Investigation of wear behavior of borided gear steels

In this study, GS 18NiMoCr36, GS 22NiMoCr56 and GS 32NiCrMo6.4 gear steels were subjected to boronizing at 950°C for 2 and 6 hours with EKabor-II boron powder. As a result of the experiments, the surface morphology of the boride layers formed on the steels was investigated by optical microscopy, their hardness values were measured by the micro-hardness device and the phases formed on the layer were determined by XRD technique. Wear tests were performed on a ball-disk wear instrument at 0.2, 0.3 and 0.4 m/s sliding speeds and load of 10 N, under dry conditions and at room temperature. The surface roughness and wear volumes of the steels were calculated using Taylor-Hobson Rugosimeter device.As a result of XRD analysis, it was detected that FeB, Fe2B, CrB and Cr2B phases were formed on the boride layers. As a result of the boronizing process performed on the steels, it was observed that boride layer thickness increased with the increase in the boriding time. In addition, it was detected that the boride layer thickness varied according to the chemical composition of the steels. Boriding process increased the surface hardness of the steels approximately 5-fold. As a result of wear tests, the wear rates of the gear steels were observed to decrease with an increase in the boriding time. In addition, a decrease was observed in wear rates with the increase in the sliding speed.