Experimental Investigation of Wear and Structural Change During Hybrid Machining

Abstract

This thesis aims at establishing the impact on the cutting tools from a macro- and microscopical point of view when milling Ti6Al4V using an hybrid process. Additionally, the microstructure of the workpiece after this procedure is submitted to analysis, too. The effect of the thermal cycle, that an hybrid procedure exerts on the cutting tool is on the focus of this work. This thermal cycle is intensiffed by the heat input of an inductor and the cooling effect of liquid CO2. Hybrid machining, is a new technique, developed to improve the machinability of certain diffcult to cut materials like titanium and its alloys. An additional heat input is used to soften them. Induction heat assisted machining is on development itself, so that the research on this topic is on its early stage. Previous examinations did not succeed in delivering unambiguous results. In order to be able to set adequate parameters for a good functioning of this technique, a better understanding of how hybrid machining affects the cutting tools is necessary. To observe the wear on the inserts, three sets of experiments are ran, two of them using different induction settings and the other one using minimum quantity lubrication to provide comparison with a current industrial working method. The used cutting tools and the workpiece are submitted to analysis in means of ank wear land evolution, crack examination and volume loss determination. Differences in the wear mechanisms were found; with higher temperatures at the cutting zone (around 200ºC), thermal cracks were more present than with lower ones. On the other hand, transverse cracking was less present with an increase of temperature.