THERMAL DESORPTION ANALYSIS AS A QUANTITATIVE TOOL FOR HYDROGEN TRAPPING IN CRYSTALLINE METALS

Thermal desorption analysis (TDA) is a powerful experimental technique used to characterize the hydrogen trapping in metals. The passage of hydrogen through a metal is hindered by lattice imperfections, which tend to attract and bind it.

The susceptibility of materials to hydrogen embrittlement is directly related to the interaction between traps (defects) and hydrogen. Since trapping affects the metal diffusivity, it has a major influence on the hydrogen assisted cracking (HAC) phenomenon. Hydrogen trapping is usually evaluated on the basis of reaction controlled mechanisms. Our studies are based on the measurements of temperatures of the gas desorption, the heating rate and the acti­vating energy. This work reviews our studies on the interaction between the hydrogen and defects in duplex stainless steels (DSS) using thermal desorption analysis in order to better understand the hydrogen trapping mechanism. We will discuss the hydrogen`s physical trapping and how it affects the hydrogen interaction with DSS.

Our results show that the trapping phenomenon in lean duplex steels (LDS) and super duplex stainless steel (SDSS) can be classified as reversible trapping (≤60 kJ/mol), as well as how it help us to predict the failure of variety of duplex stainless steels in the presence of hydrogen. One of the main conclusions derived from our studies is that the degree of stability of γ phase (S_γ) affects the trap activation energy for hydrogen. LDS will show higher trapping capabilities than those of SDSS; meaning that LDS has a major advantage as a substitute steel for industrial applications. The trapping mechanism and the prediction of failure of the variety of steels will be discussed in details.