Investigate the comparative performance of dry turning Monel 400 alloy by untreated and cryo-treated AlTiN carbide tools

This study describes the cutting performance of Monel 400 alloy using a cryo-treated AlTiN carbide tool. The AlTiN carbide tool was cryo-treated at -196 degrees C for 24 h of soaking at a cooling rate of 0.5 degrees C/min and then tempered at 200 degrees C for 2 h at a heating rate of 0.5 degrees C/min. In this work, we evaluate and compare the hardness, composition, and phases of untreated and cryo-treated AlTiN-coated carbide inserts and also the turning performance of Monel 400 alloy. The machinability characteristics of cutting temperature, turning force, roughness parameter (Ra), form of chip, and SEM-EDS analysis of turned inserts are evaluated and then compared. It was found that the cryo-treated (CT) inserts offered a higher hardness value by 1.5% than the untreated (UT) ones, due to the formation of a new hard surface coating with cryogenic treatment. Cryo-treated AlTiN coated carbide inserts provided the following benefits over untreated ones: lower the cutting temperature at the cutting zone by a maximum of 10%; decreased the cutting force by 6-14%; reduced the R-a values in the turned surface by a maximum of 83%; a reduction in the size of the serrated form of chip; a reduced rate of insert wear; and lower deposition of work material constituents in the turned insert. The reason is enhanced resistance to wear due to an increase in hardness and the formation of a new hard surface coating with cryo-treated AlTiN coated carbide inserts, which was confirmed by analyses of hardness, SEM coupled with EDS, and X-ray diffraction. From the comparison of the characterisation and machinability indices of untreated and cryo-treated AlTiN coated carbide inserts, it was found that the cryo-treated AlTiN-coated carbide inserts provided the favourable turning performance of Monel 400 alloy.