Effect of heat treatment on tribological behaviour of welding deposits for hardfacing

Abstract

This paper analyses the effects of post-welding heat treatment on the tribological response of weld metals for hardfacing. Applied load in wear tests was also studied. The deposit was a martensitic steel obtained with a gas metal arc welding metal-cored wire under gas shielding of Ar-2% CO2 and 2 kJ /mm of heat input. Cross sections were obtained from the welded coupon and subjected at 550°C for 2h. These samples, together with the as-welded (AW) specimens, constituted the system under study. Cross sections were also extracted for both conditions for determination of chemical composition, microstructure characterisation, microhardness measurements in addition to friction and metal-metal wear tests in pure sliding at 500, 1250 and 2000 N of applied load. A microstructure composed of martensite and retained austenite was observed for both conditions. The AW sample presented 16% of retained austenite, whereas the heat-treated one presented 8%. Heat-treated coupons showed secondary hardening associated with precipitation phenomena. In the specimens tested at 500 and 1250 N, the wear mechanism was oxidative and the AW specimens presented higher wear resistance and higher friction coefficient. On the contrary, the wear regimen of the samples tested at 2000 N was severe, with the heat-treated ones more wear resistant with a higher friction coefficient.