Seuils de dégradation d’une alumine en frottement à grande vitesse contre differents aciers au chrome

Thresholds failure of alumina in sliding friction at high speed against various chromium steels

¹ Société des Céramiques Techniques, Bazet
² Ecole Nationale d’ingénieurs de Tarbes, Tarbes

Abstract

Friction and wear of alumina sliding against two chromium steels and against itself under both dry and wet conditions are reported. Tests were performed using a pin-on-disc device. Loads and speeds respectively ranged from 5 to 300 N and 3 to 10.7m/s.

The evolution of the friction coefficient and wear rates point out the existence of a load threshold correlated with the sudden degradation of the ceramic under both wet and dry conditions. Below the threshold, steels exhibit a moderate wear rate while ceramic remains undamaged. Worn surfaces show abrasion grooves on steels and thickening metallic layers on the ceramic. On both sides the threshold, the ceramic damage is induced by its grains boundaries failure which leads to a coarse roughness and the emission of abrasive scraps. The circulation of these latter rises the metal wear but metallic layers thickness decreases on the ceramic. Water in the contact strongly lowers the value of the threshold and the friction coefficient value. The mechanical, thermal and chemical effects of load, speed and water are discussed with regard to damage undergone by the sliding bodies. A particular emphasis is focussed on the calculation of average and maximum temperatures occuring in the contact in relation with ceramic grain boudaries damage.