Tribological Evaluation of a UHMWPE Hybrid Nanocomposite Coating Reinforced With Nanoclay and Carbon Nanotubes Under Dry Conditions

Abstract

A novel hybrid polymer nanocomposite coating of ultrahigh molecular weight polyethylene (UHMWPE) reinforced with nanoclay (C15A) and carbon nanotubes (CNTs) has been developed to protect metallic mating surfaces in tribological applications. The hybrid nanocomposite coatings were deposited on aluminum substrates using an electrostatic spraying technique. Ball-on-disk wear tests using a 440C stainless steel ball as the counterface were conducted on the coatings under dry conditions to determine the optimum amount of the loadings of the nanofillers and evaluate their tribological performance at different normal loads and linear velocities. Micro-indentation, raman spectroscopy, scanning electron microscopy (SEM), and optical profilometry techniques were used to characterize the coatings in terms of hardness, dispersion of the nanofillers, morphology, and wear mechanisms, respectively. Results showed that the UHMWPE hybrid nanocomposite coating reinforced with 1.5 wt % of C15A nanoclay and 1.5 wt % of CNTs did not fail even until 100,000 cycles at a normal load of 12 N and a linear speed of 0.1 m/s showing a significant improvement in wear resistance as compared to all other coatings evaluated in this study.

UHMWPE Nanocomposite Coatings Reinforced with Alumina (Al2O3) Nanoparticles for Tribological Applications

“…Just like in the case of bulk UHMWPE, it is essential to improve the load bearing capacity of the UHMWPE coating for better performance. One of the strategies used by researchers is to develop UHMWPE nanocomposite and hybrid nanocomposite coatings reinforced with various nanofillers, such as carbon nanotubes (CNTs) [27,28], graphene [29], nanoclay [30], and nanoclay/CNTs [31]. Azam et al [30] reinforced UHMWPE with different wt % of nanoclay and found that 1.5 wt % nanoclay-reinforced UHMWPE coating did not fail until 100,000 cycles at a normal load of 9 N and a linear speed of 0.1 m/s.…”

Recent Advances in UHMWPE/UHMWPE Nanocomposite/UHMWPE Hybrid Nanocomposite Polymer Coatings for Tribological Applications: A Comprehensive Review

“…Azam et al [ 75 ] conducted one such study whereby they developed a novel hybrid nanocomposite coating of UHMWPE reinforced with two nanofillers, namely: nanoclay (C15A) and carbon nanotubes (CNTs). They selected nanoclay based upon its excellent mechanical properties and barrier properties.…”

“…Raman spectroscopy : Researchers have also used Raman spectroscopy to ascertain the dispersion of the nanofillers and also to evaluate their interfacial interaction with the UHMWPE matrix. Umar et al [ 75 , 76 ], used Raman spectroscopy to evaluate the interaction of CNTs with the UHMWPE matrix, based upon the shifting of the peaks corresponding to the G-band to higher wave numbers. The shifting of the G band towards higher frequencies is attributed to the disentanglement of the CNTs in the UHMWPE matrix as a result of polymer penetration into the CNT bundles, resulting in a good load transfer.…”

“…Scanning electron microscopy (SEM)/energy dispersive X-Ray analysis (EDX): One of the most common characterization technique used to quantitatively analyze the dispersion of the nanofillers within the UHMWPE matrix is SEM in conjunction with EDX which helps in obtaining the elemental mapping of the nanofillers [ 63 , 68 , 69 , 75 , 76 ]. The combination of these two techniques has also been used to ascertain the failure or the non-failure of the coatings by most of the researchers.…”

“…Ball on disk (point contact) : This configuration is the most predominantly used wear test configuration in most of the studies because of the high contact pressures it simulates due to the point contact [ 52 , 53 , 54 , 55 , 56 , 57 , 58 , 60 , 61 , 62 , 66 , 67 , 68 , 72 , 75 , 76 ]. This helps in testing the coating at very high contact pressures, which in turn helps in determining the PV limits of the coating.…”