Cutting Speed Dependent Microstructure and Transformation Behavior of NiTi Alloy in Dry and Cryogenic Machining

The effects of cutting speed in cryogenic and dry machining on the surface integrity characteristics (the affected layer, microhardness, transformation response, transformation temperature, and latent heat for transformation) of NiTi shape memory alloys are investigated. It has been found that the cutting speed has remarkable effects on the surface and subsurface properties of machined NiTi alloys. Increased cutting speed results in decreased subsurface hardness and increased latent heat for phase transformation. In general, the depth of affected layers decreases with increased cutting speed in dry and cryogenic machining. Chips show a similar behavior as affected layer in terms of transformation response and microhardness. Cryogenic machining is found to have greater effects on the surface and subsurface properties of the machined work material in comparison with dry machining at all given cutting speeds.