Effect of cold rolling and subsequent aging on tensile properties and thermoelastic coefficient of Ni-Span-C 902 superalloy

Abstract

The influence of cold rolling and subsequent aging on tensile properties and thermoelastic coefficient (TEC) of Ni-Span-C 902 superalloy was investigated. The solution treated specimens conventionally cold rolled to 30–50% thickness reduction and subsequently aged at different temperatures ranging from 550 to 850 °C for 5 h. The results of room temperature tensile tests indicated that higher strength and elastic modulus are achieved by increasing the amount of reduction area from 30 to 50%. Also, the maximum tensile strength and elastic modulus are obtained in the specimens which were 50% cold-rolled and subsequently aged at 650 °C for 5 h. Microstructural evaluation revealed that fine and spherical γ’ phase with size of 80 ± 20 nm is precipitated during aging at 650 °C. By increasing aging temperature from 650 to 750 °C, coarse γ’ phase is obtained and consequently UTS is declined. The evolution of ɛ phase is observed as a result of aging at 850 °C. According to tensile test it can be demonstrated that ɛ phase decreases the UTS and increases the ductility of the alloy. Tensile test results in the range of 30–100 °C showed that by increasing the aging temperature from 550 to 650 °C, TEC increases and with increasing the amount of cold rolling from 30 to 50 pct, TEC decreases. Meanwhile the lowest TEC value is obtained with aging of the 50 pct cold-rolled specimens at 550 °C.