Preparation of Knife with Self-sharp Edge by Laser Caldding Ni-based WC Composite Coating

To increase wear-resistant and form self-sharp edge of agricultural knives，Ni-based WC coating was prepared on one side of cutting edge at knives of 65Mn steel by using semiconductor laser equipment under the way of coaxial powder feeding.Microstructure，chemical and phase composition of coating were analyzed utilizing SEM，EDS，and XRD.The micro-hardness and wear-resistant were investigated by micro-hardness tester and wear-resistant tester.Results showed that the laser cladding composite was uniform and dense in microstructure and metallurgical combination was formed between laser cladding and matrix.Part of WC particles was melted and decomposed during coating preparation.At the same time，a large number of hard phases（WC，W2C，Ni31Si12，Fe3Ni3B，Cr7C3，Cr23C6，CrB，etc）were generated，which increased hardness of coating layer greatly.As the increase of laser power，the atomic diffusion between coating and knife matrix was improved.But coating hardness reduced slowly.Average hardness of coating was about 1000（HV 0.2），which increased wear-resistant and satisfied requirement of self-sharp edge of agricultural knives.