1989 年 7 巻 4 号 p. 512-518
The stress corrosion cracking (SCC) resistance of non equlibrium duplex stainless steel weldment was investigated. Non equlibrium duplex stainless steel developed by mixing the powders of both Type 316L and 444 has excellent SCC resistance because the ferritic phase of 444 is nickel free.
The welded joints of this steel revealed higher resistance to SCC in MgCl2 solution than conventional duplex stainless steels. However, the SCC occurred in HAZ in the severe environment of 42% MgCl2 boiling solution. The effect of weld thermal cycle on the SCC resistance of the non equlibrium duplex stainless steel was tested using the simulated HAZ. The HAZ showed the SCC susceptibility in the narrow region heated up to the high temperature because the nickel diffused into ferritic phase from austenitic one. The nickel diffusion between the two phases was investigated. The effect of heating conditions on the SCC susceptibility can be explained by the nickel diffusion theory considering the phase transeformation at the phase interface.