Synthesis and characterization of Ni-TiO2 composite coatings by electro-co-deposition

Abstract

Ultrafine TiO2 dispersed nickel composite coatings have been prepared by direct current deposition process on steel substrate from Watt's bath 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 was applied during deposition with prior ultrasonic agitation. For de-agglomeration, Hexa decylpyridinium bromide (HPB) was used in varying quantity in plating bath as surfactant. 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. Selective amount of HPB addition produces hard orientation of nickel in the composite coating along with better TiO2 co-deposition rate leading to higher microhardness and wear resistance. Wear is mainly adhesive in nature and the worn out TiO2 particles shift it nominally to abrasive mechanism.