Conventionally and SLM-manufactured 18Ni300 steel: mechanical and tribological behaviour in dry sliding against PP40 composite

The great mechanical performance of 18Ni300 maraging steel, achieved during ageing treatment by the precipitation of fine intermetallic precipitates within a martensitic matrix, makes this material a good choice for demanding applications such as injection moulds for the automotive industry. Its ease of manufacture by selective laser melting (SLM) allows parts with a higher degree of complexity and the possibility of customised design. Nevertheless, a comprehensive analysis of the performance of the manufactured parts is important to understand the differences between components manufactured by SLM and those produced by conventional methods. In this work, the mechanical performance of a maraging steel 18Ni300 manufactured by SLM was compared with that of a commercial cast steel 18Ni300, as well as their tribological performance during dry sliding against a polypropylene matrix composite reinforced with 40 wt% E-glass fibres (PP40), a material commonly used in automobile parts and known for its abrasiveness. The results show that the steel manufactured by SLM and aged at 510 ºC for six hours has higher hardness and better mechanical properties than the cast steel. Dry sliding wear tests of the aged steels against PP40 showed a 33% lower specific wear rate for the steel manufactured by SLM compared to the cast steel. These results can be explained by the refined microstructure resulting from the rapid cooling during the SLM process. Different wear mechanisms were found: abrasion was the predominant mechanism for the steel manufactured by the SLM process, while abrasion and adhesion were observed for the cast steel.