Scratch test method: Energy dissipation and crack morphology

Abstract

Abrasive wear is one of the most dominant wear mechanisms in industrial applications. Abrasive particles groove the metallic surface under various tribological interactions. Different wear mechanisms show a major influence on the abrasive wear behaviour, e.g. depending on the kinematic properties of abrasive particles. The scratch test method can be used to investigate a two-body-abrasion on a lab-scale and is defined as an ideal single tribological contact. Depending on the material behaviour, a certain amount of elastic and plastic deformation occurs during the scratch test. Especially, the characteristics of plastic deformation can give important information about the wear behaviour of the material investigated.

The objective of this work is the characterization of selected material properties by the use of a standard scratch tester (Millennium 100, TRIBOtechnic) in combination with special analysis methods, e.g. SEM, confocal white light microscope, and Matlab©. The main focus is laid on the characterization of plastic deformation behaviour correlated with energy dissipation during grooving. Furthermore, a detailed study on the interface properties of multi-phase materials is done.

Tests were carried out on single-phase materials with hardness in the range between 270–1100 HV5. The selected single-phase materials can be divided into brass materials, martensitic chromium steels, and complex high-alloyed Fe-based materials. Further investigations were done on multi-phase materials with Ni-based matrix and high content of synthetically added tungsten carbide (WC) with focus on crack initiation and direction of crack propagation. The influence of matrix hardness as well as carbide properties (e.g. shape, content, and orientation) are related to the crack behaviour of the composite material investigated. Results showed a strong correlation between crack morphology and matrix hardness. A soft metallic matrix (450 HV) tends to stop carbide-cracks in the interface, whereas a hard metallic matrix (600 HV) provides less resistance against crack propagation.