MICROSTRUCTURE AND PROPERTIES OF IN SITU SYNTHESIZED ZrC-ZrB2/Fe COMPOSITE COATING PRODUCED BY GTAW

A metal matrix composite coating reinforced by ZrC-ZrB2 particulates has been successfully fabricated utilizing the in situ reaction of Zr, B4C and Fe pre-placed mixed powders by gas tungsten arc welding (GTAW) cladding process. Various volume fraction of ZrC-ZrB2 particulates composite coatings were produced through cladding different weight ratios of Zr+B4C (30%, 50%, 70%) to improve the wear resistance of AISI1020 steel substrate. The Microstructure of the coating was analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive spectrum (EDS), meantime microhardness and wear resistance at room temperature of the composite coating were examined by means of Microhardness Tester and Wear Tester, respectively. The results show that the main phases of the composite coating obtained by GTAW are ZrC, ZrB2 and alpha-Fe, ZrC exhibits hexahedron and petal shapes, ZrC-ZrB2 compound presents acicular and clubbed forms. With the increase of content of Zr+B4C, the maximum volume fraction of ZrC-ZrB2 particulates can reach 16.5%, microhardness is up to 1300HV, and wear resistance is about twenty times higher than that of AISI1020 steel substrate.