One of my university professors, an Electrical Engineer tasked to teach me and others Electrical Engineering for non-Electrical Engineers was once a worker in the space program. Though not directly involved he remembered lengthy discussions about what to use as a lubricant in the extreme cold of space, and graphite was chosen. After the components came back and were disassembled the joints looked like they'd been grinding in sand. Without a gas present in the interstitial spaces between the particles graphite acts as an abrasive and it was literally back to the drawing board for that team.