VIBRATION MONITORING IN SLIDING WEAR OF PLASMA-SPRAYED CERAMICS

Dry frictional contact between two surfaces, one made of plasma spraye d ceramic coatings of Al2O3 and Al2O3-TiO2 combination and the other m ade of steel, is analyzed. The experiments were conducted using a pin- on-disc set-up in the load range of 5-35 N and for sliding distances u p to 14 km. The interactions between friction, wear and vibrations due to influence of normal load, sliding speed and system dynamics are in vestigated in the present paper. Two vibration parameters of pin in th e load direction (vertical) are monitored, namely the r.m.s. accelerat ion and the kurtosis, which seem to be influenced considerably by the wear process and indicate correlation with wear mechanisms taking plac e such as stick-slip and grain pull-out, as evidenced by scanning elec tron microscopy of worn surfaces. The study shows that a range of freq uency is to be utilized for vibration monitoring to include natural fr equencies of the system consisting of pin in contact with disc. This c ould be estimated by a standard impulse hammer test. The pin accelerat ion decreases with increase in load and sliding distance, but with res pect to sliding speed, the vibration level initially decreases but inc reases beyond the sliding speed of 1.5 m s(-1). Among the three cerami c coatings, TiO2 is found to be most wear resistant, exhibiting the lo west friction coefficient and a low vibration level. Variation in kurt osis with run-in wear indicates smoothing of Al2O3 due to grain pull o ut. (C) 1997 Elsevier Science S.A.