ENHANCED TRIBOLOGICAL, MECHANICAL AND CORROSION PERFORMANCE OF MO AND NICR COATINGS ON LMD TI6AL4V ALLOY DEPOSITED VIA ATMOSPHERIC PLASMA SPRAYING IN A SELF -GOVERNMENT- DEVELOPED TECHNOLOGIES

Povzetek

In this study, Ti-6Al-4V (Grade 5) alloy components were fabricated via Laser Metal Deposition (LMD) and subsequently coated with Nickel-Chromium (NiCr 80/20) and Molybdenum (Mo) powders using Atmospheric Plasma Spray (APS) to enhance their surface durability. The objective was to evaluate the synergistic effects of LMD and plasma spray coatings on the mechanical, tribological and corrosion properties of the Ti alloy. Microstructural and chemical analyses using SEM and EDS confirmed dense, uniform coatings with strong metallurgical bonding and minimal porosity. Atomic Force Microscopy (AFM) revealed refined surface topographies, with Mo-coated samples exhibiting smoother profiles (Ra = 0.42 µm) compared to NiCr (Ra = 0.51 µm), facilitating better tribological contact. Vickers microhardness tests indicated significant surface strengthening, with hardness values increasing from 368 HV (uncoated) to 584.67 HV (Mo) and 537.66 HV (NiCr). Dry sliding wear tests demonstrated that Mo coatings provided superior wear resistance, with the lowest coefficient of friction (0.32) and specific wear rate (0.5 × 10⁻⁴ mm³/Nm), attributed to the formation of MoO₃ tribolayers. Electrochemical corrosion testing in 3.5% NaCl solution revealed that NiCr coatings outperformed Mo in corrosion protection, exhibiting a more noble corrosion potential (–450 mV) and significantly reduced current density (1.2 × 10⁻⁷ mA/cm²) due to the formation of a stable Cr₂O₃ passive film. These findings establish that integrating LMD with tailored plasma spray coatings enables surface-functionalized Ti alloys suitable for high-performance applications requiring enhanced wear and corrosion resistance.