Compositional effect on TCP phase formation in Ru-containing Ni-based single crystal superalloys

Qianying Shi,Qiang Feng,Jie Li,Xianfei Ding,Lamei Cao,Jiajie Huo,Yunrong Zheng,J.Y Guédou,J Choné

doi:10.1051/matecconf/20141401002

Abstract

Microstructural instability involving the formation of topologically close-packed (TCP) phases is restricted during the alloy development of Ni-based single crystal superalloys. In this study, the effects of alloying elements including Co, Cr, Mo and Ru on the formation of different TCP phases were investigated in a series of single crystal superalloys. Experimental results showed that more additions of Cr and Mo promoted the TCP phase formation, while Co and Ru played a positive role in improving microstructural stability. It is indicated that σ, P and R phases existed with various morphology and compositions in different experimental alloys during thermal exposure at 1100 ∘ C. The content of Co, Cr and Mo in those alloys affected the types of TCP phases significantly, while Ru additions showed a negligible effect. R phase was prone to form in alloys containing high level of Co addition. Meanwhile, the ratio of Cr and Mo content had strong influence on the formation of σ and P phases in alloys containing low level of Co addition. The effects of alloying additions on the elemental partitioning ratios between γ and γ ′ phases contributed to their corresponding influence on TCP phase formation.

Highlights

Ni-based single crystal superalloys with superior mechanical properties at high temperature are widely used for turbine blades in aircraft engines
Microstructural instability involving the formation of topologically close packed (TCP) phases was investigated in a series of single crystal superalloys containing different levels of contents: low and high (Co), Cr, Mo and Ru additions in this study
The following conclusions can be drawn: (1) TCP phases existed with various morphologies and compositions in different experimental alloys during the thermal exposure at 1100 ◦C

Summary

Introduction

Ni-based single crystal superalloys with superior mechanical properties at high temperature are widely used for turbine blades in aircraft engines. It is worthy to evaluate the effects of Cr and Mo additions and maximize their capacity to increase the creep resistance. This will provide the possibility to decrease the level of Re additions, which increases the density and cost of advanced single crystal superalloys and limits their practical application. Since Co was considered to be a potential microstructural stabilizer in previous studies [8, 17, 18], the role of Co additions in advanced single crystal superalloys should be assessed to investigate whether it is applicable to add more Co as a substitute for a part of expensive Ru to achieve acceptable alloy stability

Results

Discussion

Conclusion