Effect of Surface Melting and Chromium Surface Alloying on Wear Behavior of Ductile Iron

Tribological properties of ductile iron after surface melting and chromium surface alloying via pre-placing of ferrochromium powder and subsequently surface melting by tungsten inert gas process were investigated. The surface-treated samples were characterized using optical and scanning electron microscopes equipped with energy-dispersive x-ray spectroscopy, microhardness, and x-ray diffraction techniques. Wear behaviors of the treated samples were also studied by using a pin-on-disc machine. Surface melting and chromium surface alloying resulted in the formation of structures similar to those of the white cast iron and high chromium cast iron in the treated layers, respectively. The hardness of the surface-melted and alloyed layers was over 3 and 4 times higher than that of the base material, respectively. As a result, the wear rates of the surface-melted and alloyed layers reduced to less than 6 and 3% of that of the untreated ductile iron, respectively. The coefficient of friction was also significantly reduced after surface melting and alloying. The wear mechanisms were mainly oxidative for the surface-treated materials, while it was a combination of plastic deformation, adhesion, and oxidation for the case of as-received ductile iron.