Tribological behaviour of enamel coatings

An experimental study has been carried out to evaluate the tribological and mechanical properties of steel hardened with glass-ceramic enamel under ambient conditions. Three types of borosilicate based enamels were fused onto mild steel by the firing process, after a sandblasting and a ground coat to ensure surface integrity between the substrate and the covering coat. The surface roughness, micro hardness, wear track and tribological characteristics of the enamel coating were then characterised by an atomic force microscopy, a Vicker micro-hardness tester, a 3D optical profiler, an EDS/SEM, and a friction and wear testing tribology meter. The tribological differentials of these top coats were examined after sliding against chrome steel, zirconia and silicon nitride. The worn morphologies provided some understandings of the failing mechanism due to friction. During dry sliding with a silicon nitride mating part, the coefficient of friction and loss of enamel enriched with titanium was less than the chrome steel balls, although the zirconia ball succumbed to serious wear. The changes in the worn morphologies and chemical composition under different sliding contacts, and the corresponding wear mechanism were observed, with abrasive wear being dominant.