Indentation size effects of ferritic/martensitic steels: A comparative experimental and modelling study

Nanoindentation Properties of 18CrNiMo7-6 Steel after Carburizing and Quenching Determined by Continuous Stiffness Measurement Method

“…Hence, H0 and h * could be considered as parameters for a specific indentation. Ana Ruiz-Moreno et al [11] proposed a generalized Nix−Gao model, as below, The straight-line segments of these contact stiffness versus depth curves near the origin point can be extracted by a Hough transform with error angles of 0.01 • and 0.1 • , as shown in Figure 6a−c. The maximum depth of the straight-line segments under different error angles are shown in Figure 6d.…”

“…Hence, H 0 and h * could be considered as parameters for a specific indentation. Ana Ruiz-Moreno et al [11] proposed a generalized Nix−Gao model, as below,…”

“…The reliability of the Nix-Gao model has been confirmed by large numbers of experiments, but small defects still remain, although some improvement have been presented for studying the material's microstructure [10]. Ruiz-Moreno et al [11] proposed a generalized Nix−Gao model to analyze the break-down of the ISE scaling regime for a small indentation depth. These models can accurately describe the nanomechanical properties of most single crystals or polycrystals.…”

Round Robin into Best Practices for the Determination of Indentation Size Effects

“…Eurofer97 samples were cut from broken Charpy specimens prepared from forged bars hardened at 979 • C for 1 h 51 min and tempered at 739 • C for 3 h 42 min. The materials and their tempering treatment were chosen for their featuring a nanoscopic martensite lath structure with characteristic lath sizes in the range of 100 to 200 nm [13] that is fine enough to have nanoindentation probe an effective medium thereby minimizing the effect of grain structure and crystallographic orientation on hardness measured. The materials were cut into plates of 1 mm thickness and polished with successively finer abrasives and polishing solutions (diamond suspensions of 9 µm, 3 µm and 1 µm particles) finalising by a gentle manual polishing in oxide polishing suspension with silica nanoparticles for 5 min.…”

“…Beyond the measurement of mechanical properties at small scale, nanoindentation can also be used as an experimental tool for studying fundamental materials physics such as the formation of dislocation networks, plastic instabilities, and phase transformations [6]. Continuous refinement of experimental and modelling methodologies to assess mechanical properties at local level is enabling nanoindentation as a technique to obtain microstructural information [7][8][9][10][11], notably through the exploitation of indentation size effects (ISE) [12][13][14][15], which represents a link between small-scale mechanical and microstructural properties. However, the usefulness of the extracted information depends on the reliability of nanoindentation measurements.…”