Microstructure and cavitation damage characteristics of surface treated gray cast iron by plasma ion nitriding

Abstract

In this study, plasma ion nitriding (PIN) was performed as a measure to prevent the cavitation damage of gray cast iron (GCI) which is a cylinder liner material of diesel engine and evaluated its applicability. GCI treated by PIN presented about 45.2% improvement in surface hardness. In addition, a thickness growth behavior of flake-shaped graphite was observed in the nitrogen diffusion layer. As a result of cavitation erosion test, the maximum surface damage depth increased greatly due to a crater growth behavior along the depth on the flake-shaped graphite distributed on the surface. Furthermore, the weight loss after cavitation test indicated poorer cavitation resistance compared to the as-received specimen. Consequently, the application of PIN to prevent the cavitation erosion damage of GCI requires minimization of defects by flake-shaped graphite.