Investigation of Machinability of Stainless Steel with Cryo-Treated PVD Carbide Inserts

Abstract

The use of thermal treatments to enhance mechanical properties of metal components is an ancient art which is used until today. But lately focus of researchers shifted towards the concepts of sub-zero treatments. In the present investigation, PVD coated and uncoated carbide inserts were subjected to deep cryogenic treatment(-1960C) in order to investigate the machinability of stainless steel. Micro-structural study, elemental characterization and crystallographic phase orientations were studied with the help of scanning electron microscopy, energy dispersion X-ray spectroscopy and X-ray diffraction respectively. It was observed that cryo-treatment resulted in the formation of eta-phase in metal matrix. The turning tests were conducted at three different cutting speeds(50, 70 and 90m/min), feed rate(0.04, 0.05 and 0.06mm/min) and depth of cut (0.1, 0.2 and 0.3mm). The influence of cryo-treatments on carbide inserts in terms of flank wear of the cutting tool inserts, surface finish of the machined work-pieces and cutting forces has been investigated. It was observed that there was significant improvement of resistance to flank wear with enhancement of tool life. The surface finish obtained is better with deep cryo-genic treated carbide tools than untreated carbide tools. A comparative study on machinability was carried out between carbide insets cryo-treated at different conditions.