Microstructures and wear properties of various clad layers of the Fe–W–C–B–Cr system

In this study, using the gas tungsten arc welding method, various hard boride and carbide phases inside clad layers were synthesized in situ from Fe, C and Cr-containing SKD61 or SKD11 substrates spread over with tungsten boride powder. According to the results concerning hardness and microstructures, the clad layers of the Fe–W–C–B–Cr system had a high hardness because of the precipitation hardening of various precipitates. Additionally, the high C and Cr content of WB-SKD11 specimens led to clad layers with hard and complicated structure. The clad layers of the Fe–W–C–B–Cr system were quite thick, with a mean thickness of 6 mm. By observing scanning electron microscopic images, it was evident that the soft regions in the heat-affected zones of the WB-SKD11 specimen had a bainite and retained austenite structure that was due to the high C and Cr content in the substrate. However, the WB-SKD61 specimen had no soft regions; its heat-affected zone was only composed of a martensite structure. The hardness of the WB-SKD61 specimen gradually decreased along the direction deep into the clad surfaces. The WB-SKD11 specimen was treated with cryogenic treatment that could reduce some of the retained austenite structures and significantly improve the hardness of the heat-affected zone. During the dry sliding wear test, the hard vein-shaped phase in the WB-SKD11 clad layers provided strong mechanical interlocking. Therefore, the wear performance of the WB-SKD11 clad layers was substantially better than that of the other specimens under all test conditions in this study.