Improving the resistance to stress corrosion cracking and to hydrogen embrittlement of bainite high strength steel

Susceptibility to pitting corrosion, hydrogen transport, hydrogen embrittlement and susceptibility to stress corrosion cracking have been studied under the "sea water" and the "acid rain" simulated conditions in order to evaluate the optimum chemical composition, heat treatment, microstructure and surface treatment of the high strength low carbon bainite 0.3C-1Cr-1Mn-1Si-1Ni type steel for replacement the airplane parts. Resistance to stress corrosion cracking under the open circuit conditions, associated with the resistance to pitting corrosion in Cl- containing solution increased with decreasing carbon content and after application of shot peening. Resistance to hydrogen embrittlement was also higher for steel with the low carbon content. Shot peening increased the hydrogen trapping efficiency within deformed layer, but the presence of the shot peened layer decreased the hydrogen flux entering the core and thus decreased susceptibility of core to hydrogen embrittlement. The optimal chemical composition, heat treatment and surface treatment parameters, mechanical properties and microstructure of steel providing the improvement of the resistance to SCC in Cl¯ containing environments allowing the replacement of the standard 30HGSNAŻ steel at production of airplane parts have been evaluated.