Characterization of mechanical properties in surface-treated materials

An experimental methodology was developed for identification of mechanical behavior laws, in which the evolution of the stresses and strains in the su rface of the samples is determined by X-ray diffraction and electric resist ance strain gages, respectively, as a function of the loading in four-point bending tests. The determined stress-strain curve is then characteristic o f the near-surface layers of the samples. The method was validated for diff erent steels by comparing the results of samples with homogeneous propertie s on the cross section with the results of tension tests. The developed met hodology was applied to the study of steel samples submitted to surface tre atments, presenting gradients of chemical composition, microstructure, and mechanical properties from the surface to the bulk material.