Targeting micro-sectioning—A technique to study subsurface features in worn specimens

Traditional preparation of metallographic cross sections by cutting, polishing and etching has a long and successful history of revealing grain sizes, phase composition, gradients, etc. However, the technique is limited with respect to precision in the positioning of the cross section, and it also tends to inadvertently remove brittle constituents and conceal cracks and small details close to ductile phases, that may become smeared out by the polishing. The present paper presents an alternative cross sectioning technique for worn surfaces, developed to automatically reveal weak zones in the surface layer of a material, without the need of precise positioning, and also avoiding inadvertent removal of brittle phases. The technique is applicable to materials that exhibit brittle fracture, and is normally used for characterisation of unworn materials. It is primarily intended for studies in the SEM, since the cross sections produced typically exhibit too coarse topography to be sharply pictured in the light optical microscope. The simple and rapid preparation technique is described and examples from worn cemented carbide rock drills and hot rolls are presented to illustrate some of the capabilities of the technique.