A study of indentation for mechanical characterization of the Fe₂B layer

In this study, the indentation properties of the Fe₂B layer were evaluated. The powder-pack boriding process on low-carbon steels was carried out at a temperature of 1273K for 4, 6 and 8h of exposure. First, Vickers indentation testing was performed on the boride layer at a distance of 50μm from the surface of the borided steel with applied loads in the range of 0.0981 to 9.81N for the set of experimental conditions of the boriding process. Furthermore, the hardness-depth profile, the behavior of the Young's modulus, and the elastic and plastic work of indentation were estimated by the instrumented (Berkovich) indentation testing using a constant load of 250 mN along the depth of the Fe₂B layer. The results of the Vickers hardness testing on 50 μm from the surface indicated the presence of the indentation size effect (ISE) in the boride layer, in which the apparent or real hardness was estimated according to the proportional specimen resistance (PSR) model, and the dislocation band (DB) model. Finally, using the results of the instrumented indentation tests along the depth of the boride layer, the thermal residual stresses and the hardness dissipation parameter (HDP) were evaluated as a function of the boriding temperature and exposure time.