Effects of microstructures on the abrasive wear behaviour of spheroidal cast iron

Martensite spheroidal cast iron is an abrasion-resistant material of superior toughness to white case irons. In order to assess the effects of matrix and graphite phases on the wear performance of the iron, abrasion tests were carried out under both two-body (pin-on-disc) and three-body impact conditions. The matrices involved in the tests included martensite, martensite with increased retained austenite, and bainite. The effect of graphite was investigated by introducing an high carbon steel which has similar microstructures to the matrices of the tested iron. The wear mechanisms were analysed by means of worn surface and subsurface observations with a scanning electronic microscope and an optical microscope. The two-body abrasive wear of the tested iron and steel was demonstrated with microcutting and ploughing processes. When impacting loads were introduced, severe plastic deformation occurred on the worn surface layers of specimens especially on the bainitic specimens. The graphite phase was found to be worn rapidly on worn surface and seriously deformed beneath the worn surface. A number of cracks initiated at the graphite-matrix boundaries were also found on the subsurface of three-body impact worn irons. The wear resistances of the martensite structure have been estimated to be higher than those of the bainite structure. As the residual austenite was increased by raising the austenizing temperature, the tested iron and steel became more wear resistant. The destructive effect of the graphite phase on the wear resistance of spheroidal cast iron was determined to depend on the abrasion conditions. Under two-body abrasion, the effect of graphite was found to be less, as measured by the lower wear losses of the tested iron and steel. However, as soon as an impacting load was introduced, the wear resistance of the iron decreased owing to the existence of the graphite phase. © 1995.