23:T41e,

Cr₃C₂–Ni composite coatings were fabricated on Ti–6Al–4V substrate by laser cladding using powder mixture of NiCrBSiC alloy and Cr₃C₂. Results of the analysis show that the microstructure and microhardness of the coatings depend strongly on the specific laser energy. With a relatively low specific laser energy (133·3 J mm⁻²), Cr₃C₂ particles were partially dissolved into melted Ni based alloy, and the coating was formed of undissolved Cr₃C₂ particles and cannular Cr₂₃C₆ uniformly distributed in cellular γ-Ni and eutectic matrix. With a higher specific laser energy (266·7 J mm⁻²), more Cr₃C₂ particles were dissolved, and the coating consisted of γ-Ni, TiC dendrites and lamellar CrB. When the specific laser energy is 133·3 and 266·7 J mm⁻², the microhardness of the coating is 500–700 HV and 700–1000 HV, respectively.

24:T4c0,

Laser cladding Ni-based composite coating was fabricated on the surface of 42CrMo steel using 6 kW fibre laser. By the addition of Mo powder, a well-formed and crack-free laser cladding composite coating was obtained. The morphology, composition, microhardness and wear resistance of composite coatings were studied using a scanning electron microscopy, an energy-dispersive spectroscopy, an X-ray diffraction spectrum, a microhardness tester and a wear tester. The results show that the cladding layer has metallurgical bonding with the substrate. The main phases of Ni45 + 10%Mo laser cladding layer are (Fe, Ni), Cr23C6, Cr3C2, Mo2FeB2 and Cr2B3. After the addition of Mo powder, the size of the microstructure of composite coatings is finer than that of Ni45 cladding layer. Stubby-rod carbides are displayed in the interdendritic interface. The molybdenum and chromium are rich in the grain boundaries. The distribution of hardness is uniform in Ni-based cladding layer, and its microhardness is significantly higher than that of the substrate. Ni45 + 10%Mo composite coating has the best wear resistance. Its wear resistance reaches 1.734 times of Ni45 coating and 2.367 times of 42CrMo steel.

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Laser clad Cr 3 C 2 –Ni composite coating on titanium alloys

A study of laser cladding NiCrBSi/Mo composite coatings