Influence of Drill Wear to Local Plastic Deformation in the Wall of Drilling Hole

Abstract

Final properties of plastic deformed parts of workpieces are affected by production technological processes. Therefore it is needful to know detailed structure changes of plastic deformed material caused by machining - grinding, drilling etc. Friction of tool to work surface caused one of three areas of plastic deformation in cutting zone. It has great influence to quality of work surface and local mechanical properties of surface layer of workpiece. Influence of drill wear to local plastic deformation in deformation zone around the surface of drilled holes was investigated. Two types of cutting tools were used: high speed steel drill IZAR HSSCO with diameter 6,0 mm surface hardened by boriding and the same one without boride layer. Standard cutting parameters were used. During the machining process, axial component of cutting force and torque were observed. The work piece was bulk from carbon steel Ck45 (1.0503). Wear of the tool was estimated as a wide of wear on tool flank. The local strain in analysed place of probes on their sections was obtained by stereological measurement of degree of grain boundaries orientation, which is proportional to grain boundaries deformation degree. Estimation of grain boundary orientation degree leads to determination of local plastic deformation in arbitrary place of workpiece. These results lead to detailed analysis of material structure changes caused by drilling from which local mechanical properties result.