Selective Laser Melting (SLM) of M50NiL—Enabling Increased Degrees of Freedom in New Design Concepts

Abstract

Additive manufacturing methods are becoming more and more important due to improvements in the technologies used for “printing,” although additive manufacturing remains a very expensive technology. As such, additive manufacturing is predominantly used in aerospace or medical applications for complex parts that cannot be manufactured with conventional methods. M50NiL, a carburizing heat-resistant steel, is typically used for main shaft bearings in aerospace gas turbine engines. A selective laser melting process for M50NiL was developed for such applications. Analysis of microstructure, hardness, and tensile and rolling contact fatigue testing demonstrated equivalence of M50NiL AM components to components of conventional M50NiL. This equivalence enables new degrees of freedom in designs for main engine shaft bearings (e.g., the integration of oil cooling channels in the outer ring). A comparison of theoretical optimized cooling channel designs and those possible via additive manufacturing was performed considering geometry, surface roughness, and location of the cooling channels.