Mechanical and electrical characterisation in age hardened Waspaloy microstructures

Abstract

Nickel-base superalloys such as Waspaloy possess excellent mechanical properties at elevated temperatures. This is possible through precipitation hardening, whereby submicron precipitate phases (γ′) are formed in the nickel-rich matrix phase (γ) under controlled aging heat treatments. The current work is focused on studying microstructural evolution in systematically aged Waspaloy specimens through mechanical and electrical characterisation conducted via Vickers microhardness and four probe resistivity measurements respectively. Four bars of industrial grade Waspaloy were solution treated at 1145°C and aged at temperatures of 600, 725, 800 and 875°C for times ranging from 2 min to 763·5 h. For the specimens aged at 600 and 725°C, the maximum in hardness was not reached. However, maxima in hardness and conductivity occur at similar aging times for the samples aged at 800 and 875°C. The present studies indicate that conductivity measurements show potential for ascertaining the hardness of the alloy relative to the over-aged state.