Wear behaviour of plasma paste boronized of AISI 8620 steel with borax and B2O3 paste mixtures

Abstract

In the present study, AISI 8620 steel was plasma paste boronized (PPB) by using paste mixtures with different borax and B2O3 percentages. The PPB process was carried out in a DC plasma system at 973, 1023 and 1073 K for 5 h in a gas mixture with 70% H2–30% Ar under a constant pressure of 103 Pa (10 mbar). The thickness of boride layers ranged from 15.9 to 53.6 μm depending on the temperature and process time. The hardness of the borides formed on the surface of the steel substrate and unborided steel substrate were 1648–1924 HV0.05 and 226 HV0.05, respectively. X-ray diffraction analysis of the boride layers on the surface of the samples were obtained for FeB and Fe2B phases. The wear tests on the steel were performed by using a ball-on-disc test device at room temperature with applied load of 10 N and with a shear velocity of 0.2 m/s. Wear test results showed that the highest value of wear rate was observed in the unborided sample while the lowest wear rate was observed in the PPB samples with 30% borax + 70% B4C paste at 1073 K for 5 h.