Solution heat treatment response of a third generation single crystal Ni-base superalloy

The standard solution heat treatment of the third generation, single crystal Ni-base superalloy, CMSX-10, requires temperatures up to 1365°C and lasts a total of approximately 45 h. These high temperatures and long times result in a heat treatment that is costly. To determine if the heat treatment could be simplified and/or shortened to reduce the cost, a detailed study was completed on the standard heat treatment. The solution anneal heat treatment dissolves the eutectic γ/γ′ regions early in the heat treatment cycle at temperatures up to about 1340°C. However, the chemical segregation from the partitioning of elements during solidification, was not eliminated until much higher temperatures were reached. In particular, the segregation of W and Re to the dendrite core was not significantly reduced until temperatures in excess of 1360°C were reached in the heat treatment cycle. Reducing the heat treatment temperature and/or shortening the time of the heat treatment would be expected, therefore, to result in residual segregation of W and Re to the dendrite cores, a locally unstable microstructure, and, possibly, the formation of TCP phases.