Different Effect of Co on the Formation of Topologically Close-Packed Phases in Ni-Cr-Mo and Ni-Cr-Re Alloys

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2017-11, Vol.48 (11), p.5639-5648
• Main Authors: Shi, Qianying, An, Ning, Huo, Jiajie, Ding, Xianfei, Zheng, Yunrong, Feng, Qiang
• Format: Article
• Language: English
• Subjects: Alloy systems; Alloying additive; Aluminum alloys; Cellular precipitates; Characterization and Evaluation of Materials; Chemistry and Materials Science; Chromium base alloys; Cobalt base alloys; Grain boundaries; Materials Science; Metallic Materials; Metallurgy; Molybdenum base alloys; Nanotechnology; Nickel base alloys; Sigma phase; Structural Materials; Superalloys; Supersaturation; Surfaces and Interfaces; Thin Films
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-017-4312-6

In current study, two sets of Ni-based alloys (Ni-Cr-Mo and Ni-Cr-Re series) containing 0 to 15 at. pct of Co addition were investigated to understand the formation behavior of TCP phases. Significant difference on the formation behavior of TCP phases and corresponding Co effect was found in two series alloys. TCP precipitates ( P and µ phase) were observed in both grain interiors and boundaries in Ni-Cr-Mo series alloys. Higher levels of Co addition increased the supersaturation of Mo in the γ matrix, which explained that Co addition promoted µ phase formation. In contrast, the TCP precipitates ( σ phase) formed by the manner of discontinuous precipitation transformation in the grain boundaries in Ni-Cr-Re series alloys. More Co additions suppressed the formation of σ phase, which was mainly attributed to the decreased supersaturation of Re in thermodynamically metastable γ matrix. The information obtained from simplified alloy systems in this study is helpful for the design of multicomponent Ni-based superalloys.