Super-Solvus Heat Treatment Study of Novel Nickel-Based Superalloy

This work investigated the influence of heat treatment processes on the gamma' phase microstructure of a novel third-generation nickel-based powder superalloy WZ-A3. Differential thermal analysis of different heating and cooling rates, interventional cooling tests, super-solvus cooling rate tests and aging heat treatment experiments were carried out in order to investigate the dissolution and precipitation behavior of gamma' phase as well as its size evolution. The results indicate that when the WZ-A3 alloy is cooled at different cooling rates during super-solvus heat treatment, the initial precipitation temperature of gamma' phase is between 1148 similar to 1165 degrees C, the fastest precipitation temperature is between 1028 similar to 1037 degrees C. More secondary gamma' phase precipitation can be obtained using a slower cooling rate. The temperature of the super-solvus heat treatment has no significant effect on the size of the secondary gamma' phase. The cooling rate after solution heat treatment is inversely proportional to the size of the gamma' phase. This relationship can be expressed as a power law function y=1490.74x(-0.509), where y is the size of the gamma' phase (nm), x is the cooling rate (degrees C/min). Short-time aging at 800 degrees C has no obvious influence on the size and morphology of the secondary gamma' phase. The activation energy of the gamma' phase coarsening of the studied alloy is 278 kJ/ mol. se