Assessing the impact of the structure and chemical composition of plasma-sprayed coatings on their adhesion and tribological properties

The influence of the structure and chemical composition of thermal coatings on their mechanical properties must be taken into account when choosing optimal plasma spraying modes providing coatings with desired properties. The application of Al2O3 as electrical insulating coatings in thermonuclear reactors is limited by high values of the friction coefficient μ = 0.45–0.95 for sliding without lubrication. Dry sliding friction involves large shear stresses causing cohesive or adhesion failure (delamination, separation, etc.). One way to reduce shear stresses is adding a tribological layer to the most loaded areas of electrical insulating coatings to provide both high tribological and electrical insulating properties. The application of the plasma oxide coating Al2O3-40%TiO2, Cr2O3 as an anti-friction coating is analyzed. It is found that the tribological properties of plasma-sprayed coatings strongly depend on their microstructure, inclusions and cohesive strength. Adhesive strength can also be a factor of the tribological properties of plasma-sprayed coatings.

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