Dependence of the wear resistance of additive-manufactured maraging steel on the build direction and heat treatment

Abstract

The aim of this research work was to study the effect of the build direction and heat treatment on the anti-wear properties of maraging steel produced by laser powder bed fusion (LPBF) and how these properties correlate with the resulting mechanical properties. The investigation involved a commercial EOS laser power bed fusion system which included horizontal, vertical and inclined (45°) build directions. After the additive manufacturing the specimens were subjected to aging or solution treatment and aging, after which the wear and mechanical properties were evaluated in different build directions. The results show that even after aging build direction of AM maraging steel parts plays an important role in terms of mechanical and wear properties. After aging the interfacial features between the laser tracks tend to disappear, with the cellular sub-structures being broken into particles. However, although broken and diminished, the cellular sub-structure, defects, nano-segregations and a weak texture in the build direction are still present after aging. This results in lower strength and elastic properties as well as reduced resistance to crack initiation for vertical printing direction. On the other hand, it still provides superior resistance to crack propagation. Best combination of abrasive and adhesive wear is obtained for horizontal direction and in-plane sliding, while sliding across the layers is the most detrimental. Inclined printing bypasses anisotropy and provides good combination of high strength and toughness. However, it is inferior in terms of wear resistance. Properties anisotropy can also be eliminated by a solution treatment, which homogenizes the microstructure and improves toughness, but may also result in reduced strength and wear resistance. • Investigated the effect of building direction and heat treatment on properties of AM maraging steel. • Even when aged building direction plays an important role on mechanical and tribological properties. • Horizontal direction gives higher strength, resistance to crack initiation and wear resistance. • Vertical direction is superior in terms of resistance to crack propagation. • Solution treatment homogenizes microstructure and eliminates properties anisotropy.