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Carbon migration phenomenon in high temperature aging process of 12Cr1MoV/304 welding joint

In order to solve the problem that the carbon migration will appear during the service of dissimilar steel welding joint and thus the failure of decarburization layer will occur under the high temperature environment,the carbon migration problem of 12Cr1 M o V lowalloy heat resistant steel and 304 austenitic stainless steel welding joint under different aging time was investigated with the arc surfacing method. The results showthat after the high temperature aging treatment,the microstructure of welding zone is not affected. The carbon supersaturated upper bainite and granular bainite formed in the overheated coarse-grain zone will degrade and transform into the tempered sorbite. The microstructure in the decarburization layer is mainly ferrite containing a small amount of granular cementite. Especially,a large amount of carbides appear in the carburized layer and the complex irregular microstructure alike the martensite forms. Through performing the calculation with the diffusion equation derived on the basis of Fick's law,it is proved that the theoretical curve of carbon diffusion is close to the actual one,which can be used to study the migration mechanism in the carbon diffusion process.