Microstructure and wear resistance of laser cladding Ti-Al-Ni-Si composite coatings

To enhance the tribological performance and avoid the surface failure of TC4 alloys under severe wear condi-tions, Ti-30Al-16Ni-3Si, Ti-48Al-3Si, and Ti-50Al (at. %) coatings were fabricated on TC4 substrate by laser cladding. The coatings' composition, microstructure, microhardness, and wear resistance were investigated through XRD, SEM, TEM, and performance testing methods. The phase constituents in the Ti-50Al coating were TiAl and Ti3Al, while Ti5Si3 and Ti5Si3-TiAl eutectic structure formed in the Ti-48Al-3Si coating. The phase constituents in the Ti-30Al-16Ni-3Si layer were the matrix phases of Ti2Ni and Ti3Al and the reinforcement of Ti5Si3. Meanwhile, Ti2Ni-Ti-3-Al eutectic structure and Ti5Si3-Ti2Ni eutectic structure were also formed. Ti-30Al-16Ni-3Si coating exhibited a higher microhardness and wear resistance, attributed to the interphase distribution of Ti3Al phase and Ti2Ni phase, and the tight combination of Ti3Al-Ti2Ni eutectic structure, which imparted the coating a higher strength and toughness. Compared with the TC4 substrate, the microhardness of the Ti-30Al-16Ni-3Si coating was increased by 2.5 times, and the wear volume loss was reduced by 37 %. The wear mechanism of Ti-50Al coating and Ti-48Al-3Si coating were abrasive wear and adhesive wear, while Ti-30Al-16Ni-3Si coating was mainly adhesive wear.