Enhancing microstructural control, tribological and electrochemical performances of laser powder bed fusion processed nickel superalloys through in-situ remelting

Abstract

Laser remelting stands as a fundamental technique in augmenting microstructure and properties for alloys. In this study, the microstructural development, tribological and electrochemical behaviors of laser powder bed fusion (LPBF) processed Inconel 718 with variations in in-situ remelting scan speed (v) were investigated. At an optimal v of 1200 mm/s, a remarkable confluence of superior wear resistance (wear rate: 5.78 ×10−6 mm3/N·m) and corrosion protection (corrosion current density: 0.72 ×10−6 ± 0.1 Acm−2) were achieved. These enhanced surface properties were intricately linked to factors such as heightened densification, carbide precipitates, and a substantial prevalence of low angle grain boundaries (LAGBs). Contrastingly, escalation of v to 2000 mm/s led to insufficient laser remelting energy and rapid cooling rates, resulting in heightened surface roughness (Ra: 12.39 µm) and reduced LAGBs (29%). These alterations weakened contact pressure tolerance during sliding, and facilitated additional corrosion pathways, accelerating intergranular corrosion and diminishing wear resistance. This study underscores the indispensable necessity for meticulous control of remelting parameters to achieve optimal performances, thereby imparting valuable insights for advancing additive manufacturing techniques.