Coefficient of friction and wear of sputtered a-C thin coatings containing Mo

摘要

The paper reports on preparation of ~3000nm thick a-C coatings containing Mo, interrelationships between their mechanical properties, a coefficient of friction μ and wear rate k and the effect of Mo content in the a-C coating on these interrelationships. The Mo-C coatings were prepared by sputtering using an unbalanced magnetron (UM) equipped with a graphite targets (?=100mm, 99.9% purity) fixed to the UM cathode with Mo ring of different inner diameter ?_i. The content of Mo in the a-C coating was controlled by ?_i. It is shown that μ and k of the coating strongly depend not only on its hardness H but also on its effective Young's modulus E~*=E/(1-ν~2), the ratios H/E~*, H~3/E~(*2) and the elastic recovery W_e; here E is the Young's modulus and ν is the Poisson ratio. The ratio H~3/E~(*2) characterizes the resistance of coating to plastic deformation. Coatings with a low amount of Mo composed of nanograins of carbides dispersed in a-C matrix exhibit low values of μ≈0.07 and k≈10~(-7)mm~3/Nm measured with WC ball at the rotation speed v=0.05m/s, total sliding length l=1000m and the load L=2N.