Abstract
Press hardenable steels (PHS) coated with Al-Si alloy are widely used in the automotive industry owing to their good mechanical properties (YS > 1200 MPa and TS > 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.
The purpose of this study is to evaluate to which extent the coating microstructure influences hydrogen desorption during thermal desorption analysis (TDA) of aluminized PHS. In order to assess the role of the alloying elements and/or constitutive phases on deuterium uptake and desorption, ideal systems made of 22MnB5 steel coated with Al and Al-Si alloys were processed. Austenitization of samples was carried out in controlled atmosphere containing D2O instead of H2O in order to avoid any atmospheric contamination which could compromise further accurate quantification. Owing to specific methodology, we demonstrate that some of the deuterium is trapped within the Al-Si coating, but not in the case of the Al coating.