al-W基单晶高温合金高温低应力蠕变过程中也发现了a / 6<112>Shockley不全位错(CISF典型领先不全位错)连接的SISF结构(图13b[104])，进一步验证了上述理论。

图13

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图13   γ'相中层错附近合金元素偏析诱导缺陷类型转变模型[111]和与SISF相连的Shockley不全位错[104]

Fig.13   Segregation-assisted transformation from complex stacking faults (CSFs) to superlattice stacking faults (SSFs) (a)[111] and SISF bounding by a Shockley partial dislocation in the γ' phase (b)[104] (CESF—complex extrinsic stacking fault, Inset in Fig.13b shows the Burgers vector ( b ) obtained from the Burgers circuit analysis)


除层错外，Lu等[91]和Makineni等[112]的研究发现，钴基单晶高温合金中层错的领先不全位错处主要富集γ相形成元素。目前，有关合金元素偏析对层错扩展的影响仍存在争议。Makineni等[112]认为合金元素沿层错方向上的扩散是影响其在γ'相中扩展的关键因素。Titus等[109]和Lenz等[102]则认为层错在γ'相中形成后，合金元素偏析即迅速发生，与扩散方向无明显关系。Lu等[91]研究认为，对比合金元素在层错上的扩散，层错领先不全位错处的Cottrell气团对层错扩展的影响更为重要。这可能与合金具体的成分特征有关，需结合合金元素的具体偏析程度和类型进行深入研究。

除此之外，Lu等[91,104]和Lenz等[94]研究发现，层错交截和层错领先不全位错处γ相形成元素的富集均会诱导局部的γ'相向γ相(γ'→γ)转变，如图14[94,104]所示。在此基础上，He等[113]研究发现，当领先不全位错运动至γ/γ'相界面时，也会携带部分γ'相形成元素至γ相，诱导局部γ'相形核，使γ'相沿层错面方向粗化连接，最终形成平行于{111}面的筏排组织，从而影响筏排组织的完整性，降低蠕变性能。目前，有关上述相变过程的热力学机制及其对后续蠕变行为的影响仍未见报道。

图14

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图14   γ相形成元素偏析诱导的γ'→γ相转变[94,104]

Fig.14   Segregation-assisted γ'→γ transformation in the γ'-strengthened Co-based single crystal superalloys (Insets show the fast Fourier transform (FFT) spectra confirming the ordered and disordered structure in the γ' and γ' regions)

(a) leading partial dislocation in a Co-Al-W-based single crystal superalloy[104]

(b) SF interaction in a CoNi-based single crystal superalloy[94]


综上所述，对比具有负错配度的典型镍基高温合金和具有正错配度和较低层错能的钴基高温合金，2种合金的高温蠕变行为和主要强化机制存在明显差异；同时，考虑钴基高温合金的成分特点，该类合金的高温低应力蠕变强化机制与镍基高温合金中温高应力的情况较为类似；层错处合金元素的偏析行为会影响γ'相中形变亚结构的形成过程，促进或抑制SF和APB的扩展，进而影响合金的蠕变抗力。此外，合金元素偏析诱导的局部相转变对合金组织稳定性和变形机制的影响仍需要进一步深入研究。

4 总结与展望

先进高温结构材料的研发是国家工业发展的重要基础。经过十余年的研究，国内外研发人员在钴基高温合金基础研究和应用基础研究方面取得了一定的进展。与国外相比，国内在成分-组织-性能关联性和数据积累方面具有一定优势。在合金设计方面，结合材料基因工程理念，采用扩散多元节等高通量实验方法耦合大数据和机器学习技术，高效研究并揭示了钴基高温合金的合金化原理；在变形机理方面，采用多尺度的表征方法，发现了与负错配度的镍基高温合金明显不同的高温蠕变变形行为，揭示了正错配度、低层错能的钴基高温合金高温蠕变变形和层错强化机理，为该类合金的进一步优化提供了理论基础。在此基础上，进一步地形成了综合考虑合金组织稳定性、力学性能、氧化性能、密度等多项工程应用关键指标的合金成分设计与优化方法。目前开发的多组元钴基高温合金已接近工程应用水平，展现出了良好的工程应用前景。

为全面满足工程应用需求，钴基高温合金的综合性能仍有进一步优化的空间，特别是在高温蠕变/疲劳性能、抗氧化/腐蚀性能、铸造性能、热加工性能、经济性等方面。因此，仍需进行如下几方面的基础和应用基础研究工作：(1) 继续结合高通量实验方法和机器学习技术，深入研究多合金元素交互作用机理；(2) 在高温蠕变机理研究工作的基础上，加强合金中温蠕变、疲劳损伤等强韧化机理研究；(3) 针对大尺寸/复杂形状构件，开发合金组织和缺陷控制技术，揭示钴基高温合金制备过程中的物理冶金原理；(4) 面向高承温能力的变形合金，研究热机械加工工艺对钴基高温合金显微组织的影响机制及组织性能关系微观机理；(5) 有应用潜力的钴基铸造和变形高温合金的研发与综合性能研究；(6) 针对该类合金的本征特性，开展相应的工程服役匹配性研究，拓展可能的应用方向。例如，机匣材料、3D打印材料、丝材和棒材等也是未来需要探索和关注的重点研究方向。

总之，钴基高温合金的发展需要综合考虑合金设计、制备加工、服役安全和经济成本控制等方面的科学与技术问题，深度结合工业生产和工程部件服役的实际需求，实现材料研发、部件制备、工程应用的协同发展，加速钴基高温合金的工程应用进程，为我国航空航天、能源动力、交通运输等领域关键热端部件的自主研制提供材料支撑。

参考文献

Sato J, Omori T, Oikawa K, et al.

Cobalt-base high-temperature alloys

[J]. Science, 2006, 312: 90

PMID      [本文引用: 9]

We have identified cobalt-base superalloys showing a high-temperature strength greater than those of conventional nickel-base superalloys. The cobalt-base alloys are strengthened by a ternary compound with the L1(2) structure, gamma' Co3(Al,W), which precipitates in the disordered gamma face-centered cubic cobalt matrix with high coherency and with high melting points. We also identified a ternary compound, gamma' Ir3(Al,W), with the L1(2) structure, which suggests that the Co-Ir-Al-W-base systems with gamma+gamma' (Co,Ir)3(Al,W) structures offer great promise as candidates for next-generation high-temperature materials.

ZXGG-SK01-8-2020 process specification for a precision casting of a Co-based single crystal turbine first-stage working blade [S]. 2020

[本文引用: 1]

ZXGG-SK01-8-2020 新型钴基单晶合金透平一级工作叶片精铸件工艺规程 [S]. 2020

[本文引用: 1]

Shinagawa K, Omori T, Sato J, et al.

Phase equilibria and microstructure on γ' phase in Co-Ni-Al-W system

[J]. Mater. Trans., 2008, 49: 1474

DOI      URL     [本文引用: 8]

Cui C Y, Ping D H, Gu Y F, et al.

A new Co-base superalloy strengthened by γ' phase

[J]. Mater. Trans., 2006, 47: 2099

DOI      URL     [本文引用: 1]

Li W D, Li L F, Wei C D, et al.

Effects of Ni, Cr and W on the microstructural stability of multicomponent CoNi-base superalloys studied using CALPHAD and diffusion-multiple approaches

[J]. J. Mater. Sci. Technol., 2021, 80: 139

DOI      [本文引用: 6]

The alloying effects of Ni, W and Cr on the microstructural stability of CoNi-base alloys were investigated using a multicomponent diffusion multiple after being aged at 1000 °C for 1000 h. The diffusion multiple was carefully designed based on thermodynamic calculations. The relationships between alloy compositions and microstructural characteristics were established over a large compositional range using this single sample, and the alloying effects of Ni, W and Cr on the elemental partitioning behaviors between γ and γ′ two phases were thermodynamically analyzed using high-throughput calculation. The results together show that an increase of Ni content increases the γ′ volume faction in the long-term aged microstructures. However, the higher Ni content leads to the precipitation of the χ phase by promoting the partitioning of W from the γ′ phase to the γ phase. The decrease of W content dramatically reduces the γ′ volume faction, but the addition of Cr can properly counteract this effect by promoting the partitioning of Al and Ti from the γ phase to the γ′ phase. This study will be helpful for accelerating the development of novel γ′-strengthened multicomponent CoNi-base alloys, as well as providing experimental data to improve the thermodynamic database.

Ooshima M, Tanaka K, Okamoto N L, et al.

Effects of quaternary alloying elements on the γ' solvus temperature of Co-Al-W based alloys with FCC/L12 two-phase microstructures

[J]. J. Alloys Compd., 2010, 508: 71

DOI      URL     [本文引用: 11]

Zhou H J, Li W D, Xue F, et al.

Alloying effects on microstructural stability and γ' phase nano-hardness in Co-Al-W-Ta-Ti-base superalloys

[A]. Superalloys 2016 [C]. Hoboken: Wiley, 2016: 981

[本文引用: 8]

Yan H Y, Vorontsov V A, Dye D.

Alloying effects in polycrystalline γ' strengthened Co-Al-W base alloys

[J]. Intermetallics, 2014, 48: 44

DOI      URL     [本文引用: 6]

Bauer A, Neumeier S, Pyczak F, et al.

Creep strength and microstructure of polycrystalline γ'-strengthened cobalt-base superalloys

[A]. Superalloys 2012 [C]. Hoboken: Wiley, 2012: 695

[本文引用: 3]

Suzuki A, Inui H, Pollock T M.

L12-strengthened cobalt-base superalloys

[J]. Annu. Rev. Mater. Res., 2015, 45: 345

DOI      URL     [本文引用: 13]

Omori T, Oikawa K, Sato J, et al.

Partition behavior of alloying elements and phase transformation temperatures in Co-Al-W-base quaternary systems

[J]. Intermetallics, 2013, 32: 274

DOI      URL     [本文引用: 10]

Titus M S, Suzuki A, Pollock T M.

High temperature creep of new L12 containing cobalt-base superalloys

[A]. Superalloys 2012 [C]. Hoboken: Wiley, 2012: 823

[本文引用: 5]

Xue F, Zhou H J, Feng Q.

Improved high-temperature microstructural stability and creep property of novel Co-base single-crystal alloys containing Ta and Ti

[J]. JOM, 2014, 66: 2486

DOI      URL     [本文引用: 12]

Xue F, Zhou H J, Shi Q Y, et al.

Creep behavior in a γ' strengthened Co-Al-W-Ta-Ti single-crystal alloy at 1000℃

[J]. Scr. Mater., 2015, 97: 37

DOI      URL     [本文引用: 1]

Pyczak F, Bauer A, Göken M, et al.

The effect of tungsten content on the properties of L12-hardened Co-Al-W alloys

[J]. J. Alloys Compd., 2015, 632: 110

DOI      URL     [本文引用: 4]

Gao Q Z, Jiang Y J, Liu Z Y, et al.

Effects of alloying elements on microstructure and mechanical properties of Co-Ni-Al-Ti superalloy

[J]. Mater. Sci. Eng., 2020, A779: 139139

[本文引用: 3]

Fu H D, Zhang Y H, Xue F, et al.

Microstructure and properties evolution of Co-Al-W-Ni-Cr superalloys by molybdenum and niobium substitutions for tungsten

[J]. Metall. Mater. Trans., 2020, 51A: 299

[本文引用: 1]

Xue F, Wang M L, Feng Q.

Alloying effects on heat-treated microstructure in Co-Al-W-base superalloys at 1300oC and 900oC

[A]. Superalloys 2012 [C]. Hoboken: Wiley, 2012: 813

[本文引用: 5]

Reed R C. The Superalloys: Fundamentals and Applications [M]. Cambridge: Cambridge University Press, 2006: 46

[本文引用: 5]

Povstugar I, Zenk C H, Li R, et al.

Elemental partitioning, lattice misfit and creep behaviour of Cr containing γ' strengthened Co base superalloys

[J]. Mater. Sci. Technol., 2016, 32: 220

DOI      URL     [本文引用: 1]

Tanaka K, Ooshima M, Okamoto N L, et al.

Morphology change of γ' precipitates in γ/γ' two-phase microstructure in Co-based superalloys by higher-order alloying

[J]. MRS Online Proc. Libr., 2011, 1295: 423

[本文引用: 5]

Li Y Z, Pyczak F, Stark A, et al.

Temperature dependence of misfit in different Co-Al-W ternary alloys measured by synchrotron X-ray diffraction

[J]. J. Alloys Compd., 2020, 819: 152940

DOI      URL     [本文引用: 1]

Mughrabi H.

The importance of sign and magnitude of γ/γ' lattice misfit in superalloys-with special reference to the new γ'-hardened cobalt-base superalloys

[J]. Acta Mater., 2014, 81: 21

DOI      URL     [本文引用: 4]

Coakley J, Lass E A, Ma D, et al.

Lattice parameter misfit evolution during creep of a cobalt-based superalloy single crystal with cuboidal and rafted gamma-prime microstructures

[J]. Acta Mater., 2017, 136: 118

DOI      URL     [本文引用: 1]

Lass E A, Sauza D J, Dunand D C, et al.

Multicomponent γ'- strengthened Co-based superalloys with increased solvus temperatures and reduced mass densities

[J]. Acta Mater., 2018, 147: 284

DOI      URL     [本文引用: 5]

Zhuang X L, Antonov S, Li L F, et al.

γ'-strengthened multicomponent CoNi-based wrought superalloys with improved comprehensive properties

[J]. Metall. Mater. Trans., 2023, 54A: 1671

[本文引用: 6]

Xia W S, Zhao X B, Yue L, et al.

A review of composition evolution in Ni-based single crystal superalloys

[J]. J. Mater. Sci. Technol., 2020, 44: 76

DOI      [本文引用: 1]

Due to the outstanding creep performance, nickel-based single crystal superalloys (Ni-SXs) are extensively applied in modern aero-engine and industrial gas turbine. Apart from the special single crystal structure which is disadvantageous to extension of creep cracks, Ni-SXs derive the creep strength from intrinsic two-phase microstructure (γphase and γ’ phase). Main microstructural parameters including volume fraction of γ’ phase and the lattice misfit, and the formation and distribution of precipitated phase are determined by the compositions of alloys. Besides, the creep properties are greatly influenced by these microstructural parameters and precipitated phase. This review has summarized the relationships between different alloying elements and microstructures and indicated their influence on creep properties of Ni-SXs. In addition, with the improvements of experimental methods and characterization technique, some recent discoveries have provided additional evidence to support or challenge the pervious creep theories of superalloys. In view of these new discoveries, this review has provided some perspectives which can be referenced in future compositional design of Ni-SXs.

Eggeler Y M, Müller J, Titus M S, et al.

Planar defect formation in the γ' phase during high temperature creep in single crystal CoNi-base superalloys

[J]. Acta Mater., 2016, 113: 335

DOI      URL     [本文引用: 9]

Pandey P, Mukhopadhyay S, Srivastava C, et al.

Development of new γ'-strengthened Co-based superalloys with low mass density, high solvus temperature and high temperature strength

[J]. Mater. Sci. Eng., 2020, A790: 139578

[本文引用: 3]

Pollock T M, Dibbern J, Tsunekane M, et al.

New Co-based γ-γ' high-temperature alloys

[J]. JOM, 2010, 62(1): 58

[本文引用: 1]

Neumeier S, Freund L P, Göken M.

Novel wrought γ/γ' cobalt base superalloys with high strength and improved oxidation resistance

[J]. Scr. Mater., 2015, 109: 104

DOI      URL     [本文引用: 3]

Xue F, Zhou H J, Ding X F, et al.

Improved high temperature γ' stability of Co-Al-W-base alloys containing Ti and Ta

[J]. Mater. Lett., 2013, 112: 215

DOI      URL     [本文引用: 5]

Makineni S K, Samanta A, Rojhirunsakool T, et al.

A new class of high strength high temperature Cobalt based γ-γ' Co-Mo-Al alloys stabilized with Ta addition

[J]. Acta Mater., 2015, 97: 29

DOI      URL     [本文引用: 2]

Bocchini P J, Sudbrack C K, Noebe R D, et al.

Effects of titanium substitutions for aluminum and tungsten in Co-10Ni-9Al-9W (at%) superalloys

[J]. Mater. Sci. Eng., 2017, A705: 122

[本文引用: 1]

Li W D, Li L F, Antonov S, et al.

Effective design of a Co-Ni-Al-W-Ta-Ti alloy with high γ' solvus temperature and microstructural stability using combined CALPHAD and experimental approaches

[J]. Mater. Des., 2019, 180: 107912

DOI      URL     [本文引用: 2]

Lass E A.

Application of computational thermodynamics to the design of a Co-Ni-based γ'-strengthened superalloy

[J]. Metall. Mater. Trans., 2017A, 48: 2443

[本文引用: 3]

Li W D, Li L F, Antonov S, et al.

Effects of Cr and Al/W ratio on the microstructural stability, oxidation property and γ' phase nano-hardness of multi-component Co-Ni-base superalloys

[J]. J. Alloys Compd., 2020, 826: 154182

DOI      URL     [本文引用: 1]

Nithin B, Samanta A, Makineni S K, et al.

Effect of Cr addition on γ-γ' cobalt-based Co-Mo-Al-Ta class of superalloys: A combined experimental and computational study

[J]. J. Mater. Sci., 2017, 52: 11036

DOI      URL     [本文引用: 1]

Pandey P, Kashyap S, Palanisamy D, et al.

On the high temperature coarsening kinetics of γ' precipitates in a high strength Co37.6Ni35.4Al9.9Mo4.9Cr5.9Ta2.8Ti3.5 fcc-based high entropy alloy

[J]. Acta Mater., 2019, 177: 82

DOI      URL     [本文引用: 3]

Zhuang X L, Antonov S, Li W D, et al.

Alloying effects and effective alloy design of high-Cr CoNi-based superalloys via a high-throughput experiments and machine learning framework

[J]. Acta Mater., 2023, 243: 118525

DOI      URL     [本文引用: 4]

Zou M, Li W D, Li L F, et al.

Machine learning assisted design approach for developing γ'-strengthened Co-Ni-base superalloys

[A]. Superalloys 2020 [C]. Cham: Springer, 2020: 937

[本文引用: 4]

Caron P.

High γ' solvus new generation nickel-based superalloys for single crystal turbine blade applications

[A]. Superalloys 2000 [C]. Warrendale: TMS, 2000: 737

[本文引用: 4]

Suzuki A, Pollock T M.

High-temperature strength and deformation of γ/γ' two-phase Co-Al-W-base alloys

[J]. Acta Mater., 2008, 56: 1288

DOI      URL     [本文引用: 2]

Meher S, Nag S, Tiley J, et al.

Coarsening kinetics of γ' precipitates in cobalt-base alloys

[J]. Acta Mater., 2013, 61: 4266

DOI      URL     [本文引用: 1]

Vorontsov V A, Barnard J S, Rahman K M, et al.

Coarsening behaviour and interfacial structure of γ' precipitates in Co-Al-W based superalloys

[J]. Acta Mater., 2016, 120: 14

DOI      URL     [本文引用: 1]

Zhou H J, Xue F, Chang H, et al.

Effect of Mo on microstructural characteristics and coarsening kinetics of γ' precipitates in Co-Al-W-Ta-Ti alloys

[J]. J. Mater. Sci. Technol., 2018, 34: 799

DOI      [本文引用: 1]

The solvus temperature, volume fraction, coarsening behavior of γ' precipitates and the partitioning behavior of alloying elements as well as lattice misfit of γ/γ' phases influence the creep behavior of Ni- and Co-base superalloys. However, few investigations about the microstructural characteristics and the coarsening behavior of γ' precipitates were reported in multicomponent novel Co-base superalloys during thermal exposure. Two alloys containing different contents of molybdenum and tungsten have been investigated to explore the effect of molybdenum on γ' solvus temperature, γ + γ' microstructure and γ' coarsening in Co-Al-W-Ta-Ti-base alloys. The results showed that the γ' solvus temperature decreases with the addition of Mo. Mo addition reduces the γ' volume fractions after aging above 1000 °C, but results in negligible influence on the γ' volume fractions aging at 900 °C. Meanwhile, γ' coarsening is controlled by diffusion in experimental alloys after aging at 900 °C and 1000 °C, and the kinetics of γ' growth in experimental alloys are consistent with the predictions of LSW theory.

Neumeier S, Rehman H U, Neuner J, et al.

Diffusion of solutes in fcc cobalt investigated by diffusion couples and first principles kinetic Monte Carlo

[J]. Acta Mater., 2016, 106: 304

DOI      URL     [本文引用: 3]

Lee C S. Precipitation-hardening characteristics of ternary cobalt-aluminum-X alloys [D]. Tucson: The University of Arizona, 1971

[本文引用: 1]

Pollock T M.

Alloy design for aircraft engines

[J]. Nat. Mater., 2016, 15: 809

DOI      PMID      [本文引用: 1]

Chen Y C, Wang C P, Ruan J J, et al.

Development of low-density γ/γ' Co-Al-Ta-based superalloys with high solvus temperature

[J]. Acta Mater., 2020, 188: 652

DOI      URL     [本文引用: 1]

Chen Y C, Wang C P, Ruan J J, et al.

High-strength Co-Al-V-base superalloys strengthened by γ'-Co3(Al, V) with high solvus temperature

[J]. Acta Mater., 2019, 170: 62

DOI      URL     [本文引用: 1]

Ruan J J, Liu X J, Yang S Y, et al.

Novel Co-Ti-V-base superalloys reinforced by L12-ordered γ' phase

[J]. Intermetallics, 2018, 92: 126

DOI      URL     [本文引用: 1]

Zenk C H, Volz N, Bezold A, et al.

The effect of alloying on the thermophysical and mechanical properties of Co-Ti-Cr-based superalloys

[A]. Superalloys 2020 [C]. Cham: Springer, 2020: 909

[本文引用: 1]

Forsik S A J, Polar Rosas A O, Wang T, et al.

High-temperature oxidation behavior of a novel Co-base superalloy

[J]. Metall. Mater. Trans., 2018, 49A: 4058

[本文引用: 1]

Volz N, Zenk C H, Cherukuri R, et al.

Thermophysical and mechanical properties of advanced single crystalline Co-base superalloys

[J]. Metall. Mater. Trans., 2018, 49A: 4099

[本文引用: 1]

Knop M, Mulvey P, Ismail F, et al.

A new polycrystalline Co-Ni superalloy

[J]. JOM, 2014, 66: 2495

DOI      URL     [本文引用: 1]

Titus M S, Eggeler Y M, Suzuki A, et al.

Creep-induced planar defects in L12-containing Co- and CoNi-base single-crystal superalloys

[J]. Acta Mater., 2015, 82: 530

DOI      URL     [本文引用: 4]

Bocchini P J, Sudbrack C K, Noebe R D, et al.

Temporal evolution of a model Co-Al-W superalloy aged at 650oC and 750oC

[J]. Acta Mater., 2018, 159: 197

DOI      URL    

Shinagawa K, Omori T, Oikawa K, et al.

Ductility enhancement by boron addition in Co-Al-W high-temperature alloys

[J]. Scr. Mater., 2009, 61: 612

DOI      URL     [本文引用: 1]

Xu Y T, Xia T D, Yan J Q, et al.

Effect of alloying elements on oxidation behavior of Co-Al-W alloys at high temperature

[J]. Chin. J. Nonferrous Met., 2010, 20: 2168

DOI      URL     [本文引用: 1]

徐仰涛, 夏天东, 闫健强 等.

合金元素对Co-Al-W合金高温氧化行为的影响

[J]. 中国有色金属学报, 2010, 20: 2168

[本文引用: 1]

Liu X J, Chen Y C, Lu Y, et al.

Present research situation and prospect of multi-scale design in novel Co-based superalloys: A review

[J]. Acta Metall. Sin., 2020, 56: 1

[本文引用: 1]

刘兴军, 陈悦超, 卢 勇 等.

新型钴基高温合金多尺度设计的研究现状与展望

[J]. 金属学报, 2020, 56: 1

[本文引用: 1]

Zhu L L, Wei C D, Qi H Y, et al.

Experimental investigation of phase equilibria in the Co-rich part of the Co-Al-X (X = W, Mo, Nb, Ni, Ta) ternary systems using diffusion multiples

[J]. J. Alloys Compd., 2017, 691: 110

DOI      URL     [本文引用: 1]

Cao B X, Kong H J, Ding Z Y, et al.

A novel L12-strengthened multicomponent Co-rich high-entropy alloy with both high γ'-solvus temperature and superior high-temperature strength

[J]. Scr. Mater., 2021, 199: 113826

DOI      URL    

Guan Y, Liu Y C, Ma Z Q, et al.

Investigation on γ' stability in CoNi-based superalloys during long-term aging at 900oC

[J]. J. Alloys Compd., 2020, 842: 155891

DOI      URL    

Shi L, Yu J J, Cui C Y, et al.

Microstructural stability and tensile properties of a Ti-containing single-crystal Co-Ni-Al-W-base alloy

[J]. Mater. Sci. Eng., 2015, A646: 45

Fan Z D, Wang X G, Yang Y H, et al.

Plastic deformation behaviors and mechanical properties of advanced single crystalline CoNi-base superalloys

[J]. Mater. Sci. Eng., 2019, A748: 267

Chen J, Guo M, Yang M, et al.

Double minimum creep processing and mechanism for γ' strengthened cobalt-based superalloy

[J]. J. Mater. Sci. Technol., 2022, 112: 123

DOI      [本文引用: 1]

The double minimum creep, characterized by two creep rate minima, in Co-based superalloy is investigated using a phase-field model coupled with a crystal plasticity model. The constitutive modeling, based on the dislocation slip theory considering dislocation interaction, is applied to simulate microstructural evolution and deformation behavior. Rafting process commences at the beginning of creep until the global minimum of creep rate is reached, demonstrating a strengthening effect from N-type rafts under compressive creep. The high shear strain rate of $\left( 111 \right)\left[ 0\bar{1}1 \right]$ slip system in the intersections of horizontal and vertical γ channels leads to a slight increase of creep rate after the first local minimum. The evolution of stress field shows that the softening effect is the combined effect of the increase of resolved shear stress and the decrease of hardening stress in the intersections. Further, these changes in stress are primarily caused by the dislocation annihilation and the inhomogeneous plastic deformation. This study indicates that the intermediate local softening stage during creep may be eliminated if the initial inter-distance between γʹ precipitates is decreased.

Zhu J, Titus M S, Pollock T M.

Experimental investigation and thermodynamic modeling of the Co-rich region in the Co-Al-Ni-W quaternary system

[J]. J. Phase Equilib. Diffus., 2014, 35: 595

DOI      URL     [本文引用: 1]

Chen T L, Guo C P, Li C R, et al.

Experimental investigation of the phase relations in the Al-Co-Ti system

[J]. J. Phase Equilib. Diffus., 2019, 40: 254

DOI      [本文引用: 1]

Zhou C Y, Guo C P, Li J B, et al.

Experimental investigations of the Co-Ni-Ti system: Liquidus surface projection and isothermal section at 1373 K

[J]. J. Alloys Compd., 2018, 754: 268

DOI      URL     [本文引用: 1]

Zhou C Y, Guo C P, Li C R, et al.

Investigation on the intermetallic compound Co3Ta and high-temperature phase equilibria in the Co-Ni-Ta system

[J]. Intermetallics, 2019, 108: 1

DOI      URL     [本文引用: 1]

Yang S Y. Thermodynamic analysis and alloy design of Co-Al-W based superalloys [D]. Shenyang: Northeastern University, 2012

[本文引用: 1]

杨舒宇. Co-Al-W基高温合金热力学分析及合金设计 [D]. 沈阳: 东北大学, 2012

[本文引用: 1]

Ruan J J, Xu W W, Yang T, et al.

Accelerated design of novel W-free high-strength Co-base superalloys with extremely wide γ/γ' region by machine learning and CALPHAD methods

[J]. Acta Mater., 2020, 186: 425

DOI      URL     [本文引用: 1]

Zhuang X L, Lu S, Li L F, et al.

Microstructures and properties of a novel γ'-strengthened multi-component CoNi-based wrought superalloy designed by CALPHAD method

[J]. Mater. Sci. Eng., 2020, A780: 139219

[本文引用: 1]

Jiang C.

First-principles study of Co3(Al, W) alloys using special quasi-random structures

[J]. Scr. Mater., 2008, 59: 1075

DOI      URL     [本文引用: 1]

Kobayashi S, Tsukamoto Y, Takasugi T, et al.

Determination of phase equilibria in the Co-rich Co-Al-W ternary system with a diffusion-couple technique

[J]. Intermetallics, 2009, 17: 1085

DOI      URL     [本文引用: 1]

Chen M, Wang C Y.

First-principle investigation of 3d transition metal elements in γ'-Co3(Al, W)

[J]. J. Appl. Phys., 2010, 107: 093705

[本文引用: 1]

Xu W W, Han J J, Wang Z W, et al.

Thermodynamic, structural and elastic properties of Co3 X (X = Ti, Ta, W, V, Al) compounds from first-principles calculations

[J]. Intermetallics, 2013, 32: 303

DOI      URL     [本文引用: 1]

Gao Q Z, Zhang X M, Ma Q S, et al.

Accelerating design of novel Cobalt-based superalloys based on first-principles calculations

[J]. J. Alloys Compd., 2022, 927: 167012

DOI      URL     [本文引用: 1]

Zhao J C, Zheng X, Cahill D G.

High-throughput diffusion multiples

[J]. Mater. Today, 2005, 8: 28

[本文引用: 1]

Suzuki A, Morra M M, Larsen M. Cobalt-nickel superalloys, and related articles [P]. US Pat, 20110268989A1, 2010

[本文引用: 1]

Li W D, Li L F, Antonov S, et al.

High-throughput exploration of alloying effects on the microstructural stability and properties of multi-component CoNi-base superalloys

[J]. J. Alloys Compd., 2021, 881: 160618

DOI      URL     [本文引用: 2]

Stewart C A, Suzuki A, Rhein R K, et al.

Oxidation behavior across composition space relevant to Co-based γ/γ' alloys

[J]. Metall. Mater. Trans., 2019, 50A: 5445

[本文引用: 1]

Fan L L, Li Y, Zhao X Y, et al.

High-throughput preparation and characterization of early hot-corrosion behaviors of compositional gradient Al-Cr complex coatings on a novel Co-Al-W-based alloy

[J]. Corros. Sci., 2021, 192: 109811

DOI      URL     [本文引用: 1]

Zhongguancun Material Testing Technology Alliance. T/CSTM 00120—2019 general rule for materials genome engineering data [S]. 2019

[本文引用: 1]

中关村材料试验技术联盟. T/CSTM 00120-2019 材料基因工程数据通则 [S]. 2019

[本文引用: 1]

Su Y J, Fu H D, Bai Y, et al.

Progress in materials genome engineering in China

[J]. Acta Metall. Sin., 2020, 56: 1313

[本文引用: 1]

宿彦京, 付华栋, 白 洋 等.

中国材料基因工程研究进展

[J]. 金属学报, 2020, 56: 1313

[本文引用: 1]

Liu P, Huang H Y, Antonov S, et al.

Machine learning assisted design of γ'-strengthened Co-base superalloys with multi-performance optimization

[J]. npj Comput. Mater., 2020, 6: 62

DOI      [本文引用: 1]

Designing a material with multiple desired properties is a great challenge, especially in a complex material system. Here, we propose a material design strategy to simultaneously optimize multiple targeted properties of multi-component Co-base superalloys via machine learning. The microstructural stability, γ′ solvus temperature, γ′ volume fraction, density, processing window, freezing range, and oxidation resistance were simultaneously optimized. A series of novel Co-base superalloys were successfully selected and experimentally synthesized from &gt;210,000 candidates. The best performer, Co-36Ni-12Al-2Ti-4Ta-1W-2Cr, possesses the highest γ′ solvus temperature of 1266.5 °C without the precipitation of any deleterious phases, a γ′ volume fraction of 74.5% after aging for 1000 h at 1000 °C, a density of 8.68 g cm−3 and good high-temperature oxidation resistance at 1000 °C due to the formation of a protective alumina layer. Our approach paves a new way to rapidly design multi-component materials with desired multi-performance functionality.

Lu S, Zou M, Zhang X R, et al.

Data-driven “cross-component” design and optimization of γ'-strengthened Co-based superalloys

[J]. Adv. Eng. Mater., 2023, 25: 2201257

DOI      URL     [本文引用: 1]

Yu J X, Wang C L, Chen Y C, et al.

Accelerated design of L12-strengthened Co-base superalloys based on machine learning of experimental data

[J]. Mater. Des., 2020, 195: 108996

DOI      URL     [本文引用: 1]

Lu S, Antonov S, Li L F, et al.

Two steady-state creep stages in Co-Al-W-base single-crystal superalloys at 1273 K/137 MPa

[J]. Met-all. Mater. Trans., 2018, 49A: 4079

[本文引用: 8]

Lu S, Antonov S, Li L F, et al.

Atomic structure and elemental segregation behavior of creep defects in a Co-Al-W-based single crystal superalloys under high temperature and low stress

[J]. Acta Mater., 2020, 190: 16

DOI      URL     [本文引用: 17]

Lu S, Luo Z E, Li L F, et al.

Comparison of creep mechanisms between Co-Al-W- and CoNi-based single crystal superalloys at low temperature and high stresses

[J]. Metall. Mater. Trans., 2023, 54A: 1597

[本文引用: 1]

Shi L, Yu J J, Cui C Y, et al.

The creep deformation behavior of a single-crystal Co-Al-W-base superalloy at 900oC

[J]. Mater. Sci. Eng., 2015, A635: 50

[本文引用: 3]

Lenz M, Eggeler Y M, Müller J, et al.

Tension/Compression asymmetry of a creep deformed single crystal Co-base superalloy

[J]. Acta Mater., 2019, 166: 597

DOI      URL     [本文引用: 7]

Tanaka K, Ooshima M, Tsuno N, et al.

Creep deformation of single crystals of new Co-Al-W-based alloys with fcc/L12 two-phase microstructures

[J]. Philos. Mag., 2012, 92: 4011

DOI      URL     [本文引用: 5]

Titus M S. High temperature deformation mechanisms of L12-containing Co-based superalloys [D]. Santa Barbara: University of California, 2015

[本文引用: 3]

Titus M S, Rettberg L H, Pollock T M.

High temperature creep of γ'-containing CoNi-based superalloys

[A]. Superalloys 2016 [C]. Hoboken: Wiley, 2016: 141

[本文引用: 1]

Zhou H J, Li L F, Antonov S, et al.

Sub/micro-structural evolution of a Co-Al-W-Ta-Ti single crystal superalloy during creep at 900oC and 420 MPa

[J]. Mater. Sci. Eng., 2020, A772: 138791

[本文引用: 3]

Tetzlaff U, Mughrabi H.

Enhancement of the high-temperature tensile creep strength of monocrystalline nickel-base superalloys by pre-rafting in compression

[A]. Superalloys 2000 [C]. Warrendale: TMS, 2000: 273

[本文引用: 1]

Chung D W, Ng D S, Dunand D C.

Influence of γ'-raft orientation on creep resistance of monocrystalline Co-based superalloys

[J]. Materialia, 2020, 12: 100678

DOI      URL     [本文引用: 1]

Rae C M F, Reed R C.

Primary creep in single crystal superalloys: Origins, mechanisms and effects

[J]. Acta Mater., 2007, 55: 1067

DOI      URL     [本文引用: 1]

Lenz M, Wu M J, He J Y, et al.

Atomic structure and chemical composition of planar fault structures in Co-base superalloys

[A]. Superalloys 2000 [C]. Cham: Springer, 2020: 920

[本文引用: 6]

Li Q J, Li J, Shan Z W, et al.

Strongly correlated breeding of high-speed dislocations

[J]. Acta Mater., 2016, 119: 229

DOI      URL     [本文引用: 1]

Lu S, Antonov S, Xue F, et al.

Segregation-assisted phase transformation and anti-phase boundary formation during creep of a γ'-strengthened Co-based superalloy at high temperatures

[J]. Acta Mater., 2021, 215: 117099

DOI      URL     [本文引用: 9]

Smith T M, Good B S, Gabb T P, et al.

Effect of stacking fault segregation and local phase transformations on creep strength in Ni-base superalloys

[J]. Acta Mater., 2019, 172: 55

DOI      [本文引用: 3]

In this study, two similar, commercial polycrystalline Ni-based disk superalloys (LSHR and ME3) were creep tested at 760 degrees C and 552 MPa to approximately 0.3% plastic strain. LSHR consistently displayed superior creep properties at this stress/temperature regime even though the microstructural characteristics between the two alloys were comparable. High resolution structural and chemical analysis, however, revealed significant differences between the two alloys among active gamma' shearing modes involving superlattice intrinsic and extrinsic stacking faults. In ME3, Co and Cr segregation and Ni and Al depletion were observed along the intrinsic faults-revealing a gamma' to gamma phase transformation. Conversely in LSHR, an alloy with a higher W content, Co and W segregation was observed along the intrinsic faults. This observation combined with scanning transmission electron microscopy (STEM) simulations confirm a gamma'-to-D0(19) chi phase transformation along the intrinsic faults in LSHR. Using experimental observations and density functional theory calculations, a novel local phase transformation strengthening mechanism is proposed that could be further utilized to improve the high temperature creep capabilities of Ni-base disk alloys. Published by Elsevier Ltd on behalf of Acta Materialia Inc.

Lilensten L, Kürnsteiner P, Mianroodi J R, et al.

Segregation of solutes at dislocations: A new alloy design parameter for advanced superalloys

[A]. Superalloys 2020 [C]. Cham: Springer, 2020: 41

[本文引用: 1]

Zhang Y, Li J S, Wang W Y, et al.

When a defect is a pathway to improve stability: A case study of the L12 Co3TM superlattice intrinsic stacking fault

[J]. J. Mater. Sci., 2019, 54: 13609

DOI      [本文引用: 6]

Effect of solutes of transition metals (TM = Cr, Fe, Hf, Mn, Mo, Nb, Ni, Pt, Rh, Ru, Re, Ta, Ti, V, W, Y and Zr) on the local phase transition between the L1(2) and D0(19) structures in superlattice intrinsic stacking fault (SISF) of Co3TM has been investigated. All the models employed herein, i.e. (1) the SISF-containing supercell, (2) the axial nearest-neighbor Ising (ANNI) model, and (3) both the L1(2)- and D0(19)-containing (L1(2) + D0(19)) supercell, yield the same result regarding the stability of SISF in L1(2)-type Co3TM. In the view of bonding charge density, the atomic and electronic basis of local D0(19) phase transition in the SISF fault layers of Co3TM are revealed. Especially, the negative SISF energy predicted by the L1(2) + D0(19) model suggests that both the SISF fault layers (i.e. the local D0(19) structure) and the L12 phase of Co3TM can be stabilized through a coupling interaction between the fault layers and the solutes, paving a pathway to stabilize Co-base superalloys via Co3TM precipitate. Moreover, the consist results of E-SISF via the ANNI model with the classical SISF-supercell method utilized in first-principles calculations supports the approach to efficiently distinguish various planar faults and predict their corresponding energies, such as SISF, superlattice intrinsic stacking fault, anti-phase boundaries, and so on.

Wang W Y, Xue F, Zhang Y, et al.

Atomic and electronic basis for solutes strengthened (010) anti-phase boundary of L12 Co3(Al, TM): A comprehensive first-principles study

[J]. Acta Mater., 2018, 145: 30

DOI      URL     [本文引用: 6]

Titus M S, Mottura A, Babu Viswanathan G, et al.

High resolution energy dispersive spectroscopy mapping of planar defects in L12-containing Co-base superalloys

[J]. Acta Mater., 2015, 89: 423

DOI      URL     [本文引用: 2]

Titus M S, Rhein R K, Wells P B, et al.

Solute segregation and deviation from bulk thermodynamics at nanoscale crystalline defects

[J]. Sci. Adv., 2016, 2: e1601796

DOI      URL     [本文引用: 3]

Atomistic processes governing the high-temperature strength of structural materials were accurately characterized and modeled.

Barba D, Smith T M, Miao J, et al.

Segregation-assisted plasticity in Ni-based superalloys

[J]. Metall. Mater. Trans., 2018, 49A: 4173

[本文引用: 4]

Makineni S K, Kumar A, Lenz M, et al.

On the diffusive phase transformation mechanism assisted by extended dislocations during creep of a single crystal CoNi-based superalloy

[J]. Acta Mater., 2018, 155: 362

DOI      URL     [本文引用: 2]

He J Y, Zenk C H, Zhou X Y, et al.

On the atomic solute diffusional mechanisms during compressive creep deformation of a Co-Al-W-Ta single crystal superalloy

[J]. Acta Mater., 2020, 184: 86

DOI      URL     [本文引用: 1]

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