Abstract
This work deals with the initiation of hydrogen-induced disbonding which occurs at overlay welds of austenitic stainless steel from view of metallurgy. An experiment was done about specimens exposed to elevated temperature under high pressure hydrogen atmosphere.
Hydrogen-induced disbonding was initiated on the inside of carbide layer, which was formed at the interface of overlay and base metal by post weld heat treatment, with the duplex structure of austenite and martensite and/or the austenite structure with 0-10% ferrite respectively. The range of chemical compositions showing these structures corresponded to 20-28% Ni equivalent (Ni*eq).
At these structures by post weld heat treatment, the formation of carbide layer exhibited itself at the austenite grain boundary of the transition zone and accompanied the formation of depletion zone of chromium, α' martensite and stacking fault at that region.
Hydrogen-induced disbonding seems to be caused by the connection between the above metallurgical factors and hydrogen accumulation to the interface of overlay and base metal.
