Development of lean alloyed austenitic stainless steels with reduced tendency to hydrogen environment embrittlement

Hydrogen gas is believed to play a more important role for energy supply in future instationary and mobile applications. In most cases, metallic materials are embrittled when hydrogen atoms are dissolved interstitially into their lattice. Concerning steels, in particular the ductility of ferritic grades is degraded in the presence of hydrogen. In contrast, austenitic steels usually show a lower tendency to hydrogen embrittlement. However, the so-called "metastable" austenitic steels are prone to hydrogen environmental embrittlement (HEE), too. Here, AISI 304 type austenitic steel was tensile tested in air at ambient pressure and in a 400 bar hydrogen gas atmosphere at room temperature. The screening of different alloys in the compositional range of the AIS1 304 standard was performed with the ambition to optimize alloying for hydrogen applications. The results of the mechanical tests reveal the influence of the alloying elements Cr, Ni, Mn and Si on HEE. Besides nickel, a positive influence of silicon and chromium was found. Experimental results are supported by thermodynamic equilibrium calculations concerning austenite stability and stacking fault energy. All in all, the results of this work are useful for alloy design for hydrogen applications. A concept for a lean alloyed austenitic stainless steel is finally presented.