Synthesis and Characterization of Nano-TiO2 Dispersed Composite Coating by Electro-co-deposition

Abstract

Nano-TiO2 dispersed Nickel composite coatings have been prepared by direct current deposition process on steel substrate from Watt’s solution to improve the surface mechanical property of conventional nickel coating. To resist agglomeration of ultra fine particles in plating bath due to high surface free energy and to get homogeneous coating, magnetic stirring and ultrasonic agitations were used along with surfactant addition. Characterization of TiO2 powder as well as microstructure, hardness and wear properties of the coatings were studied by means of XRD, SEM, microhardness tester and ball-on-plate type wear tester. TiO2 incorporation in the coatings was uniform and dispersion of TiO2 was below 100 nm size along with the faceted nickel matrix with a coating thickness of about 33 micron. Systematic and sharp increase in surface microhardness was observed after incorporation of TiO2 powder. Maximum microhardness HV0.05 647 of composite coating was achieved compared to HV0.05 375 of pure Nickel coating. The increase in wear resistance was also sharp after incorporation of TiO2 along with little shift from adhesive to abrasive wear regime leading to maximum ten times decrease in penetration rate. Effect of surfactant added in plating bath on different properties and microstructure of the coating was also studied. Dispersion strengthening, texturing effect and ultrafine matrix structure lead to improvement of surface mechanical properties of the coating.