Effect of Tool Coating and Cutting Environment on Machinability Characterstics of Nimonic C-263

Abstract

Machining of Nimonic C-263 has always been a challenging task owing to its hot strength, low thermal conductivity, tendency to work harden and affinity towards tool material. Although coated tool has good potential to overcome some of these challenges, selection of coated tool with appropriate deposition technique is of immense significance. The current study attempts to comparatively evaluate various performance measures during machining of Nimonic C-263 such as surface roughness, chip characteristics, cutting temperature and tool wear with particular emphasis on different modes of tool failure for commercially available multi component coated inserts deposited using chemical vapour deposition (CVD), physical vapour deposition (PVD) techniques. Furthermore, performance of uncoated tool was analyzed with respect to PVD and CVD coated tools. Results were also discussed for different cutting speeds (51, 84,124 m/min) and feed rates (0.1, 0.14, 0.2mm/rev), and constant depth of cut (1mm) along with the progression of machining durations (t). Severe plastic deformation and chipping of cutting edge and nose, abrasive nose and flank wear along with formation of built-up-layer (BUL) were identified as possible mechanism behind tool failure. The best machining performance was noted under a low and medium cutting speed of 51m/min and 84m/min respectively with PVD multilayer coated tool. In addition, influence of coolant that is under food and MQL environment was studied in comparison with dry machining using best performing PVD coated tool. It was interesting to note that the performance of PVD coated tool was comparable and sometimes even superior that of uncoated tool given under flood and MQL environment. Therefore, use of PVD multilayer coated tool under dry machining can be degraded as environment friendly technique for machining nickel based super alloy such as Nimonic C-263.