Interfacial structure and wear properties of selective laser melted Ti/(TiC+TiN) composites with high content of reinforcements

Abstract High-fraction ceramic particulate-reinforced titanium matrix composites were manufactured by selective laser melting (SLM) from starting powders containing Ti-TiC, Ti-TiN, Ti-TiC-TiN and Ti-TiN-graphene. The microstructures of the composites were characterized to reveal the constitution of the reinforcements, the matrix as well as the formation of interfacial structure via ex-situ and in-situ synthesis routes. The microhardness of the SLM-fabricated composites is at least three times higher than that of unreinforced Ti due to high density of hard ceramic reinforcements. A coefficient of friction (COF) value of 0.792 and a wear rate of 1.0×10-4 mm3/N-1m-1 were obtained for the SLM-processed Ti/(TiC+TiN) composites by ex-situ addition of TiC and TiN ceramic particles due to the favorable interfacial structure formed between these hybrid reinforcements and good manufacturing quality. This study proposes a unique interfacial structure by combination of hybrid reinforcements that allows to improve the manufacturing quality and wear properties of SLM-fabricated titanium matrix composites.