Visualization of Wear Process between FCD Cast Iron and Copper Alloy Using One Direction Rotary In-situ Friction State Visualization Tester

In this study, a friction test was conducted on cast iron and copper alloys using a friction state visualization tester capable of in-situ observation. The results of the friction coefficient, the in-situ observation, and the analysis of the cast iron surface by SEM and EDS were combined to visualize the seizure behavior. In this test, copper alloy powder, which simulates wear debris, was mixed into the friction track under poor lubrication to create a severe sliding condition like the actual hydraulic motor. In-situ observation enables the behavior of wear debris on the cast iron surface and the process of seizure to be observed. When seizure occurs, the friction coefficient increases, copper alloy is repeatedly transferred to the cast iron surface and embedded in and desorbed from the graphite, and the copper alloy surface shows metallic luster and its area is expanded. When seizure occurs, the coefficient of friction increases, the copper alloy repeatedly migrates to the cast iron surface, embeds in graphite, and detaches from graphite, resulting in a metallic luster on the copper alloy surface, which is enlarged in area. In addition, the ferrite structure around the graphite is embrittled and crushed by nitriding, which promotes seizure at the newborn surface.