Evaluation of Hydrogen Content Trapped by Vanadium Precipitates in a Steel

Hydrogen content trapped by vanadium precipitates was evaluated using vanadium bearing martensitic steels which show single TDA desorption peak. The peak consists of desorption from various sorts of trap site with different detrapping activation energy, even if it appears to be a single peak. Experimentally obtained single desorption profile taken from vanadium bearing martensitic steels was decomposed to multiple profiles with different peak temperature. Form of each desorption profile was approximated to Gaussian function. Area surrounded by each Gaussian function was calculated by integrating the functions to obtain decomposed hydrogen contents related to each peak temperature. It was revealed that decomposed profile with 140°C peak was caused by vanadium precipitates trapping, by comparing an amount of vanadium precipitates with decomposed hydrogen contents. Most of hydrogen in vanadium bearing tempered martensitic steel was revealed to be trapped by vanadium precipitates.