Nickel-based Composite Coating Reinforced By Micro/nanometer WC Particles With Laser Cladding

Laser cladding WC particle reinforced metal matrix composite coating can effectively improve the wear resistance of mechanical parts surface and be widely used.However,Micron-sized WC particles（Micro-WC）has a relatively large particle size,which can easily lead to cracks,pores and other defects in the laser cladding layer.Nano-sized WC particles（Nano-WC）has relatively small particle size,which is conducive to refining grain and improving coating quality.In this thesis,the 1535-30Nickel-based composite cladding layers reinforced by Micro-WC particles and Nano-WC particles with different contents were prepared on the surface of NM400steel by fiber laser.The microstructure and properties of Micro-WC and Nano-WC coatings with different contents were studied by optical microscope（OM）,scanning electron microscope（SEM）,X-ray diffractometer（XRD）,microhardness tester,friction and wear tester and electrochemical workstation.The effects of different WC particle sizes on the microstructure and properties of the same WC particle content were compared.The results show that:（1）Adding Micro-WC particles and Nano-WC particles can refine the cladding grains,and the cladding layers are composed ofγ-（Ni,Fe）,Cr₂₃C₆,Ni_2.9Fe_0.7Cr_0.36,Cr₇C₃,Cr₄Ni₁₅W,W₂C and WC phases.（2）After adding Micro-WC particles and Nano-WC particles,the hardness of cladding layer is significantly higher than that of matrix,and with the increase of the addition amount,the microhardness of cladding layer also increases.When the content of Micro-WC particles and Nano-WC particles is 30%,the microhardness of cladding layer is 554.6 HV_0.2 and 590.7 HV_0.2,respectively.When the content of WC particles is both 30%,the effect of Nano-WC particles on the hardness of cladding layer is stronger than that of Micro-WC particles.（3）The wear mechanism of cladding layer after adding Micro-WC particles and Nano-WC particles is mainly oxidation wear and adhesive wear.When the content of WC particles is 30%,the wear resistance of the coating with Micro-WC is 28.13%that of the substrate,and the wear resistance of the coating with Nano-WC is 18.75%that of the substrate.（4）After adding Nano-WC particles and Micro-WC particles to Ni-based alloy powder,the corrosion resistance of the cladding layer is not much different from that of 1535-30 cladding layer,but the corrosion resistance of each cladding layer is much stronger than that of NM400 steel.