Microstructure evolution and mechanical properties of H13 steel produced by Selective Electron Beam Melting

Abstract

As one of the additive manufacturing technologies, the Selective Electron Beam Melting (SEBM) process several advantages over Selective Laser Melting (SLM), including faster scanning velocity, higher energy utilization and higher preheating ability of up to 1100 °C. Thus, it is particularly advantageous for the production of high melting point and brittle metals, like the medium carbon high-alloy H13 steel. This study presents a systematic investigation of the microstructural evolution and mechanical properties of H13 steel fabricated using Selective Electron Beam Melting (SEBM) with varying deposition heights. The manufactured samples were examined using high-tech measuring instruments to evaluate different properties such as phase composition, microstructure, microhardness and grain morphology. The results reveal that the microstructure of the as-built SEBM-H13 sample consists of martensite, bainite, and residual austenite with a typical cellular/dendritic structure. As the deposition height decreases, the grain morphology degrades, and the grain boundary undergoes carbide precipitation ((Cr, Fe)7C3) and growth. Consequently, the sample exhibits a gradient hardness structure in the building direction with the highest hardness of 565.6 (±5.8) HV0.5 at the top surface, followed by a distinct decrease in hardness to approximately 506.7 (±3.3) HV0.5 at increased distances from the surface. This study provides a fundamental understanding of fabricating high-performance H13 steel using SEBM.