1mm

Proof that the lubricant functioned by lowering gold wear rate in the example of Fig. 6.63 is shown in Fig. 6.64 for a similar experiment, which compares surface damage from runs (144) with cobalt-gold-plated contacts mated to themselves both with and without lubricant. In dry fretting (Fig. 6.64(a)) the gold surface was worn to the nickel underplate; with lubricant (Fig. 6.64(b)), the surface was burnished, and wear was negligible.