OSCILLATING SLIDING WEAR OF TIB2-ZRO2 AND TIC-ZRO2 SURFACE ALLOYED AL2O3 CERAMIC AT DIFFERENT HUMIDITY

A commercial alumina ceramic was surface-alloyed by adding TiB2 and Ti C in addition to ZrO2 using infrared CO2 laser radiation. Aside from t he type of hard particles their volume fraction was varied between 6 a nd 31%. The average thickness of the alloyed surface layer was about 1 50 mu m. Tribological tests were carried out unlubricated under oscill ating sliding contact against alumina counterbodies at relative humidi ties of 3 and 50% as well as in distilled water.Ceramographic studies showed that multiphase structures containing hard particles of TiC or TiB2 embedded in the Al2O3 matrix were obtained by alloying. In additi on Al-Zr-Ti-O complex phases were analyzed by using X-ray diffraction technique. Compared to the commercially available alumina ceramic A123 , laser alloying reduced the friction coefficient and improved substan tially the wear resistance under the applied conditions of tribologica l testing. It was found that tribological behaviour was strongly influ enced by environmental humidity in addition to the effect of the type and volume fraction of the phases produced by alloying. The unalloyed alumina ceramic depended more sensitively on humidity than the alloyed ceramic.