Effect of heat treatment on microstructure and hardness of novel Ni-Co based superalloys

doi:10.13251/j.issn.0254-6051.2023.05.031

Abstract

Abstract: Three novel Ni-Co based superalloys with different (W+Ta) contents were designed by using CALPHAD method, and solution and aging treatment of the alloys were determined by the equilibrium phase diagram. The microstructural characteristics of the Ni-Co based superalloys after heat treatment were analysed by means of OM, SEM and EDS. The results show that the as-cast microstructure of the three Ni-Co based superalloys is composed of γ phase, γ′ phase, γ+γ′ eutectic structure and carbides, and the γ+γ′ eutectic structure is radial. After solution treatment, the as-cast primary γ′ phase is completely eliminated, and tertiary γ′ phases are precipitated after aging at 800 ℃. With the increase of aging time, the size of γ′ phase increases, and the hardness of the alloys also increases, however, the precipitated γ′ phases in the alloy with high W+Ta content aged at 800 ℃ are split, that results in hardness increasing first and then decreasing.

Key words: Ni-Co based superalloys, heat treatment, microstructure, γ′ phase splitting, hardness

CLC Number:

TG156.1

Hu Jiahao, Gao Jiali, Zhang Shangzhou. Effect of heat treatment on microstructure and hardness of novel Ni-Co based superalloys[J]. Heat Treatment of Metals, 2023, 48(5): 204-209.

References

[1]Reed R C. The Superalloys Fundamentals and Applications[M]. Cambridge: Cambridge University Press, 2006.
[2]杜金辉, 吕旭东, 董建新, 等. 国内变形高温合金研制进展[J]. 金属学报, 2019, 55(9): 1115-1132.
Du Jinhui, Lü Xudong, Dong Jianxin, et al. Research progress of wrought superalloys in China[J]. Acta Metallurgica Sinica, 2019, 55(9): 1115-1132.
[3]唐中杰, 郭铁明, 付迎, 等. 镍基高温合金的研究现状与发展前景[J]. 金属世界, 2014(1): 36-40.
Tang Zhongjie, Guo Tieming, Fu Ying, et al. Research present situation and the development prospect of nickel-based superalloy[J]. Metal World, 2014(1): 36-40.
[4]Yuan Y, Gu Y F, Osada T, et al. A new method to strengthen turbine disc superalloys at service temperatures[J]. Scripta Materialia, 2012, 66(11): 884-889.
[5]Wang B, Zhang J, Huang T W, et al. Effect of Co on microstructural stability of the third generation Ni-based single crystal superalloys[J]. Journal of Materials Research volume, 2016, 31(9): 1328-1337.
[6]Gu Y F, Fukuda T, Cui C, et al. Comparison of mechanical properties of TMW alloys, new generation of cast-and-wrought superalloys for disk applications[J]. Metallurgical and Materials Transactions A, 2009, 40(13): 3047-3050.
[7]Yu X, Yu Z C, Zhang L N, et al. Understanding the composition-dependent stability of η phase for future Ni-Co-based superalloys[J]. Scripta Materialia, 2022, 219: 114886.
[8]谷月峰, 崔传勇, 袁勇, 等. 一种高性能航空涡轮盘用铸锻合金的研究进展[J]. 金属学报, 2015, 51(10): 1191-1206.
Gu Yuefeng, Cui Chuanyong, Yuan Yong, et al. Research progress in a high-performance cast wrought superalloy for turbine disc applications[J]. Acta Metallurgica Sinica, 2015, 51(10): 1191-1206.
[9]Shi Q, Ding X, Wang M, et al. Co effect on as-cast and heat-treated microstructures in Ru-containing single-crystal superalloys[J]. Metallurgical and Materials Transactions A, 2014, 45: 1833-1843.
[10]Yuan Y, Gu Y F, Zhong Z H, et al. Enhanced strength at intermediate temperatures in a Ni-base disk superalloy with high Co addition[J]. Materials Science and Engineering A, 2012, 556(30): 595-600.
[11]Xu Y, Lei Z, Li J, et al. Relationship between Ti/Al ratio and stress-rupture properties in nickel-based superalloy[J]. Materials Science and Engineering A, 2012, 544(15): 48-53.
[12]Bai J M, Xing P Y, Zhang H P, et al. Effect of tantalum on the microstructure stability of PM Ni-base superalloys[J]. Materials Characterization, 2021, 179: 111326.
[13]陈国良. 高温合金学[M]. 北京: 冶金工业出版社, 1988.
[14]Bai J M, Zhang H P, Liu J T, et al. Investigation of room temperature strengthening mechanism on PM Ni-base superalloys with tantalum addition[J]. Materials Characterization, 2022, 191: 112089.
[15]朱耀宵, 徐乐英, 赵洪恩, 等. 一种铸造镍基高温合金中(γ+γ′)共晶的形成及σ相的控制[J]. 金属学报, 1986, 22(2): 5-12.
Zhu Yaoxiao, Xu Leying, Zhao Hongen, et al. Formation of (γ+γ′) eutectic and control of σ-phase in a high Al-Ti cast Ni-base superalloy[J]. Acta Metallurgica Sinica, 1986, 22(2): 5-12.
[16]Heckl A, Rettig R, Cenanovic R, et al. Investigation of the final stages of solidification and eutectic phase formation in Re and Ru containing nickel-base superalloys[J]. Journal of Crystal Growth, 2010, 312(14): 2137-2144.
[17]Masoumi F, Jahazi M, Shahriari D, et al. Coarsening and dissolution of γ′ precipitates during solution treatment of AD730 Ni-based superalloy: Mechanisms and kinetics models[J]. Journal of Alloys and Compounds, 2016, 658: 981-995.
[18]Roy I, Balikci E, Ibekwe S, et al. Precipitate growth activation energy requirements in the duplex size γ′ distribution in the superalloy IN738LC[J]. Journal of Materials Science, 2005, 40(23): 6207-6215.
[19]Doi M, Miyazaki T, Wakatsuki T. The effect of elastic interaction energy on the morphology of γ′ precipitates in nickel-based alloys[J]. Materials Science and Engineering, 1984, 67(2): 247-253.
[20]Qiu Y Y. The splitting behavior of γ′ particles in Ni-based alloys[J]. Journal of Alloys and Compounds, 1998, 270(1): 145-153.
[21]Banerjee D, Banerjee R. Formation of split patterns of γ′ precipitates in Ni-Al via particle aggregation[J]. Scripta Materialia, 1999, 41(9): 1023-1030.