On the Robustness of Scratch Testing for Thin Films: the Issue of Tip Geometry for Critical Load Measurement

Abstract

AbstractScratch and abrasion resistance of hard protective thin films and polymer coatings is often related to their ability to withstand abrasive conditions without fracturing. Wear particles generate catastrophic and severe wear for hard films, and fractured scratches are often very visible on shiny polymer surfaces. Using a particular abrasive particle shape, the fracture resistance of a surface can be characterized by the load required to create fracture damages. The scratch technique has demonstrated its ability to create these damage mechanisms and characterize the critical load for coatings failure. However, this technique does not yet have the reproducibility and robustness required to be implemented in an industrial environment. The major reason for this lack of robustness is the great influence of the indenter geometry on critical load results and the non-reproducibility of the geometry of conical indenters. This paper addresses this issue and presents a fast and robust method to characterize the indenter geometry based on the indentation technique. Indenters, with radii smaller than 1 micron, were used to characterize thin films of different nature and thickness. The influence of tip geometry on the critical load results is presented for paint coatings. The reproducibility of the critical load measurement using different indenter tips of identical geometry, as shown in this paper, represents a considerable technological breakthrough in abrasion testing and demonstrates the scratch test's ability to control the manufacturing quality of thin films in an industrial environment.