Effect of heat treatment on mechanical properties of Nimonic 80A were investigated. As the heat treatment containing water-cooling after solution-treatment gave fine precipitated microstructure, specimens heat treated by that method have higher short time tensile strength up to 800°C and hardness, and Charpy impact value is lower than those air cooled after solution treatment. Stress-rupture life at 750°C of the specimens water-cooled after solution-treatment was inferior to the specimens air-cooled after solution-treatment, because the former tends to soften during stress rupture testing.
Aging treatment at 750°C gave maximum aging hardness, but aging treatment at 700°C gave maximum stress-rupture life at 750°C, comparing with the aging between 700° and 850°C. It is because precipitation around grain boundary during stress-rupture testing became remarkable by aging above 700°C.
In carbide-precipitation type alloys, tensile strength and stress-rupture life became longer by precipitation-hardening during tensile test and stress-rupture testing at high temperature, but in Nimonic 80A, tensile strength and stress-rupture life of specimens as solution-treated were inferior to aged specimens.