Improved Wear Resistance of Austempered Gray Cast Iron Using Shot-Peening Treatment

In this research, ball-on-plate reciprocating sliding wear tests were utilized on austempered and quench-tempered gray cast iron samples with and without shot-peening treatment. The wear volume loss of the gray cast iron samples with different heat treatment designs was compared under equivalent hardness. The phase transformation in the matrix was studied using metallurgical evaluation and hardness measurement. It was found that thin needle-like ferrite became coarse gradually with increasing austempering temperature and was converted into feather-like shape when using the austempering temperatures of 399°C (750°F). The residual stress on the surface and sub-surface before and after shot-peening treatment was analyzed using x-ray diffraction. Compressive residual stress was produced after shot-peening treatment and showed an increasing trend with austempering temperature. In sliding wear tests, austempered gray cast iron had lower wear volume loss than quench-tempered gray cast iron before and after shot-peening treatment. The wear tracks were examined using scanning electron microscopy. Delamination and smearing were the main wear mechanisms on the gray cast iron samples.