40 / 2021-06-29 09:56:11

Effect of Si content on Microstructure and Tribological Properties of NiTi laser cladding coatings

laser cladding,NiTi coatings,Ti5Si3,wear resistance

NiTi_98-xSi_xC₂ (x = 0, 4, 8 wt.%) coatings were prepared on Ti6Al4V substrate by laser cladding to improve the surface mechanical properties of NiTi coatings. The effects of Si content addition on the microstructure, phase composition, microhardness, and tribological properties of the coatings were systematically analyzed. The results show that the NiTi_98-xSi_xC₂ (x = 0, 4, 8) coatings are mainly composed of NiTi, NiTi_2, and TiC phases. The rod-like second phase of Ti₅Si₃ was found in NiTi₉₀Si₈C₂ coating, while the rod-like phases were found broken. The fragmentation of the rod-like phase is related to the growth of the NiTi phase around it. At the same time, TEM results show that the NiTi (B2) phase and Ti₂Si second phase are exited in the NiTi₉₀Si₈C₂ coating. Ti₂Si, which has not been decomposed into Ti₅Si₃, remains during the laser cladding process. In addition, the eutectic structure in NiTi₉₀Si₈C₂ coating was observed in some regions. The average microhardness of the NiTi_98-xSi_xC₂ (x = 0, 4, 8) coating were at 534.08 HV_0.5, 598.06 HV_0.5, and 974.08 HV_0.5, respectively. The wear resistance of NiTi_98-xSi_xC₂ (x = 0, 4, 8) coatings increased with the increased Si content. The above analysis confirms that the Optimal tribological properties were NiTi₉₀Si₈C₂ coating.