Electrode material selection for repairing 42CrMo bearing steel by electric spark deposition

To explore the remanufacturing technology for large bearing parts, this study conducted electric spark deposition (ESD) test using 42CrMo bearing steel as the substrate, and 42CrMo steel, high-speed steel (HSS), Inconel 625 alloy, WC-15TiC-6Co, and WC-10Co as electrodes respectively. The influence of different electrode materials on the formation of deposited layers was analyzed, and the coating material suitable for repairing 42CrMo bearing steel was optimized with deposition efficiency, compactness, wear resistance, and microhardness of the deposited layer surface as indicators. The results show that under the same deposition test conditions, the lower the melting point of electrode materials, the larger the area of deposition spots, and the higher the material transfer efficiency and compactness of the deposited layer. Additionally, the properties of the electrode material have a direct impact on the formation of the deposited layer. Among them, for the high-melting-point WC-15TiC-6Co and WC-10Co electrodes, the microhardness of their deposited layers can both reach over 1200 HV, however, their deposition thickness is both less than 40 µm, and the deposited layers are cracked. In contrast, Inconel 625 exhibits relatively high deposition efficiency due to its low melting point, and its deposited layer has high compactness, but the microhardness is 360 HV. The microhardness of the HSS deposited layer is 667 HV, and its wear resistance is 2.4 times that of the substrate. It also possesses relatively high deposition efficiency. For the 42CrMo electrode, which is of the same material as the substrate, both the wear resistance and microhardness of its deposited layer are basically the same as those of the substrate. Therefore, WC-15TiC-6Co and WC-10Co are not suitable as coating materials, while Inconel 625 can be used as the bottom filling material, and both 42CrMo and HSS are applicable as repair materials for the surface of 42CrMo bearing steel.