Phase Transition and Atomic Competition Mechanism of In-Situ Particle Reinforced TixAl/Ti5Si3 Composite Coating Prepared by Laser Cladding Al-xSi-2Nb Alloy Powder on Ti6Al4V Alloy

The in-situ particle reinforced TixAl/Ti5Si3 composite coatings with excellent wear resistance were successfully fabricated by laser cladding Al-xSi-2Nb alloy powder on Ti6Al4V alloy. The microstructure evolution and properties were systematically studied. Meanwhile, the phase transformation and atomic competition of the composite coatings were also investigated based on the Ti-Al-Si phase diagrams and the self-consistent bond length difference (SCBLD) method. The results indicate that a large number of in-situ particle reinforced phases, such as Ti5Si3, α2-Ti3Al and γ-TiAl, exhibit in the composite coatings. Moreover, the morphology and quantity of in-situ particle reinforced phases are significantly affected by laser cladding parameters. The fabricated coatings not only own a good and narrow metallurgical bonding (MB) with the substrate, but also have the excellent wear resistance. The Ti5Si3 atom cluster owns the significant advantage in the atomic competition to form embryo and bulk crystals; while the α2-Ti3Al phase is easier formed than γ-TiAl phase during the decomposition of β solid solutions. Moreover, the V and Nb elements are easier dissolved in α2-Ti3Al phases than that of γ-TiAl phase.