“…Table 3 lists some test conditions and major parameters of the ball and disc specimens used in the friction coefficient tests of the PTFE coating and the Ag coating in a cryogenic environment. G95Cr18 [22] was selected as the ball specimen material because it was used to manufacture rolling bearings that are widely used in aviation and navigation fields. In the experiment, the sliding velocities between the ball and disc specimens were selected as 0.0 m/s, 0.32 m/s, 0.64 m/s, 0.8 m/s, 1.6 m/s, 3.2 m/s, 4.8 m/s, and 6.4 m/s.…”