Processing Fundamentals and Performance Investigation of Selective Laser Melting of High‐Speed Steel in Reactive N2 Atmosphere

Abstract

The distinct deposition method of selective laser melting (SLM) enables the near‐net‐shaping of high‐speed steel tools with complex geometries and integrated functions, such as adapted cooling channels, which offers economic advantages and has, thus, attracted considerable attention. However, SLM‐processed high‐speed steels are prone to cracking due to their high carbon and alloying element contents and high internal stresses. Varying the steel composition to stabilize austenite can help to reduce the residual stresses. Herein, the effect of nitrogen atmosphere on the densification behavior, microstructural evolution, and mechanical properties of high‐speed steel in the SLM process is investigated. The results demonstrate that nitrogen can dissolve in the steel. In combination with suitable SLM parameters, this leads to a fully austenitic microstructure with no cracks. After heat treatment, the microstructure of steel transforms into tempered martensite, along with the precipitation of tiny V‐rich M(C,N) carbonitride and V‐rich MC carbide. The hardness and bending strength of the tempered sample reach the highest of 61.3 HRC and 3659 MPa, respectively. Its abrasive resistance is also improved. An alloy design idea is provided that is based on the reactive atmosphere of high‐speed steel and other materials for processing by SLM.