Effect of heat treatment on microstructure and tribological performance of PH 13-8Mo stainless steel fabricated via wire arc additive manufacturing

Abstract

The scratch and reciprocating sliding wear response of a PH 13-8Mo stainless steel fabricated by wire arc additive manufacturing (WAAM) are investigated after different cycles of post-printing heat treatments and correlated with the microstructure and mechanical properties. The performed heat treatment cycles comprised of solutionizing for 1 h at 1050 °C followed by an aging cycle for 4 h at 400 °C, 500 °C, and 600 °C. The optimum aging temperature was found to be at 500 °C under which hardness, scratch, and wear resistance were maximum and the coefficient of friction was minimum due to removal of determinantal δ-ferrite phase from the as-printed microstructure and the attained precipitation hardening through the formation of coherent nano-scale β-NiAl precipitates. The employed heat treatment was effective in eliminating the anisotropic scratch and wear response in the as-printed part arising from its anisotropic microstructure. The overall wear micro-mechanisms were similar for as-printed and heat-treated conditions with ploughing during scratch test, and adhesive, oxidative, and three body abrasive wear mechanism during the reciprocating sliding wear test. The results showed that WAAM-produced PH 13-8Mo parts have great potential to be an alternative to their wrought counterparts for wear resistance demanding applications.