A Comprehensive Experimental Study and Numerical Analysis of Coefficient of Friction of Nanocomposite Coatings.

Abstract

This paper presents a comprehensive study of nanocomposite coating friction behaviour in oscillating-reciprocating simulated condition with interfacing steel ball. A study on Nickel/Graphene (Ni/GPL) and pure Nickel (Ni) coatings has been conducted. Pre-test SEM, EDS and AFM analyses were performed to study the particle size, particle distribution, grain size and surface morphology of coatings. Furthermore, four types of tests were performed to compare the COF of pure Ni and Ni/GPL coatings subject to various test conditions. The post-tests revealed that Ni exhibited higher coefficient of friction (COF) compared to Ni/GPL which was evidenced by microscopic characterisation of wear tracks, wear on counter carbon steel ball and “U-shaped” wear depth profiles of wear tracks. The “U-shaped” profiles were utilised to calculate the energy distribution (Archard factor density) along the interface. A novel 2-D predictive numerical model integrating the wear concepts with the microstructural and lubrication concepts is developed to investigate the influences of intrinsic microstructural properties of nanocomposite coatings for instance porosity and surface stresses on COF. Predictions from newly developed model and the experimental results are in close agreement. In conclusion Ni/GPL showed better COF than Ni because of high strengthening properties in the presence of graphene. Although significant body of experimental research is available in terms of understanding frictional performance of various nanocomposite coatings, there is a need for the development of novel yet reliable predictive models to analyse the coefficient of friction (COF) of nanocomposite coatings within the context of design and industrial applications. The significance of this research is apparent from numerous applications which need precise modelling methods for predicting coatings failures owing to high COF and wear. The research will convey substantial impact to high-end manufacturing, renewable , automotive and aerospace industries in addressing several frictional failures.