The effect of compositional tailoring on the thermal expansion and tribological properties of PS300: A solid lubricant composite coating

This paper describes a research program in which the goal is to alter the thermal expansion coefficient of a composite solid lubricant coating, PS300, by compositional tailoring. PS300 is a plasma-sprayed coating consisting of chrome oxide, silver and barium fluoride/calcium fluoride eutectic in NiCr binder. By adjusting the composition, the thermal expansion coefficient can be altered, and hence chosen, to more closely match a selected substrate preventing coating spallation at extreme temperatures. Thermal expansion coefficients (CTEs) for a variety of compositions were measured from 25 degrees to 800 degrees C using a commercial dilatometer. The CTEs ranged from 7.0 to 13 x 10(-6)/degrees C depending on the binder content. Subsequent tribological testing of a modified composition indicated that friction and wear properties were generally comparable, and for some operating conditions superior, to the original composition.