Indentation size effect in steels with different carbon contents and microstructures

Indentation Size Effect (ISE) in steels having a wide spectrum of carbon (C) concentrations (wt-%) 0.002 (interstitial-free), 0.07 (microalloyed), 0.19 (low carbon), 0.32 (medium carbon), and 0.7 (high carbon), and microstructures were investigated using Vickers micro-hardness tester. A decrease in micro-hardness with increasing load, i.e. ISE, is observed in all the samples except microalloyed steel. The empirical relations, such as the Nix and Gao model, Minimum Resistance model, and Proportional Specimen Resistance (PSR) model, were used to determine the load-independent or true hardness values. Nix and Gao model was adopted to determine the plastically deformed zone (PDZ) size under the indenter and subsequently correlated with ISE in the materials. It is observed that ISE is absent when the PDZ size becomes comparable to or larger than the grain size of the material.

Automated summary

The study investigated the Indentation Size Effect (ISE) in steels with varying carbon concentrations using a Vickers micro-hardness tester. It was observed that the micro-hardness decreases with increasing load in all samples except for microalloyed steel. Different empirical models were utilized to determine the load-independent hardness values, and the Nix and Gao model was applied to assess the plastically deformed zone (PDZ) size and its correlation with ISE. It was found that the absence of ISE occurs when PDZ size becomes comparable to or larger than the grain size of the material.