Tribological Performance of HVOF-Sprayed CuNiIn Coating for Aerospace Bearing Application

Lead-based bearing materials are widely used in aerospace engines due to their excellent lubricity and resistance to seizure. However, the toxicity of lead poses significant environmental and health concerns, encouraging the development of lead-free alternatives. In this study, the tribological performance of CuNiIn coatings, deposited by High Velocity Oxygen Fuel (HVOF) spraying was investigated as a potential alternative for conventional lead-based bearing materials. HVOF deposition allows the formation of dense and hard coatings with minimal oxidation and strong adhesion to the substrate. The deposited coatings showed a uniform thickness of approximately 400 µm. Microstructural characteristics and mechanical properties were evaluated through SEM analysis and microhardness measurement. Dry sliding tribological tests were performed using an Anton Paar tribometer at a constant load of 5 N under room temperature and elevated temperature (400 ºF) conditions. The results showed that the CuNiIn coating exhibited a stable coefficient of friction of approximately 0.85 at room temperature, while at 400 ºF the friction coefficient initially increased during running-in stage and gradually decreased to ~ 0.70 during steady-state sliding. Wear depth profiles showed a maximum wear depth of ~ 210 µm at room temperature and ~ 158 µm at 400 ºF, indicating reduced wear at elevated temperature. The low friction and wear at elevated temperature were due to the formation of thermally induced tribo-layers that lower interfacial shear resistance.