Investigation on Tribological Characteristics of Plasma Transferred Arc Cladded Co-TiC-CaF2 Metal Matrix Composite Coating Produced on Magnesium Alloy AZ91D Substrate

The demand for lightweight materials with enhanced mechanical and wear-resistance properties has spurred significant research in the field of surface modification of magnesium alloys. In this work, Co-TiC-CaF₂ metal matrix composite (MMC) coating has been produced on magnesium alloy AZ91D substrate by plasma transferred arc (PTA) coating process. The effect of scan speed, PTA current, and CaF₂ content on microhardness, coefficient of friction (COF), and wear rate of Co-TiC-CaF₂ coating have been studied. The x-ray diffraction, SEM, and energy-dispersive x-ray spectrometry (EDS) have been used to determine the phases, morphology of the coated surface, and chemical elements. The findings revealed that the coatings are compact and uniform with some microcracks and voids, with Co, TiC, and CaF₂ particles evenly distributed and metallurgically bonded to the substrate. Under optimal parameters, Co-TiC-CaF₂ composite coating exhibits maximum average microhardness value of 958 HV_0.05, compared to 68 HV_0.05 of Mg alloy AZ91D substrate. This exhibits that the clad layer offers 14 times greater hardness than the magnesium alloy AZ91D substrate. The wear rate of Co-TiC-CaF₂ MMC composite coating was measured as 2.05 × 10^-8 g/N-m, while wear rate of the substrate AZ91D Mg was 79.23 × 10^-8 g/N-m. Therefore, the coating has 38 times more wear resistance than Mg alloy AZ91D substrate. Comparison to substrate, sample CTC-10 exhibits smooth worn surface and lower COF. This comprehensive study offers valuable information on developing advanced surface coatings for magnesium alloys. Hence, lightweight materials with improved tribological performance can be used in the industries which require lightweight of the engineering components.