MICROSTRUCTURE AND MECHANICAL PROPERTIES OF WIRE ARC ADDITIVE-MANUFACTURING HIGH-CARBON CHROMIUM BEARING STEEL

Wire arc additive-manufacturing technology (WAAM) was conducted successfully on a high-carbon chromium bearing steel with an ER55-Ni welding wire and a GCr18Mo substrate. It is found that the microstructure of the cross-section of the WAAM sample is divided into three parts, i.e., the deposition layer, the transition layer and the substrate. The microstructure of the deposition layer mainly consists of needle-like tempered martensite and cementite, with a small quantity of ferrite. The transition zone is composed of coarse bainite and ferrite. In the deposition layer, the hardness gradually decreases from the top to the root, and the hardness of the transition layer is close to 350 HV. The arc-cladding sample exhibits a higher yield strength and tensile strength but lower elongation than the substrate sample. The necking is formed and a failure occurs at the transition layer of the WAAM sample. The maximum depth values of wear scars on WAAM and substrate samples are close to each other. The wear is more uniform on the WAAM sample but the cross-sectional area of its wear scar is larger than that of the substrate sample. The wear resistance of the WAAM sample is lower than that the substrate sample, which is mainly attributed to the low hardness of the WAAM sample.