Tribological coatings for aerospace applications and the case of WC-Co plasma spray coatings

Abstract

Friction and wear requirements in aerospace systems are dictated by life limiting problems. One challenge is the broad range of contact stresses and sliding speeds for various movable devices. Another challenge is the extreme operation conditions; in particular an aircraft suffers periodical humidity changes depending on the altitude, broad temperature range, abrasive wear by electrostatically attracted dust. This paper discusses conventional WC-12% Co tribological coating deposited by atmospheric plasma spraying. Friction and wear characteristics were analysed using sliding friction tests (pin-on-disc apparatus). Four different test loads were used in order to examine the influence of contact stress on tribological behaviour. From the experimental data obtained plots of the variation of coefficient of friction and the wear rate with sliding distance were constructed. The tensile behaviour of the coated material as well as the corrosion resistance of coated and uncoated specinens was also examined. Having high hardness and good adhesion with the substrate the sprayed coating exhibits satisfactory wear resistance.