Experimental investigation on the wear characteristics of TiC−Co composite coating deposited on AZ91D Mg alloy substrate by plasma transferred arc (PTA) welding process

Abstract

In this investigation, a plasma transferred arc (PTA) cladding process was employed to deposit TiC-Co composite coatings on substrate of AZ91D magnesium (Mg) alloy. The morphology and phases of the recently produced composite coatings were examined using scanning electron microscopy (SEM) and X-ray diffractometry (XRD). The microhardness and wear rate were evaluated by Vickers microhardness tester and pin-on-disc wear and friction test apparatus at the room temperature respectively. The results demonstrate that dense, uniform, and crack free coatings, with good metallurgical bonding to the AZ91D Mg alloy substrate were formed. The most of the phases present in composite coatings were TiC, Mg, CoTi, α-Co, AlCo, Al3Ti, and Co3C. The maximum average micro-hardness of TiC-Co composite coating was found to be about 1743 HV, which depends on the PTA currents. Whereas, average micro-hardness of the AZ91D Mg alloy substrate was 65 HV. This indicates that the coated layer produced increase in hardness about 27 times of substrate hardness. The cladding layer exhibited a wear rate of 4.94×10-8 g/N-m, whereas the wear rate of the AZ91D Mg alloy substrate was 58×10-8 g/N-m. This indicates that the wear resistance of cladding layer was 12 times higher as compared to AZ91D Mg alloy substrate. The enhanced micro-hardness and wear resistance of TiC-Co composite coating can be attributed due to the formation of ceramic and intermetallic compounds, unveiling its superiority over the AZ91D substrate.