Process optimization, microstructure and microhardness of coaxial laser cladding TiC reinforced Ni-based composite coatings

Abstract

Since the precursors for coaxial laser cladding (LC) can be easily customized, less waste, and flexibly applied to the surface of complex parts, LC is a practical and promising approach to fabricate metal matrix composite (MMC) coatings for surface modification or repair compared with selective laser melting, preset powder cladding, gas tungsten arc welding. The precursors for LC MMC coatings are composed of an optimized single alloy powder, hard particles or related elements. However, the process for LC MMC coatings is the same as that for single alloy powder. Since the added materials usually affect the quality of the laser beam, the flow characteristics and the solidification process of the melt pool, the process parameters for LC MMC coatings are often not optimal. Therefore, the coarse TiC particles were firstly added to the commercial Ni45 powder, and the Taguchi method and empirical statistical model are employed to optimize process parameters for LC MMC coatings. A reliable processing map for customized precursors was obtained. Finally, the single-layer multi-track TiC-reinforced MMC coatings were fabricated to verify the correctness of mathematical models. The suitable process parameters combination for LC Ni-based MMC coatings are laser powder of 380 W, scanning speed of 5 mm/s, and powder feed rate of 243.7 mg/s. Moreover, the microhardness of the optimized MMC coating is about 520 HV0.3, which is about 2.5 times that of the substrate.