Abstract
The tribological performance of a nanocrystalline coating is heavily influenced by its composition, morphology, and microstructural characteristics. This research work describes the effect of heat treatment temperature on the microstructural, morphological, and mechanical behavior of nanocrystalline Ni/TiO2 coatings produced by electrophoresis. The surface morphology and coating cross section were characterized by scanning electron microscopy (SEM). The composition of coatings and the percentage of TiO2 nanoparticles incorporated in the Ni matrix were studied and estimated by using an energy-dispersive spectroscopic (EDS) analysis, while x-ray diffractometry (XRD) was used to investigate the effect of heat treatment temperature on phase structure. The results showed agglomeration of TiO2 nanoparticles on the surface of the coating. The high hardness and wear resistance recorded for the as-deposited coating was attributed to the uniform distribution of TiO2 nanoparticle clusters throughout the cross section of the coating. Heat treatment of the Ni/TiO2 coatings to temperatures above 200 °C led to significant grain growth that changed the surface morphology of the coating and reduced the strengthening effects of the nanoparticles, thus causing a reduction in the hardness and wear resistance of the coatings.
Highlights
Nanostructured cermet coatings have been the focus of several recent studies, because of the possibilities of producing materials with exceptional physical and chemical properties such as superior mechanical, chemical, and tribological properties
This study evaluates the effects of heat treatment temperature on the properties of nanocrystalline Ni/TiO2 coatings and permits a clear understanding of the impact of heat treatment temperature on the strengthening behavior of nanosized TiO2 reinforcements embedded into the coatings
It is evident that embedding TiO2 nanoparticles into the coating changes the surface morphology when compared to the smooth surface characteristic of pure nickel coating discussed in previous studies [14]
Summary
Nanostructured cermet coatings have been the focus of several recent studies, because of the possibilities of producing materials with exceptional physical and chemical properties such as superior mechanical, chemical, and tribological properties. There are several techniques capable of producing nanostructured coatings with the required wear and corrosion resistance. The inclusion of the ceramic particles in the coating and the uniformity of particle distribution are critical to achieving wear-resistant coatings [15,16,17,18,19]. The volume of the particles embedded in the coating is dependent on the concentration of ceramic particles suspended in the solution; as particle concentration in the solution increases, the volume of particles embedded in the coating increases. Other factors such as surfactant concentration and zeta
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