Tribological behaviour at room temperature and at 550 degrees C of TiC-based plasma sprayed coatings in fretting gross slip conditions

This paper deals with the investigation of the tribological behaviour of ce rmet plasma sprayed coatings in fretting conditions. Low pressure plasma sp rayed NiCrFeAlTi-TiC, NiCr-(Ti, Ta)C and NiCrMo-(Ti, Ta)C coatings were tes ted at room temperature and at 550 degrees C, against sapphire ball under g ross slip conditions. Air plasma sprayed NiCr and NiCr-TiC coatings, as wel l as the high velocity oxy-fuel WC-Co coating, were investigated for compar ison with the coatings tested in the present study. The coatings were class ified with respect to wear and friction behaviour. The matrix and the carbi de modifications of the NiCr-TiC coating influenced positively the coating wear and friction behaviour The wear resistance of all the coatings decreas ed at high temperature. The NiCrFeAlTi-TiC coating showed the best wear res istance among the TiC-based coatings. At room temperature and at 550 degree s C, the WC-Co coating was more wear resistant than the TiC-based coatings, eventhough the coating cracked in the high temperature tests. The coeffici ents of friction (COFs) of the WC-Co coating, tested against sapphire, were lower than the COFs of the TiC-based coatings at room temperature, but not at 550 degrees C. XRD and SEM investigation of the wear tracks gave inform ation on the active wear mechanisms. (C) 2000 Elsevier Science S.A. All rig hts reserved.