An Investigation on Room and High Temperature Wear Performance of Fe-45WC Hardfaced Coating Applied on Ductile Cast Iron

摘要

In this study, Fe-45WC hardfacing coating was applied using flux core welding wire on ductile cast iron substrate by the GTAW process. Microstructural characterization and wear performance measurements were performed at room and 400 degrees C. The matrix phase of the hardfaced coating contained dendrites that chemically contained Fe and other elements such as Ni and Cr, diffused from the buffer layer. In the inter-dendritic spaces, tungsten-rich Eta carbides (Fe3W3C) with fish-bone morphology as well as chromium-rich carbides (Cr7C3) with leaf-shaped morphology were observed. The formation of eta-carbide was due to the dissolution of WC particles during the thermal effect of the hardfacing process, and the formation of Chromium carbide was caused by dilution of the chromium element from the buffer layer. For the room temperature wear test, a protective tribolayer was formed on the wear track due to the presence of graphite in ductile cast iron, which acted as a lubricant. However, this tribolayer was unable to protect the cast iron, and it was removed during the wear test at room temperature because of its low adhesion, leading to severe wear of the base metal. On the other hand, for the Fe-45 WC hardfaced coating, despite the lack of formation of the lubricant at room temperature, much better wear resistance was observed as compared to the base metal, mainly due to its higher hardness and also presence of WC reinforcing particles in its structure. For the high temperature wear test at 400 degrees C, due to the formation of a continuous tribolayer, with good adhesion on the wear track of base metal and hardfaced coating, higher hardness, and trapping of WC debris in the tribolayer for the Fe-45WC hardfaced cast iron, much better wear resistance in comparison to the room temperature wear test was observed.