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金属学报  2018, Vol. 54 Issue (5): 615-626    DOI: 10.11900/0412.1961.2018.00075
  金属材料的凝固专刊 本期目录 | 过刊浏览 |
高梯度定向凝固技术及其在高温合金制备中的应用
刘林(), 孙德建, 黄太文, 张琰斌, 李亚峰, 张军, 傅恒志
西北工业大学凝固技术国家重点实验室 西安 710072
Directional Solidification Under High Thermal Gradient and Its Application in Superalloys Processing
Lin LIU(), Dejian SUN, Taiwen HUANG, Yanbin ZHANG, Yafeng LI, Jun ZHANG, Hengzhi FU
State Key Laborotory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China
引用本文:

刘林, 孙德建, 黄太文, 张琰斌, 李亚峰, 张军, 傅恒志. 高梯度定向凝固技术及其在高温合金制备中的应用[J]. 金属学报, 2018, 54(5): 615-626.
Lin LIU, Dejian SUN, Taiwen HUANG, Yanbin ZHANG, Yafeng LI, Jun ZHANG, Hengzhi FU. Directional Solidification Under High Thermal Gradient and Its Application in Superalloys Processing[J]. Acta Metall Sin, 2018, 54(5): 615-626.

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摘要: 

工业燃机用大型复杂定向或单晶叶片制备的需求,对传统的高速凝固(HRS)定向凝固技术提出了挑战,以液态金属冷却法(LMC)为代表的高梯度定向凝固技术迎来了发展机遇。本文总结分析了高梯度定向凝固技术的工作原理、所制备铸件的组织特点、以及其对凝固缺陷、固溶热处理、力学性能的影响。高梯度定向凝固技术提高了铸件内的温度梯度和冷却速率,因而能够显著减小一次及二次枝晶间距、碳化物、共晶和铸态孔洞尺寸,降低了共晶和铸态孔洞的含量;并降低了热处理过程中固溶孔的含量和元素的残余偏析;该技术还有效抑制雀斑缺陷,提高杂晶形成的临界抽拉速率,减小晶粒取向偏离。高梯度定向凝固技术能够显著提高高温合金的持久性能,但对于单晶合金在高温下提高幅度较小,低周与高周疲劳性能均明显提高,且降低了数据分散度,但在氧化条件下改善幅度减小。

关键词 液态金属冷却定向凝固温度梯度高温合金力学性能    
Abstract

Industrial gas turbines (IGTs) are the key equipment to achieving energy strategy, such as energy conservation and clean power generation. When the large and complex IGT blades are fabricated by the conventional Bridgman directional solidification process, the thermal gradients at the solidification front are low and unstable, resulting in some disadvantages: the coarse dendrite structure with severe dendritic segregation, the increased occurrence of casting defects and the poor performance of mechanical properties. These disadvantages provide a good opportunity for rapid development of the directional solidification with high thermal gradient (HG), such as the liquid metal cooling (LMC). In the present work, the physical basis of HG process, the microstructure, mechanical properties, solution heat treatment, and casting defects of the superalloys processed by HG process, have been reviewed. The HG process increases the thermal gradient and the cooling rate, thus permitting microstructural improvements including a more homogeneous fine-dendrite structure with lower elemental segregation and shrinkage porosity, and refinement of carbide, γ′ phase and eutectic, reducing the volume fraction of eutectic and shrinkage porosity. During the solution heat treatment, the HG process increases the incipient melting temperature and reduces the residual segregation as well as the content of solution pore. The HG process could effectively inhibit the formation of freckle chains, increase the critical withdrawal rate of the stray grain formation, and decrease the degree of the misorientation of the <001> grain orientation from the casting axis. Moreover, the HG process could improve the mechanical properties including the stress rupture life, low-cycle fatigue (LCF), high-cycle fatigue properties and short-term strength, but the improvement might be reduced at higher temperature or under the oxidation condition.

Key wordsliquid metal cooling    directional solidification    thermal gradient    superalloy    mechanical property
收稿日期: 2018-02-28     
ZTFLH:  TG21  
基金资助:资助项目 国家自然科学基金项目Nos.51331005、51631008、51690163和51771148,国家重点研发计划项目Nos.2016YFB0701400和2017YFB0702900
作者简介:

作者简介 刘 林,男,1956年生,教授

Technology Location PDAS / mm G / (Kcm-1) Cooling media
Shoulder Airfoil
HRS 0.60 0.55 20~40 -
LMC






Germany ENUa 0.30 0.25 50~60 Sn
DPCb 0.38 0.36 40~50 Sn
USA
MUc 0.39 0.28 60~80 Sn
GEd 0.26 0.22 - Sn
GEd - 0.20 40~65 Al
Russia VIAMe - - ~120 Al
China IMRf 0.35 0.30 80~100 Sn
NWPUg 0.26 0.22 170~250 Ga-In-Sn
表1  国内外定向凝固设备特征参量的比较
图1  不同温度梯度(G)和抽拉速率(V)下的枝晶形貌[19,35]
G / (Kcm-1) Al Cr Mo W Ta Re
60 0.7 1.2 1.2 2.1 0.5 3.4
200 0.8 1 0.9 1.5 0.6 2.5
表2  ZhS-47合金(9%Re,质量分数)在不同温度梯度下定向凝固的偏析系数[7]
图2  HRS与LMC工艺下的碳化物形貌[37]
图3  G对铸态孔体积分数(Q)的影响[40]
图4  G对铸态γ′?相尺寸(d)的影响[40]
图5  DD33合金的凝固组织与固溶热处理组织的元素偏析
图6  定向凝固参数和零件尺寸与雀斑形成区域的关系[8]
图7  HRS和LMC制备的涡轮叶片缘板杂晶出现情况的实验和模拟结果[53]
图8  棒状铸件和叶片的取向图[10]
Defect Conventional (HRS) High-gradient (LMC) Location
Freckle chain 4 1 Root
High angle boundary 3 2 Leading-edge platform, trailing edge, root
Recrystallized grain 1 4 Concave platform edge, leading edge
Zebra grain 0 1 Leading-edge platform
表3  Titan 130发动机一级叶片的铸造缺陷[10]
图9  在低梯度(LG)和高梯度(HG)定向凝固Mar-M246合金的蠕变曲线[59,60]
Technology G
Kcm-1
V
mmmin-1
Rupture life
h
Elongation
%
HRS 50 5 69.93 25.0
LMC 218 3 100.90 20.9
LMC 218 7 96.22 29.7
LMC 218 10 91.15 31.2
表4  HRS与LMC工艺条件下DZ125合金的持久寿命[61]
Test condition Rupture life / h
Temperature / ℃ Stress / MPa HG LG
760 750 1138 759
850 500 359 -
900 380 230 212
950 240 386 341
1000 200 177 162
1050 120 1055 -
1050 140 288 255
表5  在LG和HG定向凝固CMSX-2合金的持久寿命[62]
Technology Dendrite arm spacing
μm
Rupture life / h Elongation / %
As cast After heat treatment As cast After heat treatment
HRS 350 39.4 84.0 25.2 22.0
HRS 245 52.6 67.0 31.3 39.0
LMC 123 58.6 64.0 34.7 32.5
LMC 79 64.8 108.8 38.1 24.0
LMC 38 76.4 131.5 34.1 35.1
表6  HRS与LMC工艺条件下的持久寿命[19,35]
图10  HRS与LMC工艺下的蠕变性能[32]
图11  GTD444合金的低周疲劳寿命比较[26]
图12  HRS与LMC工艺在950 ℃时的低周疲劳性能[32]
图13  CMSX-2合金的高周疲劳寿命比较[62]
图14  PWA1483合金的高周疲劳寿命比较[31]
G / (Kcm-1) Short-term strength at 20 ℃ / MPa Rupture life under 1100 ℃ and 120 MPa / h
20 87 57
100 107 118
200 120 139
表7  温度梯度对力学性能的影响[40]
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