TRIBOLOGICAL BEHAVIOR OF ULTRA-THIN SOFT METALLIC DEPOSITS ON HARD SUBSTRATES

The tribological behavior of ultra-thin soft metallic deposits on sili con substrates was investigated for low load sliding applications. The rmal evaporation and ion-beam sputtering deposition techniques were us ed to produce coatings of various apparent thicknesses (1-1000 nm). Sl iding tests were conducted with gold and silver coatings on silicon su bstrates using a reciprocating pin-on-flat type apparatus to study the tribological behavior of these coated specimens. Various tribological parameters were examined for controlling friction and wear of soft me tallic coatings under relatively low loads. Experimental results indic ate that the film thickness, load and coating deposition technique aff ect the frictional behavior of soft metallic coatings. Microscopic obs ervations showed that plowing is the main cause of friction for soft m etallic coatings under relatively low loads. Based on the experimental observations, the film thickness and load dependency of soft coatings were analyzed using the plowing friction model with a modified hardne ss term. This analysis shows that the him thickness and load dependenc y of soft coatings can be reasonably explained using the plowing model .