Tribological behaviors of a magnetron sputtered CrSiN coating under ambient air and wet environments

Tribological behaviors of a magnetron sputtered CrSiN coating with 12.5 at.% Si were studied by ball-on-plate sliding tests in three environments, including ambient air, deionized water, and 3.5 wt% NaCl water. Then in-situ microscopic examinations on the wear tracks were followed by the combination of scanning electron microscopy (SEM), Energy Dispersive X-ray spectrometry (EDX), and a focused ion-beam system (FIB). Under air ambient the coating exhibited a friction coefficient of ~ 0.47 and a specific wear rate of 1.2 × 10− 16 m3/N m, corresponding to a mild wear mainly dominated with tribo-oxidation. The tribological behavior of the coating appeared similar features under the deionized water and the 3.5 wt% NaCl water. The friction coefficients were lower (~ 0.24) and the specific wear rates increased almost an order of magnitude, which might be attributed to more tribochemical reactions occurred under the wet conditions. No or little corrosive effect was observed in the coating-substrate system during the 2.16 × 104 sliding cycles under the 3.5 wt% NaCl water. The microscope characterization indicated that the reactive agents could not diffuse to the substrate, since the cracks with limited lengths were not throughout the whole coating.