Please wait a minute...
Acta Metall Sin  2015, Vol. 51 Issue (1): 67-76    DOI: 10.11900/0412.1961.2014.00281
Current Issue | Archive | Adv Search |
EFFECTS OF (W+Mo)/Cr RATIO ON MICROSTRUC-TURAL EVOLUTIONS AND MECHANICAL PROPER-TIES OF CAST Ni-BASED SUPERALLOYS DURING LONG-TERM THERMAL EXPOSURE
SUN Wen1, 2, QIN Xuezhi2, GUO Jianting2, LOU Langhong2, ZHOU Lanzhang2
1 University of Science and Technology of China, Hefei 230022; 2 Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016
Download:  HTML  PDF(18347KB) 
Export:  BibTeX | EndNote (RIS)      
Abstract  The Ni-based superalloys are widely used as microstructural components of modern turbine engines due to its good high temperature strength, good fatigue and creep property and excellent hot-corrosion resistance. In order to increase their high temperature strength, more and more refractory elements, such as W and Mo, are added into these alloys while Cr content gradually decreases. During long-term aging, these alloys generally experience various microstructural changes, including coarsening of g' phase coarsening, formation of a continuous grain boundary (GB) carbide network, precipitation topologically close-packed (TCP) phase, and degeneration of MC carbide. However, there is limited available data about the effect of (W+Mo)/Cr ratios on the microstructural evolution of Ni-based superalloys. In this work, the cast Ni-based superalloys with different (W+Mo)/Cr ratios (mass ratios) are fabricated by vacuum induction furnace. After standard heat treated (1110 ℃, 4.5 h, air cooling+750 ℃, 10.5 h, air cooling), they are thermally exposed at 850 ℃ for different times. The stress-rupture tests are operated under the condition of 800 ℃, 294 MPa. Effects of (W+Mo)/Cr ratios on the microstructure evolutions and mechanical properties are investigated by the combination of OM, SEM, TEM and stress-rupture tests. The experiment results show that the (W+Mo)/Cr ratio has no obvious influence on the standard heat treated microstructure, which is mainly composed of g matrix, g' phase, MC carbide and secondary carbides distributing at grain boundaries. During long-term thermal exposure, the microstructure evolutions occur by g' phase coarsening, TCP phases formation, MC degeneration and grain boundary coarsening. The g' phase coarsening behavior is not affected obviously by the (W+Mo)/Cr ratio. However, the amount of TCP phases decreases significantly with decreasing of (W+Mo)/Cr ratio and the type of TCP phases transforms from m phase to coexist of m and s phases when (W+Mo)/Cr ratio decreases from 0.55 to 0.37. There are no TCP phases observed in the sample with (W+Mo)/Cr ratio of 0.22. The thermal stability of MC carbide is reduced obviously and the grain boundaries coarsen more severely by the decrease of (W+Mo)/Cr ratio. The degradation of stress-rupture property is attributed to the coarsening of g' phase and grain boundaries and the formation of TCP phases. Combined with the effect of (W+Mo)/Cr ratio on the solid solution strengthening, microstructure evolution and stress-rupture property, it can be concluded that the optimum stress-rupture property can be obtained when the (W+Mo)/Cr ratio is about 0.37.
Key words:  Ni-based superalloy      (W+Mo)/Cr ratio      long-term aging      microstructural evolution      mechanical property     
ZTFLH:  TA211.8  
Fund: ; Supported by National Natural Science Foundation of China (No.51001101) and High Technology Research and Development Program of China (No.2012AA03A501)
Corresponding Authors:  Correspondent: QIN Xuezhi, associate professor, Tel: (024)83978469, E-mail: xzqin@imr.ac.cn     E-mail:  xzqin@imr.ac.cn

Cite this article: 

SUN Wen, QIN Xuezhi, GUO Jianting, LOU Langhong, ZHOU Lanzhang. EFFECTS OF (W+Mo)/Cr RATIO ON MICROSTRUC-TURAL EVOLUTIONS AND MECHANICAL PROPER-TIES OF CAST Ni-BASED SUPERALLOYS DURING LONG-TERM THERMAL EXPOSURE. Acta Metall Sin, 2015, 51(1): 67-76.

URL: 

https://www.ams.org.cn/EN/10.11900/0412.1961.2014.00281     OR     https://www.ams.org.cn/EN/Y2015/V51/I1/67

Fig.1  

Typical microstructures of sample A1 after heat treatment

(a) OM image
(b) SEM image of g' phase
(c) SEM image of grain boundary

Fig.2  

SEM images of g' phase in different alloy samples after aged at 850 ℃ for different times

Fig.3  

Microstructures of A1 (a), A2 (b), A3 (c) and A4 (d) after aged at 850 ℃ for 0.5×103 h (The insets corresponds to the TEM images and SAED patterns)

Fig.4  

Microstructures of A1 (a), A2 (b), A3 (c) and A4 (d) after aged at 850 ℃ for 1×104 h

Fig.5  

Morphologies of MC degeneration after thermal exposure at 850 ℃ for 1×103 h in A1 (a), A2 (b), A3 (c) and A4 (d)

Fig.6  

Morphologies of MC degeneration after thermal exposure at 850 ℃ for 1×104 h in A1 (a), A2 (b), A3 (c) and A4 (d)

Fig.7  

Degeneration degree (D) of primary MC changes with aging time t

Fig.8  

Morphologies of grain boundaries after thermal exposure at 850 ℃ for 1×104 h in A1 (a), A2 (b), A3 (c) and A4 (d)

Fig.9  

Effect of (W+Mo)/Cr ratio on stress-rupture life of alloys after different exposure time

Fig.10  

Cross section microstructures of samples A1 (a), A2 (b), A3 (c) and A4 (d) after thermal exposure at 850 ℃ for 1×104 h under stress-rupture test at 800 ℃, 294 MPa (GB—grain boundary)

Table 1  

Chemical compositions of Ni-based superalloys

Table 2  

Compositions and thermal stability parameters of MC in alloys

[1] Guo J T. Materials Science and Engineering for Superalloys. Vol.1, Beijing: Science Press, 2008: 39 (郭建亭. 高温合金材料学(上册). 北京: 科学出版社, 2008: 39)
[2] Cai Y L, Zheng Y R. Acta Metall Sin, 1982; 18: 30 (蔡榆林, 郑运荣. 金属学报, 1982; 18: 30)
[3] Ross E W, Sims C T. In: Sims C T, Stoloff N S, Hagel W C eds., Superalloys II, New York: Wiley, 1987: 97
[4] Pollock T M. Mater Sci Eng, 1999; B32: 255
[5] Giamei A F, Anton D L. Metall Trans, 1985; 16A: 1997
[6] Rae C M F, Karunaratne M S A, Small C J, Broomfiels C N, Jones C N, Reed R C. In: Pollock T M, Kissinger R D, Bowman R R, Green K A, Mclean M, Olson S, Schirra J J eds., Superalloys 2000, Warrendale: TMS, 2000: 767
[7] Koul A K, Castillo R. Metall Trans, 1988; 19A: 2049
[8] Qin X Z, Guo J T, Yuan C, Chen C L, Ye H Q. Metall Mater Trans, 2007; 38A: 3014
[9] Qin X Z, Guo J T, Yuan C, Hou J S, Ye H Q. Mater Lett, 2008; 62: 258
[10] Qin X Z, Guo J T, Yuan C, Hou J S, Ye H Q. Mater Lett, 2008; 62: 2275
[11] Qin X Z, Guo J T, Yuan C, Yang G X, Zhou L Z, Ye H Q. J Mater Sci, 2009; 44: 4840
[12] Stevens R A, Flewitt P E J. Mater Sci Eng, 1979; A37: 237
[13] Lifshitz I M, Slyozov V V. J Phys Chem Solids, 1961; 19: 35
[14] Wanger C Z. Elektrochem, 1961; 65: 581
[15] Swalin R A, Martin A. J Met, 1956; 206: 567
[16] Van Der Molten F H, Oblak J M, Kriege O H. Metall Trans, 1971; 2: 1627
[17] Lvov G, Levit V I, Kaufman M J. Metall Mater Trans, 2004; 35A: 1669
[18] Wang J, Zhou L Z, Qin X Z, Sheng L Y, Hou J S, Guo J T. Mater Sci Eng, 2012; A533: 14
[19] Qin X Z, Guo J T, Yuan C, Yang G X, Zhou L Z, Ye H Q. Mater Sci Eng, 2008; A485: 74
[20] Sun W, Qin X Z, Guo Y A, Guo J T, Zhou L Z, Lou L H. Acta Metall Sin, 2014; 50: 744 (孙 文, 秦学智, 郭永安, 郭建亭, 周兰章, 楼琅洪.金属学报, 2014; 50: 744)
[21] Liu L R, Jin T, Zhao N R, Sun X F, Guan H R, Hu Z Q. Mater Sci Eng, 2003; A361:191
[22] Chen Q Z, Knowles D M. Metall Trans, 2002; 33A: 1319
[23] Pessah M, Caron P, Khan T. In: Antolovich S D, Stusrud R W, MacKay R A, Anton D L, Khan T, Kissinger R D, Klarstrom D L eds., Superalloys 1992, Warrendale: TMS, 1992,567
[24] Pessah-Simonetti M, Caron P, Khan T. Mater Sci Eng, 1998; A254: 1
[1] HUANG Yuan, DU Jinlong, WANG Zumin. Progress in Research on the Alloying of Binary Immiscible Metals[J]. 金属学报, 2020, 56(6): 801-820.
[2] GENG Yaoxiang, FAN Shimin, JIAN Jianglin, XU Shu, ZHANG Zhijie, JU Hongbo, YU Lihua, XU Junhua. Mechanical Properties of AlSiMg Alloy Specifically Designed for Selective Laser Melting[J]. 金属学报, 2020, 56(6): 821-830.
[3] ZHAO Yanchun, MAO Xuejing, LI Wensheng, SUN Hao, LI Chunling, ZHAO Pengbiao, KOU Shengzhong, Liaw Peter K.. Microstructure and Corrosion Behavior of Fe-15Mn-5Si-14Cr-0.2C Amorphous Steel[J]. 金属学报, 2020, 56(5): 715-722.
[4] YAO Xiaofei, WEI Jingpeng, LV Yukun, LI Tianye. Precipitation σ Phase Evoluation and Mechanical Properties of (CoCrFeMnNi)97.02Mo2.98 High Entropy Alloy[J]. 金属学报, 2020, 56(5): 769-775.
[5] LIANG Mengchao, CHEN Liang, ZHAO Guoqun. Effects of Artificial Ageing on Mechanical Properties and Precipitation of 2A12 Al Sheet[J]. 金属学报, 2020, 56(5): 736-744.
[6] LI Yuancai, JIANG Wugui, ZHOU Yu. Effect of Temperature on Mechanical Propertiesof Carbon Nanotubes-Reinforced Nickel Nano-Honeycombs[J]. 金属学报, 2020, 56(5): 785-794.
[7] JIANG Yi,CHENG Manlang,JIANG Haihong,ZHOU Qinglong,JIANG Meixue,JIANG Laizhu,JIANG Yiming. Microstructure and Properties of 08Cr19Mn6Ni3Cu2N (QN1803) High Strength Nitrogen Alloyed LowNickel Austenitic Stainless Steel[J]. 金属学报, 2020, 56(4): 642-652.
[8] YANG Ke,SHI Xianbo,YAN Wei,ZENG Yunpeng,SHAN Yiyin,REN Yi. Novel Cu-Bearing Pipeline Steels: A New Strategy to Improve Resistance to Microbiologically Influenced Corrosion for Pipeline Steels[J]. 金属学报, 2020, 56(4): 385-399.
[9] CAO Yuhan,WANG Lilin,WU Qingfeng,HE Feng,ZHANG Zhongming,WANG Zhijun. Partially Recrystallized Structure and Mechanical Properties of CoCrFeNiMo0.2 High-Entropy Alloy[J]. 金属学报, 2020, 56(3): 333-339.
[10] YU Lei,LUO Haiwen. Effect of Partial Recrystallization Annealing on Magnetic Properties and Mechanical Properties of Non-Oriented Silicon Steel[J]. 金属学报, 2020, 56(3): 291-300.
[11] ZHOU Xia,LIU Xiaoxia. Mechanical Properties and Strengthening Mechanism of Graphene Nanoplatelets Reinforced Magnesium Matrix Composites[J]. 金属学报, 2020, 56(2): 240-248.
[12] CHENG Chao,CHEN Zhiyong,QIN Xushan,LIU Jianrong,WANG Qingjiang. Microstructure, Texture and Mechanical Property ofTA32 Titanium Alloy Thick Plate[J]. 金属学报, 2020, 56(2): 193-202.
[13] WU Jing,LIU Yongchang,LI Chong,WU Yuting,XIA Xingchuan,LI Huijun. Recent Progress of Microstructure Evolution and Performance of Multiphase Ni3Al-Based Intermetallic Alloy with High Fe and Cr Contents[J]. 金属学报, 2020, 56(1): 21-35.
[14] ZHANG Jian,WANG Li,WANG Dong,XIE Guang,LU Yuzhang,SHEN Jian,LOU Langhong. Recent Progress in Research and Development of Nickel-Based Single Crystal Superalloys[J]. 金属学报, 2019, 55(9): 1077-1094.
[15] ZHANG Beijiang,HUANG Shuo,ZHANG Wenyun,TIAN Qiang,CHEN Shifu. Recent Development of Nickel-Based Disc Alloys andCorresponding Cast-Wrought Processing Techniques[J]. 金属学报, 2019, 55(9): 1095-1114.
No Suggested Reading articles found!