Selective laser melting of P20 mould steel: investigation on the resultant microstructure, high-temperature hardness and corrosion resistance

摘要

Additive manufacturing (AM) & 3D printing can realise rapid delivery of high-quality and complex-geometry industrial product like steel mould with conformal cooling channels. In this paper, selective laser melting (SLM), a typical AM technique, was used to investigate the processing of P20 tool steel which is commonly used for plastic mould. SLM processing parameters, including scanning speed and laser power, were investigated to produce test specimens with high density. High cooling rate induced formation of refined dendrite and major crystalline phases in the as-printed P20 are identified largely as martensite, with an additional small portion of retained austenite. A subsequent tempering heat treatment has been done to eliminate these metastable phases and guarantee overall structural stability and mechanical property of the as-printed P20. Hardness at 250 degrees C and corrosion resistance in 3.5 wt-% NaCl aqueous solutions were measured to evaluate the reliability of P20 mould steel under service, which show rather satisfactory results.