Surface Characterization and Boriding of Nickel and Cobalt Alloys

In this work, Cobalt-Magnesium (93% Co–7% Mg; CM) and Nickel-Magnesium (93% Ni–7% Mg; NM) alloys were successfully borided by pack boriding at the temperature range of 900°C for 1.5 and 4.5 h. The characteristics of boride layers were examined by X-ray diffraction, scanning electron microscopy, surface roughness, density and microhardness tester. After boronizing, the major dominant phase were found to be NiB for NM alloys and Co2B for CM alloys. Boride coating resulted in smooth and dense feature confirmed by SEM. The thickness of boride layer varied from 47.96 to 145.21 μm for CM alloy and 67.21 to 179.84 μm for NM alloy depending on the process time. Boride layer has a hardness varied from 1752 to 1865 HV0.05 for CM alloy and 1634 to 1768 HV0.05 for NM alloy, whereas the Vickers hardness value of the untreated Cobalt and Nickel were 194 HV0.05 and 118 HV0.05 respectively. CoxOy, NixOy and MgxOy phases were formed as a result of EDX analysis after the wear test.