Application of nimonic 80A to the hot forging of an exhaust valve head

Nimonic 80A superalloy with high-temperature strength and high-corrosion resistance is used in jet engines for aircraft, gas turbines for power plant and marine diesel engines, etc. To set favorable hot forging conditions of Nimonic 80A, various mechanical tests such as the hot compression test and the micro-Vicker’s hardness test have been performed under various test conditions. The hardness during hot forging varied depending on the forging temperature, strain rates and strains. From the study, the hardness increases with increasing strain but decreases with increasing forging temperature. Prior to the hot forging of a diesel engine’s exhaust valve head, numerical simulation was executed with DEFORM, a commercial FE code, and a general carbon steel was forged by a screw press for comparing the forgeability of Nimonic 80A and carbon steel. From the study, it is known that optimum conditions of hot forging should be determined carefully by considering forging load and forgeability. The results can be used effectively to set reasonable forging conditions in the hot forging of Nimonic 80A superalloy.