Hydrogen Embrittlement Of Automotive Advanced High-Strength Steels

Advanced High Strength Steels (AHSS) have a better combination between strength and ductility than conventional HSS and higher crash resistances are obtained in concomitance with weight reduction of car structural components. These steels have been developed in last decades and their use is rapidly increasing. Notwithstanding, some their important features have to be still understood and studied in order to completely characterize their service behavior. In particular, the high mechanical resistance of AHSS makes hydrogen related problems a great concern for this steel grades. This paper investigates the hydrogen embrittlement (HE) of four AHSS steels. The behavior of one TRIP, two martensitic with different strength levels and one hot stamping steels have been studied using Slow Strain Rate Tensile (SSRT) tests on electrochemically hydrogenated notched samples. The embrittlement susceptibility of these AHSS steels has been correlated mainly to their strength level and to their microstructural features. Finally, the hydrogen critical concentrations for HE, established by SSRT tests, have been compared to Hydrogen contents absorbed during the painting process of Body In White (BIW) structure, experimentally determined during a real cycle in an industrial plant.