Surface analysis, microstructural characterization and local corrosion processes in decarburized SAE 9254 spring steel

Abstract

The aim of the present work was to study the surface chemistry, microstructure and local corrosion processes at the decarburized layer of the SAE 9254 automotive spring steel. The samples were austenitized at 850 and 900 °C, and oil quenched. The microstructure was investigated using confocal laser scanning microscopy and scanning electron microscopy. The surface chemistry was analyzed by X-ray photoelectron spectroscopy. Electrochemical impedance spectroscopy and potentiodynamic polarization were employed to assess the global corrosion behavior of the decarburized samples. Scanning electrochemical microscopy (SECM) was used to evaluate the influence of decarburization on the local corrosion activity. Microstructural characterization and XPS analysis indicate a dependence of the local electrochemical processes with the steel microconstituents and Si oxides in the decarburized layer.