WEAR-RESISTING OXIDE-FILMS FOR 900-DEGREES-C

A study was conducted to develop low-friction,wear-resistant surfaces on high temperature alloys for the temperature range from 26 degrees C to 900 degrees C. The approach investigated consists of modifying the naturally occurring oxide film in order to improve its tribological p roperties. improvement is needed at low temperatures where the oxide f ilm, previously formed at high temperature, spalls due to stresses ind uced by sliding. Experiments with Ti, W and Ta additions show a benefi cial effect when added to Ni and Ni-base alloys. Low friction can be m aintained down to 100 degrees C from 900 degrees C. For unalloyed Ni f riction and surface damage increases at 400 degrees C to 500 degrees C . Two new alloys were perpared based on the beneficial results of bina ry alloys and ZrO2 diffusion in Ni. Low friction at temperature above 500 degrees C and reasonable values (0.32 similar to 0.42) at low temp erature are obtained.