Young's Modulus Profile in Kolsterized AISI 316L Steel

Abstract

AISI 316L steel, subjected to a low temperature carburizing treatment (kolstering), has been examined by Mechanical Spectroscopy (MS) and nanoindentation to determine the Youngs modulus of the surface hardened layer (S phase). MS results showed that the average value of elastic modulus of S phase is 202 GPa, a little higher than that of the untreated material.Nanoindentation tests, carried out with loads of 5, 15 and 30 mN, evidence a modulus profile vs depth: E is ~ 400 GPa at a distance from the surface of ~ 110 nm, then decreases to reach the value of the steel substrate (190 GPa) at 33 μm.These results, together with X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES) measurements of carbon concentration profile, can be explained by considering the presence of a very thin surface layer, different from S phase and consisting of a mixed structure of Diamond-like carbon (DLC) and tetrahedral carbon (taC).Furthermore, the same experiments have been carried out also after heat treatments at 450 °C to correlate the modulus change to the decomposition of the metastable S phase leading to the formation of (Cr,Mo)C and Cr23C6 carbides in a Cr-depleted austenitic matrix.

A Novel Methods for Fracture Toughness Evaluation of Tool Steels with Post-Tempering Cryogenic Treatment

“…More details of the nanoindentation test are discussed by Bocchini et al in [31]. During the test, the nanoindenter records the penetration depth h and the load w. The slope dw/dh of the unloading curve at the beginning of unloading can be used to measure E as described by Fougere et al [32], Chen et al [33], and Balijepalli et al [34,35]. Chen et al in [33] showed a typical nanoindentation test load-indentation depth curve, and the author explained how it is possible to calculate the plasticity factor η p , defined as the ratio of plastic deformation work to total deformation work.…”

A Novel Methods for Fracture Toughness Evaluation of Tool Steels with Post-Tempering Cryogenic Treatment

“…More details of the nanoindentation test are discussed by Bocchini et al in [31]. During the test, the nanoindenter records the penetration depth h and the load w. The slope dw/dh of the unloading curve at the beginning of unloading can be used to measure E as described by Fougere et al [32], Chen et al [33], and Balijepalli et al [34,35]. Chen et al in [33] showed a typical nanoindentation test load-indentation depth curve, and the author explained how it is possible to calculate the plasticity factor ηp, defined as the ratio of plastic deformation work to total deformation work.…”

Flat-Top Cylinder Indenter Examination of Duplex Stainless Steel 2205 after Different Heat Treatments

“…are not so critical for the results. However, the FIMEC technique has failed in testing materials with thin coatings or surface layers (e.g., kolsterized stainless steels [29][30][31], nitrided and nitrocarburized steels [32,33]), where the penetration depth is larger than the 100 µm thicknesses of the surface layers. Failure has also been reported in testing welding seams made through such high energy sources as laser and electron beam, where the diameter of the imprint is larger than the MZ widths [34].…”