Examination of steel compatibility with additive manufacturing and repair via laser directed energy deposition

Abstract

High strength steels are a vital material for aerospace applications but are also prone to damage from fatigue, corrosion, and wear. Additive manufacturing (AM) processes such as laser directed energy deposition (L-DED) offer a means for repairing both the geometry and structure of damaged steels; however, significant variation in tensile properties have been reported following repair. While previous studies have tried to improve performance through postdeposition heat treatment, such practices may not be possible for commercial parts due to risks of distortion and thermal damage to the substrate. Instead, this investigation analyses the role of the intrinsic heat treatment effect on as-deposited tensile properties through a detailed review of both AM and AM repair literature. By assessing a wide variety of high strength steels, the links between conventional heat treatment parameters and steel performance in AM are established, and the role of steel composition understood. This review is supported by additional AM and L-DED repaired samples, with consistent parameters used between steels to ensure similar thermal histories, and eliminate potential discrepancies seen between AM machines. The results demonstrate the effect of intrinsic heat treatment on martensitic and precipitation hardening steels, the role of residual heat and heat extraction through the substrate, and flag potential issues faced by steels at risk of temper embrittlement. Taken together, these findings provide a clear vision for the advancement of AM repair and the optimization of mechanical performance.