Effect of Powder Size and Volume Fraction of WC on the Microstructure of Laser Cladding WC-NiCrBSi Composite Coatings

Abstract

WC-NiCrBSi composite coatings on 0.45 % carbon steel were fabricated by laser cladding. The volume fraction (33, 43 and 60 vol. %) of WC particles with the powder size of 2 μm, 5 μm and 50 μm were added respectively into NiCrBSi powders to deposit composite coatings. The microstructure of the powders and the coatings were examined by scanning electron microscope (SEM) and X-ray diffraction (XRD). Results show that the compactness and uniformity of the coatings are good when WC particles size was 2 μm and 5 μm. However nonuniform distribution and deposit of WC particles on the bottom of the coating will occur when the powder size of WC particles was 50 μm and the volume fraction of WC was 33 %. When the volume of WC addition was higher than 60 %, the volume fraction of the retained WC particles in the coatings is obviously decreased. The dissolving and decomposing of WC increase with decreasing the powder size and increasing the volume of WC addition and the laser power.