A better understanding of hydrogen trapping and diffusion in aluminized press-hardenable steels

Abstract

Press hardenable steels (PHS) coated with Al–Si alloy are widely used in the automotive industry owing to their good mechanical properties (Yield Strength >1200 MPa and Tensile Strength >1500 MPa). The presence of Al–Si coating prevents oxidation and decarburization of steel during austenitization. However, aluminized PHS are sensitive to hydrogen absorption during austenitization, while Al–Si coating prevents hydrogen degassing from the specimen at room temperature so that diffusible hydrogen could lead to hydrogen embrittlement in specific conditions.In this study, H trapping in aluminized steels was critically assessed using deuterium sources instead of hydrogen sources during austenitization and thermal desorption analysis (TDA). 22MnB5 steel coated with Al and Al–Si alloys were studied. D is mainly trapped in the dislocations strain field in the steel substrate of aluminized steels and it is responsible for the three main D2 desorption peaks in Al and Al–Si coated steels. Multiple peaks observed on D2 desorption profiles of Al and Al–Si coated steels are explained by the preferential desorption path of D depending on the sample temperature.