Mechanical and tribological properties of sputtered Mo–O–N coatings

The article reports on mechanical and tribological properties of Mo–O–N coatings prepared by reactive magnetron sputtering using a continuous and pulsed inlet of oxygen and nitrogen. Main attention was devoted to a detailed investigation of correlations between the coating structure and its mechanical and tribological properties. The structure of coatings was characterized using X-ray diffraction (XRD), the hardness H, the effective Youngʹs modulus E⁎ and the elastic recovery We were measured by a microhardness tester, and the coefficient of friction μ and the coefficient of wear k were determined using a pin-on-disk tribometer. It was found that (1) μ of the Mo–O–N coating correlates quite well with their hardness H and effective Youngʹs modulus E⁎ and depends on its structure, (2) k of the Mo–O–N coatings is almost independent on the value of E⁎ and its value is very low of about ~ 0.15 × 10− 6 mm3/Nm, (3) the incorporation of oxygen in the Mo–N coating increases its coefficient of friction μ at room temperature (RT), and (4) the coefficient of friction μ of both Mo–N and Mo–O–N coatings at first increases with increasing temperature and above ~ 350 °C decreases to the value of μ of the as-deposited coating (μ ≈ 0.4 and 0.5 for the Mo–N and Mo–O–N coatings, respectively).