Abstract
WC-Co coatings have been used as wear resistant coatings in aero engines for decades, and research is still ongoing to further improve the performance of these coatings through compositional modifications to reduce wear. The coatings are used for unlubricated sliding wear protection in aero compressor parts such as; compressor, disc mid-span stiffeners and compressor aerofoils. In this study, two different graphene nanoplatelets (GNPs) were introduced into the WC-Co (88–12 wt %) coating through a hybrid thermal spray technique. Under the correct injection conditions, hybrid HVOF thermal spray leads to in-situ powder mixing which eliminates the need for premixed powder. The addition of GNPs into the WC-Co coating led to an increase in the porosity of coatings. Both GNPs improved the wear performance of the system against alumina and reduced damage to the counter surface. Against the WC-Co counter body, although in a few cases the GNP incorporated coatings had a higher wear rate, lower deformation on counter bodies were obtained. When wear of counter surfaces and coatings were combined, GNPs improved the wear performance of the system as a whole.
Highlights
In engineering applications, the friction force between moving parts causes wear and subsequent material loss from the surfaces, which leads to degradation and loss of function
Both composite coatings have a porous microstructure and Vickers microhardness of WC-Co + GNP2 was reduced by 25%
Against alumina at 300 rpm, there was a significant increase in wear rates
Summary
The friction force between moving parts causes wear and subsequent material loss from the surfaces, which leads to degradation and loss of function. Studies performed showed that reducing the powder size, increases the temperatures of the particles and creates a more uniform heat distribution. This increases the deformation upon impact which leads to denser, less porous and harder coatings. On the other hand, reduced hardness and fracture toughness increase the wear rate of these coatings as well under dry sliding and three body abrasive wear [10,12,13,14,15,16] Both mechanical properties and wear performance of WC-Co coatings on their own and combined with other metals have been studied extensively in the literature. Graphene has promising results on friction and wear when it is used as a solid-state lubricant or reinforcement material for composite materials
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