Abstract

Thermally sprayed tribological coatings are extensively employed in aerospace applications to address critical issues including corrosion, erosion, oxidation, abrasive wear, and fatigue under different service conditions. Besides addressing these difficulties, these coatings are essential for improving the efficiency of gas turbine engines, thereby decreasing fuel consumption and emissions.
High Velocity Air-Fuel (HVAF) thermal spraying has become a promising method for producing carbide-based tribological coatings, offering significant advantages over other techniques such as Air Plasma Spray (APS) process. Its higher particle velocity and lower flame temperature result in denser coatings with reduced oxide content and enhanced hardness. These properties make HVAF an ideal method for developing advanced coatings that can effectively resist surface degradation caused by wear, corrosion, and erosion, even under extreme temperatures.
The objective of our research work is to investigate the tribological properties of thermally sprayed carbide-based coatings deposited by plasma spray and high velocity air fuel deposition processes. This work consists of two research studies, the first emphasize the influence of deposition processes (i.e., APS and HVAF) and binder content (i.e., pure carbide and cemented carbide) on the microstructural, mechanical, and tribological behavior of chromium carbide-based coatings at room temperature and 450 °C. The second study is a preliminary work that evaluates the microstructure of pure silicon carbide coatings deposited by suspension plasma spraying process.
The tribological test was performed using a ball-on-flat tribometer and the wear profiles were obtained using a laser confocal microscope. The Ex-situ characterization of the as-deposited coatings were performed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), image analysis, and the Vickers microhardness test was performed on the cross-sections of the coatings at room temperature. The HVAF sprayed Cr₃C₂-25NiCr coating deposited with the 4L4 nozzle exhibits the lowest friction and improved wear resistance compared to all the tested APS coatings at room temperature and 450°C. Moreover, the second study has demonstrated that pure SiC coatings can be produced using suspension plasma spray (SPS) process and open pathway for future development of ceramic materials which are prone to decomposition.