Masao Nakahara

Nondestructive Evaluation of Hydrogen Absorption Embrittlement of Tantalum and Life Management in Chemical Plant.

Tantalum (Ta) has excellent corrosion resistance, but is rather expensive. Therefore, Ta has been used for critical components in chemical plants operating in highly corrosive environments. However, one typical degradation phenomenon of Ta is hydrogen absorption embrittlement. The object of this paper is to present the case study of a failure analysis on a Ta sheath tube of a thermometer used in a sulfuric-acid-containing environment. In the analysis, the nondestructive evaluation (NDE) method for estimation of hydrogen concentration and the changes in mechanical properties of Ta with hydrogen absorption was examined. Furthermore, with the aim of life extension of the components of interest, a hydrogen desorption procedure to recover the mechanical properties of the samples was also examined. Based on NDE of hydrogen concentration of Ta and hydrogen desorption heat treatment on service-exposed materials, life estimation and management procedures of components in chemical plants are proposed.