Plasma nitrided austenitic stainless steels for automotive hydrogen applications

✍ Scribed by Peter Kaestner; Thorsten Michler; Hans Weidner; Kyong-Tschong Rie; Günter Bräuer

• Publisher: Elsevier Science
• Year: 2008
• Tongue: English
• Weight: 480 KB
• Volume: 203
• Category: Article
• ISSN: 0257-8972
• DOI: 10.1016/j.surfcoat.2008.08.024

✦ Synopsis

This work is focused on the development of plasma diffusion treatments for stainless steels to obtain a higher conductivity of bipolar plates in fuel cells and secondly, to avoid hydrogen embrittlement of stainless steels in case of high pressure hydrogen storage systems by the formation of a single γ C layer. Electrical conductivity and corrosion resistance were enhanced by plasma nitriding. Tests with single cells have shown a 15% higher voltage compared to graphite plates at low temperatures and reduced treatment durations. The substitution of high alloyed stable stainless steel grades by cheaper metastable stainless grades depends on a successful suppression of hydrogen environmental embrittlement. A promising way could be a surface treatment resulting in the formation of a γ C layer on top of the surface. Plasma nitrocarburizing can form such γ C layer, but a variation of treatment temperature and CH 4 content was not successful in suppressing the undesired S-phase as a top layer.