High wear resistance of uniform nitriding titanium composites fabricated by in-situ laser powder bed fusion

Laser powder bed fusion (LPBF) supplies a new method for titanium matrix composites (TMCs) that are difficult to process using traditional production. Aiming at the current LPBF-printed pure titanium with low hardness and poor wear resistance, this paper proposes an innovative method of laser in-situ synthesis of uniform nitriding TMCs under the interaction of Ar + 0/5/10/15 % N2 with Ti powder in the LPBF process. It is shown that the forming quality can be modulated by the laser energy density and N2 concentration. TiN was in-situ synthesized in more than 10 % N2. Moreover, the hardness and wear resistance of LPBF-ed TMCs increased with rising N2 concentration. The friction coefficient decreased from 0.39 under Ar to 0.32 of 15 % N2, and the wear rate decreased by 70 %. Besides, this study provides a reference for in-situ synthesis of gradient TMCs with high hardness and wear resistance on the surface, while the inner is ductile.