Investigation of the mechanical and corrosion behavior of Ni-P-W/h-BN composite coatings using the electric free coating method

This thesis describes the production and characterization of Ni-P-W/h-BN composite coatings by electroless coating method to improve the surface properties of 2024-T3 aluminum alloy. Electroless plating is a plating method that uses a chemical reaction to form thin films on metal surfaces without requiring electrical current. Ni-P-W/h-BN composite coatings are multi-component coatings consisting of nickel, phosphorus, tungsten and hexagonal boron nitride (h-BN) particles. These coatings offer superior mechanical and corrosion properties such as high hardness, wear resistance, corrosion resistance and coefficient of friction. In the thesis, the production of Ni-P-W/h-BN composite coatings with different h-BN concentrations on the surface of 2024-T3 aluminum alloy by electroless coating method is explained in detail. Properties of coatings such as morphology, microstructure, phase structure, hardness, wear behavior, corrosion behavior and friction coefficient have been examined by various analysis and test methods. In this context, coating parameters were chosen as pH, temperature, time, h-BN contribution rate and mixing speed of the plating bath. Coating thickness, coating hardness, coating structure, coating composition, and coating morphology were measured by micrometer, microhardness tester, X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM), respectively. Coating corrosion resistance was evaluated by potentiodynamic polarization test, and coating wear resistance was evaluated by dry friction test. As a result, it has been revealed that the electroless coating method significantly improves the mechanical and corrosion behaviors of Ni-P-W/h-BN composite coatings, and the coating performance increases further with the increase in the h-BN additive ratio. Coating thickness, coating hardness, corrosion resistance and wear resistance were found to be related to parameters such as pH, temperature, time, h-BN contribution rate and mixing speed of the plating bath. The coating structure, coating composition and coating morphology changed with the increase of h-BN additive ratio. As the h-BN contribution rate increased, more h-BN particles were seen in the coating, coating crystallinity decreased, the coating surface became smoother and the coating friction coefficient decreased. This study has shown that the electroless coating method is an effective method in the production of Ni-P-W/h-BN composite coatings and that these coatings can be used in industrial applications. Key Words : Electroless Plating, Ni-P, Ni-P-W/h-BN, Composite