Effect of SiC content on microstructural evolution and tribology properties of laser-clad TiC-reinforced Ti-Al-Si composite coatings

This work prepared (Ti-Al-Si)-X (x = 1, 2, 3, 4) coatings on TC4 alloy matrix composites by laser cladding to improve their surface mechanical properties. Meanwhile, the effect of the content of SiC added to the Ti-Al-Si system on the properties and microstructures of the original coatings was explored. The results showed that the reinforced composite coatings contained matrix phases (TiAl, Ti3Al, TiAl3) and reinforcing phases (Ti5Si3 and TiC). As SiC content increased, the matrix phases formed in the coatings showed different results on the Ti-Al-Si ternary phase diagram due to the introduction of C, a stabilizer of ɑ-Ti alloy. Meanwhile, TEM results indicated the existence of Ti5Si3 phase and Ti3Al secondary phase in the Ti-Al-Si-3 layer. Compared with the TC4 matrix, the reinforced composite coatings had higher microhardness with average values of 780.9 HV0.3, 853.9 HV0.3, 985.0 HV0.3 and 943.5 HV0.3 for the four coatings, respectively. The wear resistance of the reinforced composite coatings increased first and then decreased with increasing SiC content, which was the result of the matrix phase transformation. The Ti-Al-Si-3 coating had the highest microhardness (1092HV0.3) and wear resistance (the friction coefficient, the wear scar width and wear weight loss were 0.37, ∼0.83 mm and 1.8 mg, respectively). The above analysis and results demonstrated that the Ti-Al-Si-3 layer had superior mechanical properties compared with those of other reinforced coatings.