Tribological behaviour of PVD-coated PA plastic material sliding against metal counterparts

Abstract

Abstract The basic performance and properties of tribological films on plastics have been poorly examined by a few scientists until now, even though such research might be interesting for many applications [1] , [2] , [3] , [4] . In this paper the tribological behaviour of metal sliding against PVD-coated PA (polyamide) plastic material is shown. A low-pressure plasma pre-treatment of the plastic substrates was performed with argon, oxygen and an argon/oxygen mixture by a plasma generator at a frequency of 13.56 MHz. A thin sputtered titanium film guarantees good adhesion of tribological PVD coatings. The examined coatings were MoS2:Ti and a-C deposited by a PVD sputter process and a DLC coating deposited by PACVD. The mechanical properties such as microhardness, elasticity and adhesion of different coating systems as well as the tribological properties sliding against metal (pin-on-disc tests) were investigated. Thereby the coefficient of friction and the stick-slip behaviour were studied. Stick-slip could be avoided totally by using these tribological coatings as it could be already seen in the simple sample test. The results of these investigations and the possibility of an application of these coatings in cone-clutches are discussed. The level of friction torques can be set at defined constant values of μ = 0.25 to 0.28 for the a-C or MoS2:Ti coatings and values of 0.12 by depositing a DLC coating on the plastic outer ring of the clutch.