Abstract
Hydrogen embrittlement of high strength steels is largely studied in order to understand the relationship between the metallurgical defects and the diffusion and segregation of hydrogen. Different models have been proposed to explain the hydrogen embrittlement that could lead to premature or delayed fracture. In the case of delayed fracture, the role of the different hydrogen species is not well understood, and the impact of the redistribution of hydrogen that may occur during the baking process on the fracture mode is still under consideration. The objective of our study is to give more precise information on the impact of baking process (temperature, time) on the hydrogen distribution that may control the delayed fracture of martensitic steels. It was observed that the increase of baking temperature shifted the kinetic release of hydrogen towards shorter times. It was reported that a part of the diffusible hydrogen is moved towards deeper traps. Evolution of the mechanical resistance during a tensile test after different baking times at 20°C shows a progressive loss of ductility during the first hours associated with a partial brittle facture, then a total recovery is obtained at longer baking time. This loss of ductility could be correlated with the release kinetic of the diffusible hydrogen during the baking process.
