Investigation of the material separation behaviour of rocks using scratch tests for the design of tool grinding processes

Abstract

The use of natural rocks as cutting tool material poses an environmentally friendly alternative to conventional cutting tool materials. So far, however, the basics of tool grinding processes for rock tools have not been systematically investigated. This study, therefore, presents an investigation of the material removal mechanisms of four different types of rocks and a mono mineral via scratch tests analogous to a face plunge grinding process used in tool grinding. The aim is to contribute to a knowledge-based design of tool grinding processes for rock tools. This also includes a characterization of their mechanical properties. The occurring material removal mechanisms identified by SEM-images as well as width and depth of the scratches are used to evaluate the influence of single grain chip thickness and cutting speed on material removal mechanisms. The results show that ductile material removal is possible for all rocks in certain areas of single grain chip thicknesses ranging from 0.28 µm to 3.75 µm depending on the rock used and the applied cutting speed. Besides this, the results show optima for ductile material removal at single grain chip thicknesses that are up to 87-times higher than predicted by an analytical model. Additionally, recommendations for the design of the tool grinding process of the investigated rocks based on the obtained results are presented.