Microstructural characteristics and properties of Stellite 6 coatings on TC4 titanium alloy processed at different laser powers

TC4 titanium alloy is widely used in the petroleum and natural gas industry, but it faces severe friction, wear and corrosion problems in harsh marine and oilfield environments, which limits its large-scale application. Laser cladding technology, as an efficient surface modification method, can prepare high-performance coatings that are metallurgically bonded to the substrate, and is expected to significantly extend the service life of TC4 components. In this study, a continuous fiber laser with a maximum power of 6000 W was used to prepare Stellite 6 cobalt-based alloy coatings on the surface of TC4 titanium alloy. The effects of three laser powers of 1.4 kW, 1.6 kW and 1.8 kW on the microstructure, mechanical properties and corrosion resistance of the coatings were systematically investigated. The results show that the coatings are mainly composed of γ-Co, CoCₓ, M₂₃C₆, TiC and Cr₇C₃ phases. With the increase of laser power, the γ-Co diffraction peak shifts to the left and the lattice distortion intensifies. At 1.4 kW, the coating achieves the finest dendritic structure and the highest average microhardness. In the shale oil medium, the 1.4 kW coating exhibits the best wear resistance, with average friction coefficients of 0.220, 0.243 and 0.261 under 5 N, 10 N and 15 N loads, respectively, and wear amounts of 7.8 mg, 9.1 mg and 10.9 mg, all significantly lower than those of the TC4 substrate. Electrochemical tests show that all coatings increase the self-corrosion potential and reduce the corrosion current density, among which the 1.4 kW coating has the best corrosion resistance, with a corrosion current density of 1.784×10⁻⁸ A/cm², and the most uniform corrosion morphology and the best corrosion resistance. This study provides key process basis and theoretical support for surface strengthening and life extension of titanium alloy components under harsh working conditions.