SCANNING ELECTRON MICROSCOPY IN ANALYSIS OF INFLUENCE OF THE ALLOYING ELEMENTS IN STEEL ON WHITE LAYER FORMATION BY HARD TURNING
White Layer (WL) has been known in literature for a couple of decades. In general, the term has been used to describe non-etching, hardened surface layer of machine parts which is seen under an optical microscope as white “featureless” phase on the surface of the base material. The reason for such “metallographic” occurrence of white layer is in the fact that the same is resistant to chemical etching which is carried out in order to prepare the samples for metallographic examination. Metallographic examinations on the optical microscope are limited by wavelength of the visible light and it allowed magnifications about 1000x. In Scanning Electron Microscopy, using the electron beam instead of the visible light this magnification has been increased significantly. In this paper has been shown how the White Layer is seen under SEM microscope in comparing to optical microscopy. The feasibility of the SEM/EDS (Energy Dispersive Spectroscopy) instrumentation has been shown on example of investigating influence of the alloying elements (C, Mn, V and Cr) on WL formation in process of hard turning. It has been revealed that what has been known as a white “featureless” layer under the optical microscopy in SEM analysis has its specific microstructural form that depend on material and conditions in which the WL is formed.