PVD CRXN COATINGS FOR TRIBOLOGICAL APPLICATION ON PISTON RINGS

Besides the established PVD coatings for the wear protection of machin ing tools, this paper deals with coating development and model wear te st results from PVD coatings on piston rings for combustion engines. P iston rings are examples for the application of thin films on commonly used mechanical components. The PVD CrxN coatings are deposited by RF magnetron sputtering and characterized by their fundamental mechanica l properties like thickness, hardness, residual stress and adhesion, w hich are important for the tribological behaviour of the coating subst rate compound. The contact mechanics of the tribological system piston -ring-cylinder are determined by high mechanical loading and changing geometry caused by the sliding kinematics. Therefore, the range of thi ckness is about 7 mu m. The selected rings are made of steel DIN 1.411 2 (DIN X 90 Cr Mo V 18) with a bore diameter of 97.5 mm. The results o f the coating substrate characterization - high hardness, moderate com pressive residual stresses and sufficient adhesion on metallic substra tes - provide good behaviour of coatings in this tribological applicat ion. This is confirmed by the results of the tribological test procedu res which have been performed with ring-on-disc model-wear tests and a short-stroke lest rig. (C) 1997 Elsevier Science S.A.