Microstructure and wear resistance of laser melted Ti₅Si₃ / NiTi intermetallic alloys

Novel wear resistant alloys with metal silicide Ti₅Si₃ used as the reinforcing phase and intermetallic NiTi as the matrix were designed and fabricated by the laser melting process with different compositions of Ti-Ni-Si alloy powders. Microstructure, Vickers microhardness and dry-sliding wear resistance as a function of Ti₅Si₃ content were investigated. The results indicate that the as-solidified microstructure of the alloys transforms from hypoeutectic to eutectic and hypereutectic, respectively as the Ti₅Si₃ content increases. The reinforcing phase Ti₅Si₃ has a significant effect on the microhardness and the wear resistance of the alloys. The laser melted Ti₅Si₃/NiTi intermetallic alloys have excellent wear resistance under dry-sliding wear test conditions. Wear resistance of the intermetallic alloys is up to 40-90 times higher than the hardened ball-bearing steel GCrl5 and increases noticeably with increasing of content of Ti₅Si₃ reinforcing phase. The excellent wear resistance of Ti₅Si₃/NiTi intermetallic alloys is attributed to the effective reinforcement of Ti₅Si₃ phase and the excellent toughness and pseudo-elasticity of NiTi phase.