Scratch Testing

This article provides a detailed analysis of instrumented scratch testing techniques. These devices are generally used to qualitatively characterize coatings and thin films. Interpretation of the data delivered by these instruments has been facilitated by the advent of high-performance tools such as panoramic imaging, scratch test profile tracking and spatial synchronization during optical observation of a scratch. In addition, the ability to model the deformation of a coating and its substrate as a function of applied load means that test parameters can be adjusted to favor positioning of the maximum stress field not far from the interface. This has led to the development of a wide range of indenters with appropriate contact conditions and pressures.

Significant progress has also been made in using the scratch technique to measure mechanical properties related to adhesion, such as toughness, hardness and viscoelasticity. Similarly, the combined use of scratch testing with other techniques such as acoustic microscopy, Raman spectroscopy, in situ microscopy, etc. has provided additional information on induced damage (cracking, fatigue, fracture) that was not previously systematically accessible or exploitable. The article reviews these developments and outlines the challenges ahead.