AISI 304 austenitic stainless steel is generally “difficult-to-cut” material than other types of steel on account of their high strength, high work hardening tendency and poor thermal conductivity. The focus of the paper is on the dry, high speed machining which is ecologically desirable and cost effective. It is also the future of machining and called as green machining. PVD multilayered TiN/TiAlN and TiAlN/TiSiN coated inserts were used for dry, high speed turning of AISI 304 austenitic stainless steels material. TiN/TiAlN coating was deposited using “Cathodic Arc Evaporation” (CAE) technique where as TiAlN/TiSiN coating was deposited using “Closed-Field Unbalanced Magnetron Sputtering” (CFUBMS) technique. Coatings are deposited on K-grade (K-20) cemented carbide insert. Scanning Electron Microscopy (SEM), microhardness tester and scratch tester were used to examine microstructure, microhardness and adhesion of coating. The thickness of the both coating was found to be 3.8 ±2 µm. TiN/TiAlN coating demonstrated micro-hardness value 34 GPa where as TiAlN/TiSiN coating shows 37 GPa. The adhesion strength of the TiAlN/TiSiN coating is 86 N and that of TiN/TiAlN coating is 83 N.The turning tests were conducted in dry machining environment at cutting speeds in the range of 100 to 340 m/min, feed in the range of 0.08 to 0.20 mm/rev keeping depth of cut constant at 1 mm. The influences of cutting speed, feed and tool coating were investigated on the machined surface roughness, flank wear and cutting force. TiAlN/TiSiN coated tool showed better performance and exhibited lower cutting forces than TiN/TiAlN coated tool. Built-up edge was not observed during using coated tool due to better thermal stability of the coating. The research work findings will also provide useful economic machining solution in case of dry, high speed turning of AISI 304 stainless steel, which is otherwise usually, machined by costly PCD or CBN tools. The present approach and results will be helpful for understanding the machinability of AISI 304 stainless steel during dry, high speed turning for the manufacturing engineers.
Optimization of process parameters in Electro Discharge Machining of AISI 304 stainless steel