Tribology-Related Behaviour of Coated Titanium Ball Screw Mechanisms under Thermal-Vacuum Conditions

摘要

Grade 5 Titanium telescopic ball screws have been tested under thermal-vacuum conditions in order to verify performances during on-orbit functioning. A solid multilayer film of Tungsten Carbide/Carbon (WC/C) was deposited on screw surfaces as a lubricant and was then compared with the case of no lubrication, which presently appears promising for many mechanisms. In order to compare experimental results, traditional stainless steel (AISI 4140) mechanisms were also tested and analyzed. The experimental results together with the analytical ones enable to calibrate a numerical contact non-linear model which has been useful for the comprehension of lubricant crack behavior and propagation. The requisites imposed by the space environment, as well as by numerical contact mechanical stresses, have given useful information on a preliminary geometrical configuration and choice of materials, both of which are presented in this paper.