Machinability Study of Duplex Stainless Steel 2205 During Dry Turning

Duplex stainless steels (DSS) are preferred replacement to austenitic stainless steel because of their higher strength leading to economic benefits. However, poor ductility and thermal conductivity along with high toughness make them difficult to machine. In the present investigation, tool wear, cutting force and surface roughness were evaluated during dry turning of DSS 2205 using tungsten carbide inserts coated with AlTiCrN and AlTiN. High Power Impulse Magnetron Sputtering technique was used for coating the substrates. Cutting speeds of 100, 140 and 180 m/min; feed of 0.12, 0.15, and 0.18 mm/rev, and a fixed depth of cut of 0.8 mm were chosen as cutting parameters for dry turning. AlTiCrN coating exhibited highest adhesion strength of 110 N compared to 89 N by AlTiN coating. AlTiCrN coated tools exhibited highest tool life of 7840 mm, with least surface roughness of 0.72 µm and cutting force of 255 N. This is attributed to its excellent physical properties such as good adhesion, higher oxidation resistance and thermal stability, compared to AlTiN coated tool. AlTiCrN and AlTiN coated tools exhibited respectively 6-times and 4-times more tool life than uncoated tools. Combination of high speed (180 m/min) and low feed (0.12 mm/rev) resulted in least surface finish. Regression model developed from the experimental data showed closer agreement (95%) between predicted and experimental values of surface roughness.