Tribological behavior of PS400-related tribopairs for space exploration

PS400 is a multi-component alloy developed by NASA and intended for high temperature bearing applications. This study reports on four mating surfaces, namely bulk 4130 steel, diamond-like carbon (DLC), polycrystalline diamond, and molybdenum boride cobalt chrome coatings sliding against PS400 coating, and the best performing tribopair at 25 and 500 degrees C was identified. The temperature range and sliding speeds simulate extreme conditions for low-speed space-related applications, such as bearings on landing probes for future missions to Venus. PS400 vs. DLC showed low friction and excellent wear resistance up to 500 degrees C. DLC provided good lubrication at 25 degrees C, whereas at 500 degrees C oxide glazes transferred on DLC, maintaining low friction. The worn surfaces and the transfer films were analyzed using different analytical techniques.