Effect of HVOF parameter on titanium oxide (TiO2) coating characteristics on AZ81 magnesium alloy

High-velocity oxy-fuel (HVOF) coating to enhance the erosion, wear, and corrosion-resistant properties crucial for orthopedic applications. HVOF is distinguished for its capability to provide surfaces with a dense and superior finish. Porosity and hardness serve as vital process variables in assessing performance. This current study aims to optimize HVOF process parameters to minimize porosity values in titanium oxide (TiO2) coatings applied on AZ81 magnesium substrate. Oxygen flow, liquefied petroleum gas (LPG) flow, coating material feed rate, and spray distance were selected due to their significant impact on the coating quality. Statistical techniques such as response surface methodology (RSM), analysis of variations, and design of experiments (DoE) were employed to obtain the necessary results. The findings indicate that LPG flow has the most significant influence on coating quality, followed by standoff distance, oxygen flow rate, and feed rate. The coating obtained using optimal spray parameters exhibits a lower surface porosity of 0.86 vol.% and achieves a greater hardness of 922 HV. This has been confirmed through validation via the response graph. Consequently, the optimized parameters for TiO2 deposit entail an oxygen flow rate of 266 lpm, an LPG flow rate of 68 lpm, a powder feed rate of 35 g/min, and a spray distance of 236 mm. KEY WORDS: High-velocity oxy-fuel, Response surface methodology, Porosity, Hardness, AZ81 Magnesium alloy, Titanium oxide Bull. Chem. Soc. Ethiop. 2024, 38(6), 1869-1886. DOI: https://dx.doi.org/10.4314/bcse.v38i6.28