Tribological properties and characterization of borided Co–Mg alloys

Abstract

In this study, tribological properties and characterization of borided Co–Mg alloys were investigated. Cobalt–magnesium (CM) alloys with 97% Co–3% Mg composition were borided at temperatures of 850–900°C and for 1.5–4.5 h with solid boriding. The properties of the resulting boride layers were measured and determined by microhardness, scanning electron microscopy (SEM), X-ray diffraction (XRD), density, and surface roughness testers. XRD analysis results after boriding found CoB, Co2B, and Co phases. Depending on the boriding time and temperature, the thickness of the boride layer for the CM alloy varied from 51 to 138 µm. The boride layer had a hardness varying between 1,674 and 1,956 HV0.05 for the CM alloy, while the Vickers hardness value of untreated Cobalt was 52 HV0.05. The wear tests were carried out in a ball-disc arrangement under a dry friction condition at room temperature with an applied load of 10 N and with a sliding speed of 0.3 m/s at a sliding distance of 250 m. It was observed that the wear rate of borided and unborided CM alloy ranged from 25.89 × 10−5 to 94.95 × 10−5 mm3/N m. As a consequence of the findings, the author reported that boriding CM alloys in the given conditions can make a difference for different application areas.