PREPARATION OF SILVER COATINGS TO OBTAIN LOW-FRICTION IN ALTERNATING SLIDING AT 570-DEGREES-C

For valve mechanisms operating at high temperature, friction and wear measurements were performed under conditions similar to those of real operation, i.e. oscillatory movement with higher loading at the end of the cycle in one direction. Pin-on-disk measurements performed at 570-degrees-C under inert gas showed good behaviour of silver coatings with an optimal film thickness of 2 mum. Under these sliding conditions a favourable friction without running-in was obtained if the silver coating was polished prior to heating. Without polishing, unsuccessful running-in followed by rapid destruction of the coating was observed.