Investigation of tribological behaviour and diffusion model of Fe2B layer formed by pack-boriding on SAE 1020 steel

In this study, a substitute boriding powder including boric acid as boron source was prepared and employed for boronizing of SAE 1020 steel. The boronizing processes were performed at 850, 900 and 950 °C for 4, 8 and 12 h. The formed boride layers were identified by varied experimental methods such as optical microscope, SEM and WDS analysis. As an outcome of the analyses, the boride layer containing only Fe2B phase with saw-tooth morphology was specified on surface of the samples. A diffusion model was proposed to estimate the coefficients of boron diffusion in the Fe2B layers. The value of boron activation energy for SAE 1020 steel was calculated as 183.14 kJ/mol and the result was contrasted with literature data. As a result of the microhardness measurements, the average hardness value of Fe2B layer was about between 1200 and 2000 HV0.1. The average hardness values of the transition zone and matrix zone were determined to be approximately 160 HV0.1 and 151 HV0.1, respectively. This study mainly concentrates on the tribological properties of borided SAE 1020 steel with using alternative boriding powder. Coefficient of friction graph was drawn for each sample and the wear rates were calculated. It was specified that specific wear rate of borided samples was roughly 47 times lower than that of unborided samples. © 2019 Elsevier B.V