Investigation of micro-abrasion characteristics of thin metallic coatings by in-situ SEM scratch test

The aim of this study was to elucidate the micro-abrasion characteristics of thin metallic coatings through in-situ visualization of the scratch formation process. Pure silver (Ag), pure copper (Cu), and Ag/Cu composite coatings with thicknesses of a few hundred nanometers were deposited on silicon substrates using a magnetron sputtering system. A custom-built pin-on-reciprocator-type tribotester installed inside of a scanning electron microscope (SEM) was utilized to perform the experiments. A single crystal diamond tip was used as the tool in order to represent a hard single asperity. Micro-abrasion mechanisms of the three different coatings were compared by analyzing the friction and scratch characteristics. The friction force measured during the scratch test was directly correlated with the micro-abrasion mechanism. It was found that different chemical and mechanical properties of the coatings led to the formation of different amounts of debris and burrs. Depending on the type of coating, different micro-abrasion mechanisms could be identified.