Selective laser melting of 24CrNiMo steel for brake disc: Fabrication efficiency, microstructure evolution, and properties

•24CrNiMo alloy steel part was successfully fabricated via SLM with high power input.•The microstructure was granular bainite/meta bainite duplex microstructure.•Fabrication efficiency was greatly improved by high power input and thicker powder layer processing parameters.•High power input leads to high thermal accumulation level and bainite type microstructure formation.•Both of the UTS and YS are higher than the wrought tempered microstructure criterion. 24CrNiMo alloy steel used for brake disc was prepared by selective laser melting technology with the processing parameters of high power input and thicker powder layer. The Microstructure and mechanical properties of as-fabricated part were characterized. Effects of processing parameters on the production efficiency, thermal history and microstructure evolution mechanism were studied. The results of this work indicate that the as-fabricated steel microstructure mainly consist of granular bainite and meta bainite, which results in a high microhardness and fine strength. High laser power input leads to a high thermal accumulation level in a SLM process and the microstructure mainly transforms into bainite. In addition, compared to the commonly used parameters, the overall preparation efficiency in this study is enhanced by 82.9%. These presented results provide an insight on how to improve SLM efficiency, and preparation of high-performance 24CrNiMo alloy steel by SLM technology shows high potential for manufacturing of the brake disc core part.