Optimization of Metallographic Sample Preparation for AFM/SKPFM Based Phase Distinction of Complex and Dual Phase High Strength Steels

Abstract For the comprehensive investigation of advanced high strength steel grades, like complex and dual phase steels, Atomic Force Microscopy (AFM) and Scanning Kelvin Probe Force Microscopy (SKPFM) have proven to be useful tools, especially for analysis of hydrogen permeability of the individual steel phases. However, for these studies a preparation route, exposing the microstructure of the steel, is necessary. Various sample preparation methods were examined, focusing on electropolishing and sputtering, and the selected route was optimized to guarantee reproducibility and stability of the prepared surface. Electropolishing was shown to be highly efficient to selectively reveal the individual steel phases without introducing strong topographical features disturbing the AFM measurements. A subsequent sputtering step was introduced to improve the stability and preservability of the surface up to several months. Finally, distinction of the steel phases via AFM/SKPFM, was complemented and compared with results from EBSD and XRD.