Performance of W–TI-(N) coated pins in lubricated pin-on-disk tests

Abstract

W–Ti-(N) thin films were deposited on polished bearing steel balls by dc magnetron sputtering varying the partial pressure ratio, pN 2/pAr . The tribological behaviour was accessed by pin-on-disk testing with contact geometry of uncoated and coated 100Cr6 balls sliding against uncoated different disk materials used as stamping sheet. Different types and amounts of lubricants were used in the tests. In non-lubricated tests, friction coefficients ( μ) as high as 0.8 were achieved. For the more ductile sheet materials (Al alloy and Zn-coated steel) strong adhesion was observed. The best compromise between low wear rate and low friction coefficient was achieved for N-containing coatings deposited without ion gun assistance. In lubricated conditions, a significant decrease of the friction coefficient down to 0.05 and a reduction of the wear coefficient in more than one order of magnitude down to < 10 − 16 m 2N − 1 were reached in relation to non-lubricated tests. Very good tribological results were achieved using the corrosion protection oil as lubricant, with amounts usually applied for protection of sheet materials (2 g/m 2). It was found that the wear coefficient of the coated ball decreased linearly with increasing hardness of the coating, being the best that deposited with N contents in the range from 35 at.% to 40 at.%. The tribological performance of the coated samples was approximately constant even when the amount of used lubricant was reduced to only 25% of the initial value (0.5 g/m 2).