Analysis of Subsurface Microstructure and Residual Stresses in Machined Inconel 718 with PCBN and Al2O3-SiCw Tools

Subsurface microstructural alterations and residual stresses caused by machining significantly affect component lifetime and performance by influencing fatigue, creep, and stress corrosion cracking resistance. Assessing the surface quality of a machined part by characterizing subsurface microstructural alterations and residual stresses is essential for ensuring part performance and lifetime in aero-engines and power generators. This comparative study characterizes and analyzes subsurface microstructural alterations and residual stresses in Inconel 718 subjected to high-speed machining with PCBN and whisker-reinforced ceramic cutting tools. Effects of cutting tool materials and microgeometry on subsurface deformation, microstructural alterations, and residual stresses were investigated. Surface and subsurface regions of machined specimens were investigated using X-ray diffraction, electron channeling contrast imaging, and electron back-scatter diffraction to characterize microstructural alterations and measure deformation intensity and depth.