Analysis of thermal load of dies for P/M superalloy isothermal forming

The finite element models of dies used for P/M superalloy disk forming were established, and the heating parameters were optimized based on the thermal-physical property of Ni-11Co-17W-6Al-8Ta alloy. The results show that stress peaks of the dies were lower when they were heated in heating rate range from 0.1°C/s to 0.5°C/s. The effect of holding time on thermal stress decreased when holding time was larger than 4h. This leaded to that the rate of decreasing stress became lower. According stress amplitude-holding time curve, the optimal holding time is between 2-4 h. Moreover, at the heating rate of 0.1°C/s and the holding time of 2 h, the outside surfaces and profile transition zones of dies exhibited stress concentration. The values of stress amplitudes were larger in these regions. However, the results of fatigue test at the temperatures of 1050°C and 1100°C show that the effect of thermal load on crack propagation in above-mentioned regions was slight.