Comparative Study of Heat Treatment Routes for Enhancing High-Temperature Wear Resistance of EBM-Processed Inconel 718

Abstract

Additive manufacturing of nickel-based superalloys such as Inconel 718 via electron beam melting (EBM) has gained increasing attention for aerospace applications; however, challenges related to surface hardness and hightemperature wear resistance remain, highlighting the need for systematic post-processing strategies. In this study, the effects of several post-processing heat treatments-solutionizing, solutionizing + aging, boronizing, and boronizing + aging-on the microstructure and high temperature wear behavior applied of electron beam melting (EBM) additive-manufactured Inconel 718 were investigated. The materials were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), microhardness measurements, and high-temperature wear tests. The results showed that solutionizing and solutionizing + aging produced a more homogeneous structure compared to the as-built condition, while boronizing and boronizing + aging significantly increased the surface hardness, leading to a notable improvement in hightemperature wear resistance. The wear resistance followed the order: boronizing, boronizing + aging, solutionizing + aging, solutionizing, and as-built condition. The improvement in wear resistance through aging after solutionizing was attributed to the microstructural refinement involving the formation of gamma' and gamma" precipitates and carbides, which improved the strength and wear resistance. However, aging after boronizing weakened the hard boride layer due to coarsening and localized diffusion of boron into the core. Hardness played a crucial role in the effective wear mechanism: abrasive wear was prevalent in the as-built, solutionized, and solutionized + aged specimens, whereas microcracking was a significant mechanism in the boronized and boronized + aged specimens. With increased wear test temperature, oxidative wear and adhesive transfer became more pronounced, regardless of the post-processing treatment.