Analysis of spherical chips after grinding

Abstract

Grinding is a conventional technological operation necessary for the manufacturing of mechanical parts of precise shapes and sizes with high demands on surface roughness. The machining is done with a tool with an undefined cutting-edge geometry composed of individual hard grains which are connected by a binder. Small cross-section chips form during machining with the grains. These chips undergo great plastic deformations and suffer a heating of such magnitude due to the inner and outer friction that it causes melting and a subsequent forming of a metal ball. The goal of this study is to analyse these balls - chips after grinding, formed during the machining of D2 tool steel with an Al2O3 grinding wheel. 4 types of balls were found and examined. A focused ion beam was employed to sputter a part which allowed the study of their inner area. An analysis of the chemical content was carried out both on the outside and the inside of the ball. The carried-out analysis led to the discovery of two new types of balls that form after grinding.