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 degreesC 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 gamma/gamma' regions early in the heat treatment cycle at temperatures up to about 1340 degreesC. 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 degreesC 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. (C) 2001 Elsevier Science B.V. All rights reserved.