Development and application of a combined atomic force microscopy-nanoindentation system with a silicon tip and a diamond indenter

A combined atomic force microscopy (AFM)-nanoindentation system was developed which has a silicon tip for imaging and a diamond indenter for indentation testing. The system makes it possible to conduct indentation tests and to obtain high-resolution topographic images on the same position of a specimen without difficult operations. The quality of AFM images was improved by scanning with a silicon tip instead of a diamond tip. The developed system was applied to materials with fine microstructures. First, the mechanical properties and microstructures of tempered martensitic steel were investigated. The improved image of fine carbide particles can confirm the correlation between the local hardness and the carbide density. Second, indentations created on tungsten, nickel and glass were observed and analysed for calibration of the indenter shape, which is important for any nanoindentation tests. It was found that nickel is suitable for the calibration because of its low and uniform elastic recovery. The area function of the indenter, which is the relationship between the depth and the projected area, was directly estimated using AFM images of indentations on nickel. The area function was approximated with the simple form of A(h) = 28.0(h + 11.8)(2). Accordingly, the AFM-nanoindentation system has proven to be valuable for studies on materials with fine microstructures and for the calibration process in nanoindentation tests.