Mechanical properties of thin surface layers affected by material removal processes

It is well known that solid surfaces are subjected to local, intense deformation in material removal processes such as machining and grinding [L.E. Samuels, Metallographic Polishing by Mechanical Methods, American Society for Metals, Metals Park, Ohio, 1982]. Little is known about the mechanical and physical properties of these highly deformed layers. Here, we describe an approach for analyzing the mechanical properties of thin surface layers affected by material removal processes. The approach involves making a taper-section of the desired surface to intrinsically magnify it, followed by nano-indentation of the tape-sectioned region. The approach has been applied to high-strength steels which were subjected to machining or grinding. The results show that the deformed layers are only a few micrometers in thickness; significant changes in hardness occur with these layers; and these layers are composed of sub-microcrystalline structures.