Spherical WC Wear-Resistance Metal Matrix Composite Coating Produced By Argon-arc Clad Injection

To overcome problems of burning, dissolution, sinking of WC cermet particles and cracking in WC reinforced composite coatings, the argon-arc clad injection (ACI) was used to make WC particle reinforced wear-resistance composite coating. By clad-injecting 250~420μm spherical WC cermet particles on the surface of a Q235 steel substrate pre-coated with nickel-based self-fluxing alloy, a wear resistant composite coating with non macro-defects, particles distributed uniformly and densely, metallurgically bonded to the substrate, was successfully produced.Based on the study of the ACI technological process, the rationality of overlapping methods, structure and formation of microstructure in different parts of the composite coating were studied. In addition, wear resistance and wear mechanism were studied. With optimized process parameters, the two methods of sequence overlapping and interval overlapping were tested to make multi-passes overlapped composite coating. The microstructure and composition of the coatings were analyzed by means of scanning electron microscopy(SEM), X-ray diffraction (XRD) and energy diffraction spectrum (EDS). Microhardness and wear resistance were also tested using microhardness tester and sliding wear tester respectively.The results show that crack-free composite coating is successfully obtained with sequence overlapping; while cracks appear in the interval pass produced by interval overlapping.Complex microstructure is found in the ACI composite coating, which consists of WC,γ-(Fe,Ni) and Fe3W3C-Fe4W2C(M6C) phases. W2C phase is found in the overlapped composite coating. In the upper, the middle and the bottom parts of composite coating, the morphologies of dark gray / light grayγ-(Fe, Ni) solid solution are roughly same, but the white carbides are very different, and show mainly herringbone, blocks, small flat-shaped. The microhardness around particles of the composite coating is about HV0.2731.83, 6.5 times higher than that of Q235 steel. The microhardness of overlapped and non-overlapped zone is close. In the same wear conditions, the wear volume of Q235 steel is 23 times as that of the single-pass composite layer, and the wear volume of overlapped layer is 2 times as that of the single-pass composite layer. The abrasion wear is the main wearing mechanism for carbides composite coating, while Q235 steel is adhesive wear, with a little abrasive wear.