MICROSTRUCTURE AND CHARACTER OF FRICTION AND WEAR OF WC_P/Ni BASED ALLOY GRADIENT COMPOSITE COATING BY WIDE-BAND LASER CLADDING

In order to eliminate cracks produced in the process of laser cladding, a new kind of gradient composite coating is designed. The experimental results indicate that the excellent metallurgical bonding is formed between the gradient composite coating and substrate. There are γ-Ni dendrite structure, γ-Ni+M₂₃C₆ eutectic structure and M₆C,M₇C₃,M₂₃C₆ in the composite coating. With increment of cast WC_P volume fraction,the friction coefficient of the composite coating decreases,but the wear resistance of the coating increases.The wear resistance value of 19-4 sample is 4.61,and is increased by three times on an average as compared with that of the substrate.The wear mechanism of coatings results from a composite action of abrasive wear and adhesive wear.