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

The phase stability of gamma' 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 gamma' 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 degrees C) and exposure times (0-500 h). The experimental results showed that the coarsening rate of gamma' 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. (C) 2019 Elsevier B.V. All rights reserved.