Surface Modification of Cast Iron Containing 6 mass% Aluminum and Its Wear Property

Flake graphite cast iron containing aluminum is known to have excellent heat resistance. In this research, the characteristics of a surface modification process and the wear property of surface-modified aluminum alloyed cast iron were investigated. When flake graphite cast iron containing 6 mass% aluminum was heat-treated at 1273 K in air, alumina precipitated at the positions where graphite existed, showing the same shape as flake graphite. The thickness of the alumina dispersed layer reached about 1 mm by heat-treating for more than 72 ks at 1273 K. This material was evaluated by the pin-on-disc method, and showed excellent wear property compared to normal flake graphite cast iron. The surface-modified layer showed excellent wear resistance especially at a test speed of 1.0 m/s. Also, at a test speed of 0.1-0.5 m/s, this layer showed better wear resistance than normal cast iron. Apparently the material surface transforms into an oxidized wear state due to the adhesion of oxides including alumina, resulting in improved wear resistance. This is a new surface modification method applying decarburization of graphite and the easy oxidation feature of aluminum. The method is easy to perform as it uses only heat-treatment in air, and suggests that cast iron having new characteristics may be created by substituting other substances for the included graphite.