An investigation on graphite behavior and coating properties in the molten pool based on different powder particle sizes

This paper aims to explore the influence mechanism of powder particle sizes on the microstructure and properties of coatings and identify the effect of powder particle size difference on the coating graphite phase. NbC-reinforced Ni-based coatings were in-situ synthesized by laser cladding to investigate the impact of powder particle sizes on the morphology, structure, and properties of coatings. The results indicate that increasing powder particle size enlarges the coating area and decreases the coating width and dilution ratio. Meanwhile, the defect ratio first increases and then decreases. The XRD test suggests that the coating mainly consists of NbC, solid solution (Fe, Ni), B(4)C, Cr(2)C, and CrB(2.) Different powder particle sizes do not change the phase composition of coatings but affect the graphite phase morphology. The morphology transforms from spherical to flocculent as the powder size varies from micrometer to nanometer. The hardness of coatings gradually increases, and the friction and wear properties decrease with the growth of powder particle size. The dispersed graphite phase in the nano coating plays a self-lubricating role in the friction and wear process. This research provides a reference and theoretical basis for selecting powder particle size in laser cladding.