Long-Time Thermal Structural Stability Study on NiCr20TiAl Alloy

The coarsening kinetics of main strengthening phase gamma' and the growth behavior of grain boundary carbides have been investigated on NiCr20TiAl alloy aged at 550 similar to 750 degrees C for 200 similar to 10,000h. The precipitates of NiCr20TiAl alloy at standard heat treatment condition are gamma', M7C3, M23C6 and MC. The coarsening of gamma' precipitates proceeds by Ostwald ripening controlled by volume diffusion in the alloy. Grain boundary carbides M23C6 and M7C3 increase with ageing times and temperatures. The morphologies of precipitates after long-time ageing almost remain the same as that at standard heat treatment condition except 750 degrees C.