Effect of Cryogenic Treatment of Cemented Carbide Inserts on Properties & Performance Evaluation in Machining of Stainless Steel

Abstract

In this research work, the influence of cryogenic treatment on different characteristics of ISO P30 grade cemented carbide insert was studied, followed by performance evaluation in dry turning of AISI 316 grade austenitic stainless steels using untreated and cryo treated carbide inserts. Microstructural characterisation and crystallographic orientation were studied with the help of scanning electron microscopy (SEM) and X-ray diffraction (XRD) respectively. Chemical composition of the untreated and cryo treated inserts were determined using energy dispersive spectroscopy (EDS) through X-ray. Microhardness of the same specimens were evaluated using Vickers microhardness. The results indicated that cryo treatment resulted in formation of hard and wear resistant η phase carbides. At the same time, the concentration of binder phase i.e. cobalt on the top surface region increased. The turning tests were conducted at three different cutting speeds (100, 150, and 200 m/min.) while feed rate and depth of cut were kept constant at 0.2 mm/rev and 1 mm, respectively. The influences of cryogenic treatment were investigated on the average flank wear and chip characteristics. Both the worn parts of the cutting tools as well as the chips were also examined using optical microscopy and SEM. The results showed that cryogenic treatment significantly improved the average flank wear. The cryo treated demonstrated superior resistance to tool wear compared to its untreated counterpart in the entire range of cutting speeds. The chip thickness along with chip reduction coeffiecient was found to decrease for cryo treated insert compared to those for untreated insert during dry turning of AISI 316 grade austenitic stainless steel.