Thrust-washer tribological evaluation of PS304 coatings against Rene 41

To prevent surface damage, roughening, and wear of foil bearings during startup and shutdown conditions when speeds become insufficient to provide hydrodynamic air films, plasma-sprayed solid lubricant PS304 has been used as a journal coating. With increasing demands for operational bearing temperature, Rene 41 is one candidate material that may be considered as a replacement for current Inconel X-750 foil materials. In this study, the tribological behavior of plasma-sprayed PS304 coatings, as well as potentially smoother HVOF-sprayed PS304 coatings, was characterized against Rene 41 and Inconel X-750 counterfaces in thrust-washer tests. Tribological behavior of Rene 41 against plasma- and HVOF-sprayed PS304 coatings, and uncoated 13-8 stainless steel, at 538 °C was found to be equivalent to the high-temperature behavior of Inconel X-750 against the same surfaces. Typical wear factors found for the coatings were in 1.5-3 × 10−4 mm3/N m range, while the coefficients of friction were generally about 0.4.