A study of the surface integrity after machining by means of non-destructive testing methods

Paper in proceeding, 2013

During metal machining, depending on the cutting conditions, surface and subsurface microstructure alteration are occasionally observed. These alternations are normally referred as “white” and “dark” layers. Due to their different mechanical properties in comparison to the unaffected material, they will have an impact on the finished part. Controlling the quality of the machined parts regarding the surface microstructure alteration by means of non-destructive testing (NDT) methods would be beneficial from production point of view. In this study, the surface integrity of AISI 52100 steel machined at different cutting conditions resulting in white and dark layers with different characteristics were studied. Surface topography, microstructure and residual stresses were examined by using light scattering, optical microscopy and x-ray diffraction (XRD) techniques. Whilst surface characterization was emphasized, one NDT method – magnetic Barkhausen noise (BN) technique – is not well defined for this purpose. The correlation between all the applied techniques was therefore investigated and a preliminary model was developed for the influence of surface roughness, stress conditions and white and dark layer thicknesses on BN signal.