Study On Properties Of Micro-Nano WC-Ni60A Composite Coating By High Frequency Induction Cladding

The micro-nanostructured tungsten carbide (WC) reinforced Ni60A alloy composite coatings were produced on Q235 mild steel by high frequency induction cladding. The thickness of coating was 0.8³mm. Microstructure is examined by means of optical microscope scanning(OM) and scanning electron microscope (SEM). Phase compositions were analyzed by X-ray diffraction (XRD) and SEM-EDS. The microhardness and Surface Rockwell hardness were tested on micro-hardness instrument and Surface Rockwell hardness tester. Abrasive wear resistance was performed on MLS-225 wet sand/rubber wheel tester. Influence of micro WC content, addition of nano WC and induction heating parameter on microstructure, phase compositions and wear behaviour were studied. The results showed that:(1)With 50% micro WC content, composite coating(A5) showed homogeneous microstructure, less micro WC particles uniformly distribute in the Ni solution matrix and less defects. With 50% WC coating showed the better abrasive wear resistance and about 6.5 times higher than Ni60A coating in the same condition. Composite coating mainly consisted of hard-phases as WC,W₂C,Cr₇C₃,Cr₂₃C₆,Cr₂B,Ni₂B,Ni₃Si, etc.(2)When total content of micro WC was 50%, adjusting micro and nano WC contents, the result showed that wear resistance decreased and defects increased. With continue adding more nano WC in 50% micro WC, coating was more homogenious and compact. The hardness and wear resistance of the composite coating was obviously reinforced by more hard phase W2C.(3)Fusion course of the coating was half-fusion(46s)-fusion-superfusion(54s). C3 coating (heating time was 50s) was composed major WC phases, with least defects, high hardness and excellent wear resistance. When heating time up to 54s, WC decomposed badly, and generated reticulate or flocculent structures as (Fe,W,C) phases, which decreased wear resistance of coating.Wet sand/rubber wear mechanisms of the composite coating was evaluated. The results showed that: predominant wear mechanism was slight micro-ploughing and brittle peeling of hard phases.