Dry Turning of AISI 304 Austenitic Stainless Steel Using AlTiCrN Coated Insert Produced by HPPMS Technique

Abstract

The current study focuses on dry machining which is ecologically desirable and cost effective. It is also hailed as the future of machining and called as green machining. Quaternary nitride AlTiCrN coating is used for dry turning of AISI 304 austenitic stainless steel. The coating was deposited using “High Power Pulsed Magnetron Sputtering (HPPMS)” technique on ISO K-20 grade cemented carbide insert. Scanning Electron Microscopy (SEM), microhardness tester and scratch tester were used to examine microstructure, microhardness and adhesion of coating. AlTiCrN coating exhibited fine-grained appearance with dense columnar structure. Microhardness was found to be in the range of 34 to36GPa for the thickness of 4.2μm and the scratch adhesive strength (critical load) was found to be 117N. The effects of machining parameters on the surface finish, cutting force, tool wear, chip thickness, and tool life were investigated during the experimentation. Superior surface finish and minimum cutting force were observed at 320 m/min cutting speed and 0.08mm/rev feed whereas optimum tool wear was found in the range of 200 m/min to 260 m/min cutting speed. This can be attributed to the excellent properties of the AlTiCrN coating and formation of stable Cr2O3 or and dense α(Al,Cr)2O3 mixed oxide scales which protects the tool from severe abrasion at elevated temperatures. The findings of the study should provide economic machining solution in case of dry turning of AISI 304 steel, which is otherwise, usually, machined by costly PCD or CBN tools. The present approach and results will be helpful in understanding the machinability of AISI 304 austenitic stainless steel during dry turning for the manufacturing engineers