Influence of Advanced Coated Tools on Machinability Characteristics of Incoloy 825

Abstract

With vast application of nickel-based super alloys in strategic fields, it has become increasingly necessary to evaluate the performance of advanced cutting tools for machining such alloys. In order to have elementary knowledge on machinability characteris tics of Incoloy 825 which was so far unknown, in the initial stage of experiment, tool wear and its mechanism, chip characteristics and surface integrity during dry machining were first studied using uncoated and chemical vapour deposition (CVD) multilayer TiN/TiCN/Al2O3/ZrCN coated tool with different cutting speeds. The coated tool could not improve surface finish, but outperformed its uncoated counterpart in terms of other aspects. In the second stage of the study, the primary objective was to recommend suitable cutting tool for machining Incoloy 825. Detailed study was undertaken using commercially available uncoated, CVD and physical vapour deposition (PVD) coated carbide tools, the performance of which was comparatively evaluated in terms of surface roughness, cutting temperature, cutting force, coefficient of friction, tool wear and its mechanism during dry machining. Effect of cutting speed (VC) and feed (f) was also studied. Although, CVD coated tool was not useful in decreasing surface roughness and temperature compared to uncoated one, significant decrease in cutting force and tool wear could be achieved with the same coated tool even under high cutting parameters (Vc=124 m/min and f=0.2 mm/rev). On the other hand, PVD coated tool consisting of alternate layers of TiAlN/TiN outperformed the other tools in terms of all machinability characteristics that have been studied. This might be attributed to excellent anti-friction and anti-sticking property of TiN and good toughness which is a salient feature of PVD technique as well as multilayer configuration, in combination with thermally resistant TiAlN phase. In the final stage of the research work, the feasibility of best performing PVD coated tool was evaluated under environment-friendly dry machining condition in comparison with uncoated tool under conventional flood cooling and minimum quantity lubrication (MQL). Although temperature obtained with PVD coated tool under dry machining has always been significantly more than wet environment, the same coated tool remarkably brought down cutting force, surface roughness and tool wear under dry environment. The results achieved under both rough and finish modes of machining clearly established the use of PVD coated tool under dry environment as a sustainable strategy for achieving green machining of nickel-based super alloys.