Physical and chemical effects of CeF3 compact in sliding against Hastelloy C in temperatures to 700 degrees C

The dependence of friction coefficient vs, temperature of Hastelloy C/CeF3 compact was studied in the paper. The wear debris was studied by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Findings indicated that CeF3 had physical and chemical effects in sliding at evaluated temperatures. The physical effects were known as preferential orientation, degree of crystallization and plastic deformation. The preferential orientation of plane (002) had a positive effect on friction reduction. The friction coefficients were low as the degrees of crystallization were high. The chemical effect was known as oxidation. The difference between static and sliding conditions was that the starting temperature of the former was higher than that of the latter. The cause was the temperature difference between the sliding surface and environment caused by frictional action. The oxidation of CeF3 compact had a negative effect on its lubricity below 700 degrees C since CeO2 showed poor lubricity within the range of these temperatures. At 700 degrees C, CeO2 exhibited good friction-reducing, transferring and film-forming properties, which means the oxidation above 700 degrees C may have a beneficial effect on friction reduction. (C) 1997 Elsevier Science S.A.