Influence of CVD multilayer coating on machinability characteristics of aerospace grade stainless steel

Abstract

In the recent years, aeroengine superalloys have gained high amount of research interest owing to their wide engineering application particularly in strategic environment.17-4PH (precipitation hardened) stainless steel (SS) is one such grade of aerospace alloys used to manufacture mostly small parts and mainly stator of aircraft engine in place of Titanium alloy for material cost saving.17-4PH SS falls under the category of difficult-to-cut material because of its low thermal conductivity and high ductility. Although most of the research work was concentrated on machinability of Nickel-based and Titanium based superalloy, no such work on the 17-4PH has been reported so far. Today different coated tools are widely used in machining industries. Therefore it is also essential to select suitable coating material for machining such aeroengine alloys. In order to achieve some of the objectives, the research work has been under taken aiming at investigating the influence of cutting speed (100, 140 & 190 m/min) and feed rate (0.16, 0.20 & 0.24) on various machining characteristics like chip morphology, chip reduction coefficient, tool wear, cutting force, cutting temperature and machined surface roughness. The machining operation was carried under constant depth of cut 0.5 mm and at dry environment.CVD multilayer coated (TiN/TiCN/Al2O3/ZrCN) cemented carbide (ISO P30 grade) insert has been chosen for the current study. The performance of the coated tool has also been compared with that of uncoated carbide insert of similar grade and geometry in order to understand the effectiveness of CVD multilayer coated tool during dry machining of 17-4 PH stainless steel.