The influence of high-speed machining under different cutting conditions with different tool materials on microstructure, residual stresses and work hardening of Inconel 718 super alloy has been investigated. The cutting/turning was performed using three different tool materials namely carbide, ceramic, and cBN with constant tool geometry under three different cutting environments such as dry machining, minimum quantity lubrication, and flood cooling cutting condition. Subsurface micro-structural changes, grain refinement, and deformation were observed by using CARL ZIESS optical microscope having 50 X to 1500 X magnification, equipped with Clemex vision professional edition image analysis software. The nature induced residual stresses were measured and analysed using X-ray diffraction technique. Micro-hardness on surface and subsurface was measured by using Vickers micro-hardness tester. An attempt has been made to understand the correlation between work hardening, residual stresses and microstructural alteration. © 2017, The Korean Society of Mechanical Engineers and Springer-Verlag GmbH Germany.