Polyetheretherketone, hexagonal boron nitride, and tungsten carbide cobalt chromium composite coatings: Mechanical and tribological properties

Abstract

Composite powder coatings consisting of polyetheretherketone (PEEK), hexagonal boron nitride (hBN), and tungsten carbide cobalt chromium (WC-CoCr) particles were prepared by mechanical grinding and applied on steel substrates by thermal fusion of the thermoplastic polymer. The coatings contained about 20-60 vol% of hBN and WC-CoCr, and were designed to maximize modulus and hardness and minimize friction coefficient and wear rate. The mechanical and tribological properties of single-and double-layered coatings were characterized using nanoindentation and sliding friction and wear measurements. When the hBN concentration was about 30 vol%, the PEEK-hBN composite modulus was lower than that of neat PEEK, which is attributed to the disruption of PEEK crystallization by the filler particles. Upon the inclusion of WC-CoCr particles, the composite's modulus, and hardness showed a substantial increase beyond PEEK values. Elastic moduli of the mixed-filler systems were closer to the Reuss bound than the Voigt bound and could be correlated well with the coating composition using volume-fraction-weighted powers of component properties. Fitted values of the exponent (called the microstructural coefficient) were consistent with the expected continuity and connectivity of the composite's hard and soft phases. Viscoplastic energy dissipation increased with an increase in the polymer-filler interfacial area but decreased with the soft-phase volume fraction. The plasticity index was found to increase logarithmically with the coating modulus. The specific wear rate increased sharply beyond a composition-dependent critical value of the plasticity index. Mechanical polishing of the coating surfaces using abrasive slurries lowered the friction coefficient but increased the wear rate.

i PP/HDPE blends compatibilized by a polyester: An unconventional concept to valuable products

“…The miscibility of polymer blends is typically described by miscibility parameters such as the binding energy ( E binding ), mixing energy (Δ E mix ), and the Flory-Huggins interaction parameter (χ). These parameters depend on the Hildebrand solubility parameter (δ) and cohesive energy densities (CEDs) ( 33 – 35 ), which can be obtained from molecular dynamics simulations ( 36 – 40 ). For the simulations of the i PP/HDPE blends (with and without PPDL as compatibilizer), four models with different i PP and HDPE ratios were used ( Fig.…”

“…S5 and S6, and table S2). i PP/HDPE blends are immiscible at room temperature, leading to a positive Flory-Huggins interaction parameter (χ) ( 40 , 42 – 44 ) at room temperature. However, these simulations were performed at 190°C (processing temperature), and at this temperature, the molten mixture of iPP/HDPE shows a negative Flory-Huggins interaction parameter (χ), as depicted in Fig.…”

The physical and optical investigations of the tannic acid functionalised Cu-based oxide nanostructures

“…The work speculated that the stacking of the flakes is due to the natural chemical adhesions caused by the quinone 71 , which is responsible for the hydrophobic terminated layer surfaces in all the samples. Hydrophobic surface promotes cohesion between the nanostructures 72 – 74 . This can be visibly proven by the less dispersion and easy sedimentation at the bottom part of the glass vial.…”

Recent Advancements in Materials and Coatings for Biomedical Implants

“…These coatings enhance bioactivity and electrochemical corrosion resistance, especially for implant structural components. Typical examples for the composite coatings are TiO2/PEEK [138], sol-gel glass/PEEK [139], bioactive glass/PEEK [140], h-BN/PEEK [141], Ag/bioactive glass/PEEK [142], and h-BN/bioactive glass/PEEK coatings Figure 1. The role of bioactive coated metallic implants as a potential implant material [127].…”

“…These coatings enhance bioactivity and electrochemical corrosion resistance, especially for implant structural components. Typical examples for the composite coatings are TiO 2 /PEEK [138], sol-gel glass/PEEK [139], bioactive glass/PEEK [140], h-BN/PEEK [141], Ag/bioactive glass/PEEK [142], and h-BN/bioactive glass/PEEK coatings [137]. A combination of bioactive glass embedded in a polymeric matrix of PEEK makes it an interesting material for orthopedic applications as it meets biological and biomechanical requirements for the application.…”