Effect of heat treatment and electric discharge alloying on the lubricated tribology of Al–Si alloy fabricated by selective laser melting

Abstract

Selective Laser Melting (SLM) is an innovative additive manufacturing technology that facilitates the design and manufacture of complex lightweight parts with improved mechanical properties. The current study investigates the impact of post-processing such as heat treatment and Electric Discharge Alloying (EDA) on the lubricated tribological behaviour of SLM Al–Si alloy at ambient and elevated temperatures in comparison with the tribological behaviour of conventionally cast Al–Si alloy. The lubricated sliding wear experiment conducted using a Pin on Disk (POD) tribometer with EN-31 alloyed steel as a counter body. The EDA treatment is highly appealing and enhanced the wear resistance of SLM Al–Si alloy by 14.07% and 24.07% at ambient and elevated temperatures, respectively. Moreover, the EDA treatment increased the wear resistance of cast Al–Si alloy by 28.82% and 46.28% at ambient and high temperatures, respectively, due to the development of a wear-resistant carbide (SiC) and oxide (Al2O3) rich modified layer on the surface. The T6 heat treatment in SLM Al–Si alloy caused deterioration in wear resistance by 10.74% and 36.73% at ambient and elevated temperature, respectively, due to the coarsening of the finer microstructure formed during SLM. In contrast, the T6 heat treatment in cast Al–Si alloy is highly effective in terms of wear resistance with an improvement of 13.26% and 13.64% at ambient and elevated temperature, respectively, due to the hardening effect caused by heat treatment. The prominent wear mechanism identified for all samples at both experimental conditions is severe abrasive wear due to plastic deformation.