Effects of thermal and thermomechanical treatments on sliding wear of graphite crystallized white cast iron
The effects of thermal and thermomechanical treatments on sliding wear of graphite crystallised white cast iron (GWCI) were studied. Due to the inherent embrittlement of GWCI, a laminated metal in which the GWCI is cladded by low carbon steel was prepared for this study. Three cylindrical samples (GWCI-A, GWCI-B and GWCI-C) were machined from the same laminate. GWCI-A was kept in as-cast state while GWCI-B and GWCI-C underwent the thermal and thermomechanical treatments, respectively. The pin-on-disc type sliding wear tests were performed on the GWCI layers at room temperature. The microstructures and wear mechanisms were analysed by optical microscope, scanning electron microscope and the Vickers hardness test. Experimental results demonstrated that the GWCI, after laminating with ductile steel, can be deformed at high temperature with crack-free. The thermomechanical treatment produced a finer microstructure and crushed primary carbides in GWCI-C. Both GWCI-B and GWCI-C displayed plenty of secondary carbides in supercooled austenitic matrix, which was more favourable to squeeze the graphite and form the oxide layers than the matrix of martensite plus retained austenite in GWCI-A. The wear resistance of GWCI-C was superior to that of GWCI-A and GWCI-B because the oxidational wear rather than delamination dominated the sliding wear process.