Machinability Study of AISI 316 Grade Austenitic Stainless Steel Using P 30 Grade Cemented Carbide Insert

Abstract

Austenitic stainless steel is one of the most important engineering materials with wide variety of applications. Superior resistance to corrosion and compatibility in high
temperature and high vacuum have particularly made it an attractive choice. However, the machinability of austenitic stainless steel is not very promising owing to lower thermal
conductivity, higher degree of ductility and work hardenability Grade 316 is the standard molybdenum-bearing grade. Molybdenum gives 316 better corrosion resistance properties than crevice corrosion in chloride environment. It has excellent forming and welding characteristics.
Over the years, cemented carbide (WC-Co) has overcome many drawbacks of high speed steel (HSS) as cutting tool materials and become one of the most versatile cutting
tool materials during machining both ferrous and non ferrous alloys. There are mainly three grades of cemented carbide cutting tools i.e. K, P and M grades. Steel being very ductile in nature produces long, continuous chips during machining. Moreover, iron in steel has greater
affinity towards carbon of WC of the tool. P grade, is more diffusion resistant grade due to presence of more stable carbides like TiC, TaC and NbC. Therefore, P grade is also known as mixed carbide grade and more suitable for machining steel. Since P 30 grade of cemented carbide would provide excellent balance of hardness, wear resistance and toughness, the same grade has been chosen for machining of
stainless steel. In the first phase of work, tool life test would be carried out using three different cutting velocities i.e. 100, 150 and 200 m/min with constant feed of 0.2 mm/rev and constant depth of cut of 1 mm for different duration of machining. Tool life study would be
based on average flank wear, VB= 0.3 mm criterion. Flank wear would be measured using a stereo zoom optical microscope. Therefore, effect of cutting speed on tool life of uncoated P30 grade carbide insert would be studied during dry machining of 316 grade of austenitic stainless steel. Also effect of cutting speed on various chip characteristics during machining of austenitic stainless steel was studied. The different chip characteristic include types of chips, colour of chips, micro and macro morphology of chips, chip thickness and chip reduction coefficient.