FABRICATION AND INTERFACIAL STRUCTURE OF TiC-Fe CERMET GRADED COMPOSITE COATING ON CAST STEEL SUBSTRATE BASED ON SHS TECHNOLOGY

A Ti-C-Fe preform was pre-placed in a mould cavity and then was directly ignited to bring about the self-propagating high-temperature synthesis (SHS) reaction by the temperature of pouring liquid carbon steel. As a result, a TiC-Fe cermet coating with a thickness of 10 mm was simultaneously synthesized on the steel substrate during its casting. The phase constituents of the synthesized coating were inspected by X-ray diffraction (XRD), and the microstructure of the coating, especially its interfacial structure with the substrate, was analyzed with optical microscopy (OM), scanning electron microscopy (SEM) and electron probe microanalyzer (EPMA). The experimental results show that the coating, except for its outside layer with about 2 mm thickness, has dense microstructure. The amount and size of the synthesized TiC particles in the coating decrease gradually in the thickness direction, so that a graded composite interface is formed between the coating and the substrate. It is considered that the infiltrations of the poured liquid steel into the preform and the fusion of Fe powders in the preform may make a contribution to the formation of the graded composite coating.