Fabrication of in-situ composite coating reinforced with TiC particles by powder feeding laser cladding

摘要

A composite coating was produced by powder feeding laser cladding. The detailed laser cladding experiments were conducted on a 3kW continuous wave CC_2 laser. The diameter of the beam was 3mm, the scanning velocity was 3-10mm/s, and the powder feeding rate was 3.26g/min. The chemical compositions, microstructures and surface morphology of the cladded layer were analyzed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffractometry (XRD). The experimental results showed that a composites coating with TiC particles of various shapes and sizes embedded in nickel based alloy could be in-situ synthesized from the mixture of nickel based alloy powder, graphite enwrapped with nickel and titanium powders by powder feeding laser cladding. An excellent bonding between the coating and the carbon steel substrate was ensured by the strong metallurgical interface. The coating is uniform, continuous and free from cracks, however there existed some pores in coatings. The microstructure of the coating was mainly composed of γ-Ni dendrite, a small amount of CrB, TiB_2, M_(23)C_6 and dispersed TiC particles. The maximum microhardness of the coating was about HV_(0.2) 1100 after laser surface remelting·4.5 times larger than that of the steel substrate.