B23-P-16Multi-layer Method combined with Nano-indentation, FIB and XTEM for Nano-hardness Measurement

Abstract

Nano-indentation is one of important method for measuring precise hardness in thin films with nano-level, where an average value could be led in depth direction. When the hardness is distributed as the function of depth in nanometer scale, we could not get precise hardness. Recently, our group has proposed a new method, named as “multi-layer method” combined with FIB and XTEM [ 1 ]. In this study, the depth dependence of hardness in an ion-irradiated stainless steel was evaluated by the sectioning of damaged region and subsequent nano-indentation. The range of plastically deformed region by the nano-indentation was supplementary investigated by XTEM. When the indentation depth was the critical indentation depth, hc , which was derived from the Nix-Gao plot [ 2 ], the dislocation structure was observed from the specimen surface to right below the bottom of the ion-irradiated region, as shown in figure. To verify the depth dependence of hardness, the “multi-layer method' was applied in this measurement. In this case, the nano-indentation was measured for four different thicknesses after sectioning by FIB. As the result, we got successively reasonable values of local hardness, H L , as a function of depth and damage level; 278, 333, 372 and 408kg/mm 2 for 0, - 0.6, -1.2 and - 1.8 μm from top surface, respectively.