Microstructure and Properties of TiAl Composite Coatings Prepared by Laser Cladding under Multi-Phase β0/CoAl2Ti Phase Strengthening

Ceramic-reinforced TiAl matrix composite coatings are fabricated by laser cladding on Ti-6Al-4V (TC4) surfaces. The present work focuses on matching of the ceramic phase with the TiAl matrix to achieve a strength–toughness matching through the multi-scale multi-phase structure. The results indicated that the structure of composites coatings, including γ, α2, β0, CoAl2Ti, and TiC phases, significantly improved the properties of the composite coatings. The TiAl composite coating reached a maximum hardness of 741.17 Hv0.2, and the 10 at% tungsten carbide (10 WC) coating has the lowest wear volume of 8.8 × 107 μm3, the friction performance was approximate five times that of TC4. Detailed explanation of the friction properties and friction mechanism of the composite coating based on crystallographic orientation relationships and nanoindentation results. The study found that strength–toughness matching is important for the improvement of friction performance. Based on the TiAl alloy generated in the non-equilibrium solidification state in this paper, the solidification process and microstructure evolution are analyzed in detail.