Si3N4-based ceramic cutting tools have been used successfully for machining hard materials, like: cast irons, nickel based alloys etc. Austenitic stainless steel AISI 321 is one of the most difficult-to-cut materials. In order to investigate the wear behavior of Si3N4 ceramic when cutting the stainless steel the wear tests were carried out on a pin-on-disk tribometer, which can simulate a realistic cutting process. The selected load range was from 58.8 N to 235.2 N, the speed range was from 0.8 m/s to 3.2 m/s. The experiment results showed that the wear of Si3N4 ceramic increases with both load and speed. In dry conditions, the wear of ceramic is mainly caused by adhesion between the rubbing surfaces. In water-lubricated conditions, microfracture of the ceramic may be increased due to stress corrosion of water to the ceramic surface, in addition, the wear is also attributed to adhesion and chemical action of water with the Si3N4 surface. Scanning electron microscopy (SEM), electron probe microanalyzer (EPMA), Auger electron spectroscopy (AES) and energy dispersive X-ray analyzer (EDX) were used for examining of the worn surfaces. The wear mechanisms of Si3N4 ceramic sliding against the stainless steel were discussed in detail. (C) 1999 Published by Elsevier Science Limited and Techna S.r.l. All rights reserved.