Coarsening behavior of γ′ precipitates of single crystal Ni-based superalloys during long-term exposure

• Published in: Materials letters 2019-04, Vol.241 (C), p.210-213
• Main Authors: Pan, Yanming, Zhang, Longfei, Huang, Zaiwang, Jiang, Liang
• Format: Article
• Language: English
• Subjects: Chemical precipitation; Coalescing; Coarsening; Coarsening rate; Creep strength; Design optimization; Exposure; High temperature; Materials science; Metals and alloys; Microstructure; Mo:W ratio; Molybdenum; Ni-based single crystal superalloy; Nickel; Nickel base alloys; Organic chemistry; Phase stability; Precipitates; Single crystals; Superalloys; γ′ precipitates
• ISSN: 0167-577X; 1873-4979
• DOI: 10.1016/j.matlet.2019.01.066

•The microstructure evolution of γ′ precipitate was studied.•The coarsening rates of the γ′ precipitates is accelerated with increasing Mo:W ratio.•The coalescing of γ′ precipitates is aggravated with increasing Mo:W ratio. The phase stability of γ′ precipitates in single crystal Ni-based superalloys at the elevated temperature is inherently associated with creep performance. During high temperature in-service exposure, the coarsening of γ′ precipitates typically occurs and further results in coalescing that is regarded as an indicator of degradation of creep resistance. In this research, we design three single crystal Ni-based superalloys by means of solely tuning Mo:W ratio to investigate their coarsening behaviors upon different temperatures (950–1050 °C) and exposure times (0–500 h). The experimental results showed that the coarsening rate of γ′ precipitates increases with increasing Mo:W ratio. The coarsening kinetics are adequately characterised by the classical LSEM model. The experimental results can be used to optimize the design of alloy chemistry.