Investigation of factors influencing microscopic interactions between the diamond indenter and material surfaces in nano-indentation

Nano-indentation method was brought forward to replace atomic force microscopy (AFM) in simulating microscopic interactions between abrasive particles and material surfaces during polishing process. And main influencing factors including measuring parameters and material's properties were investigated thoroughly. It was found that contact force between the diamond indenter and a fused silica was about 200 mu N, while it was about 470 mu N between the indenter and an austenitic steel, and in both cases it did not vary with the maximal indentation force (F-max) and the corresponding loading rate. While adhesion force between the indenter and surfaces of the two materials did not change with F-max when the latter was less than its critical value, while it decreased monotonously with increased F-max when the latter was higher than its critical value, with slope -1.8615 for the fused silica and -1.5403 for the austenitic steel, and the critical F-max was about 20 mN for the fused silica and about 50 mN for the austenitic steel. According to analysis on elastic and plastic deformation during loading process and elastic recovery during unloading process, it was deduced that there would produce marked elastic recovery force when the unloading rate determined by F-max was higher, which counteracted the measured adhesion force to some extent and made it less than its corresponding intrinsic value. And material's elasticity had an additional impact. Then it is better to adopt maximal indentation forces less than critical values of materials, to obtain accurate adhesion forces between the indenter and material surfaces, and to simulate accurately microscopic interactions during polishing process. (C) 2015 Elsevier B.V. All rights reserved.