Tribological Performance Assessment of Abradable Powder Coated Pistons Considering Piston Skirt Geometry and Surface Topography

Surface coatings are one of the most widely used routes to enhance the tribological properties of cylinder kits due to effective sealing capability with low friction coefficient and high wear resistance. In the current study, we have conducted the surface texture characterization of the coating on piston skirts and evaluated the impact of a novel Abradable Powder Coating (APC) on cylinder-kit performance in comparison to stock pistons. The surface texture and characteristic properties varying across the piston skirt are obtained and analyzed via a 3D optical profiler and OmniSurf3D software. The engine operating conditions are found through a combination of measurements, testing, and a calibrated GT-Power model. The variable surface properties along with other dimensions, thermodynamic attributes, flow characteristics and material properties are used to build a model in CASE (Cylinder-kit Analysis System for Engines)- PISTON for both an APC coated piston and a stock piston. The surface texture analysis shows that the APC coating resembles a group of mushroom cap structures. The APC coated surface has a higher number of deeper valleys than the stock coated surface; these valleys would potentially be beneficial for lubrication and oil retention. Comparison of different performance parameters from CASE simulation results shows higher minimum oil film thickness and lower hydrodynamic shear force on the APC coated piston. The APC coated piston is predicted to experience less tilting as well as secondary motion than the stock piston. All these features are believed to make the APC coating a suitable candidate for piston skirt coating.