The effect of TiO2 concentration on microstructure, corrosion behavior and wear behavior of Ni-P-W-TiO2 coating

Nickel-phosphorus coatings (Ni-P) are widely used in industry due to their high hardness, corrosion resistance and very good mechanical and chemical properties. Oxide particles such as TiO2 can be used to increase the wear resistance of these coatings. In this study, the Ni-P-W-TiO2 composite coating was deposited on the AISI 304L steel substrate using the electroplating method. Electroplating was performed at concentrations of 10, 20, and 30 g/L TiO2, and the effect of TiO2 concentrations on the microstructure, corrosion behavior, and wear behavior was investigated. Coatings were characterized by scanning electron microscopy (SEM). In order to investigate corrosion resistance, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests were used in 3.5% NaCl aqueous solution. A pin on disk test was used to test the wear resistance of uncoated and coated samples. Sample micro-hardness was also measured by the Vickers hardness test. Examination of the microstructure showed that the best TiO2 concentration for deposition was 20 g/L. The results of Tafel and electrochemical impedance spectroscopy tests were also consistent with microscopic images, and the results showed that the coating formed at concentration of 20 g/L had the highest corrosion resistance compared to other coated and non-coated samples. Also, the results of the wear test showed that increasing the TiO2 concentration increases the micro-hardness and wear resistance.