Microstructure and High Temperature Stress Rupture Properties of Ru-Containing Directionally Solidified Ni-Base Superalloy

Abstract:

In this investigation, 3wt.% Ru was added to a low Cr and high W content superalloy with a nominal composition of Ni-10Co-1.5Cr-2.0Mo-1.0Nb-5.5Al-1.2Ti-0.1C-0.02B (wt.%) and both the Ru-free and the Ru-bearing alloys were directionally solidified. The multi-step heat treatment, thermal exposure and stress rupture test were performed. The results indicate that Ru is a weak positive segregation element (k’=Cinterdendrite / Cdendrite= 1.03). The solubility of Ru in γ phase is 30% higher than that of in γ' phase. Ru hardly enters into MC carbides, but can effectively retard the formation of M6C carbides. Ruthenium reduces the amount of eutectic (γ+γ'), decreases solid solution temperature of γ' phase, and promotes the rafting tendency of γ/γ' at elevated temperatures. Ru-bearing alloy possesses rather higher life at 1100°C/118MPa due to decrease of the film-like M6C carbides. The addition of Ru can inhibit the formation of M6C and eutectic γ', which hinder the initiation and propagation of cracks.

• Periodical: Key Engineering Materials (Volumes 353-358)
• Pages: 507-510
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.353-358.507
• Online since: September 2007
• Authors: Liang Zheng, Shu Suo Li, Cheng Bo Xiao, Ding Zhong Tang, Chen Qing Gu
• Keywords: DS Superalloy, Microstructure, Ruthenium, Stress-Rupture Properties

References

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[2] A.C. Yeh et al.: Superalloys 2004, edited by A. Green et al., TMS, PA (2004), p.677.

[3] L. Zheng, C.Q. Gu and Y.R. Zheng: Scripta Materialia Vol. 50 (2004), p.435.

[4] L.J. Rowland et al.: Superalloys 2004, edited by A. Green et al., TMS, PA (2004), p.697.

[5] Liang Zheng: Scripta Materialia Vol. 53 (2005), p.943 Fig. 4. Microstructure of stress ruptured DS samples: (a) Alloy 1, 35. 6h; (b) Alloy 2, 44. 4h.