Development of High Concentration References for Measuring Hydrogen Ingress into Steels

Abstract

Hydrogen ingressed into steels has been treated as one of detrimental factors causing the hydrogeninduced damages or failures and its concentrations is generally measured by a hot extraction system calibrated with references. High concentration references above 50.00 wppm is proposed to solve the bottlenecks of conventional references such as thermal instability and lower hydrogen concentrations at room temperature; by varying a mixing amount of titanium hydride as a hydrogen source with its balancing iron bead, the synthesized reference has freely controlable hydrogen concentration and also showed a good thermal stability at room temperature. Hydrogen residue in the iron bead was controlled less than 0.13 wppm by an optimized procedure including wet cleaning and thermal soaking at 300°C for 3 minute. Hydrogen weight fraction in the titanium hydride was calculated by 0.04 based on the assumption of the stoichiometric composition (or TiH2). Hot extraction measurements and theoretical calculations of the hydrogen concentrations were done for the hydride-containing iron beads. Both data showed a good linear correlation each other and a validity of the proposed concept is confirmed emprically.