MECHANICAL PROPERTY OF SINGLE PHASE Co-Ni-Cr-Mo BASEDSUPERALLOY PRODUCED BY COLD WORKING AND RECRYSTALLIZATION HEAT TREATMENT

초록

Mechanical property of carbon-free Co-Ni-Cr-Mo based superalloy was investigated in the temperature range from room temperature to 1073 K. Cold working and subsequent recrystallization heat treatment was carried out to produce an equiaxed grain structure. The average grain size was controlled to 28-238 ? in order to understand the effect of grain size on mechanical property and flow behavior. At room temperature and 943 K, 0.2% offset yield strength increased with decreasing grain size to exhibit grain size dependence. At 1073 K, a sample with average grain size of 42 ? showed higher yield strength than that obtained with a sample having average grain size of 28 ?. A serrated flow behavior was found in the sample tested at 943 K and at 1073 K, while no serrated flow was displayed in the sample tested at room temperature. Mechanical twinning was observed in the wide temperature range, which is closely correlated with flow behavior.