†Precipitation Behaviour and Corrosion Properties of AISI 436 Ti Stabilized Weld Zone

In this study, Precipitation behaviour and their corrosion properties about three types of weld metals adjusted the Ti content of AISI 436 stainless steel welding wire flux were evaluated by examining the microstructure of the welding metal and by conducting an anodic polarisation test after two hours of heat treatment at 850℃ were produced. Microstructural examinations revealed that the sigma phase in the Ti-free specimen was formed by the segregation of Cr-Mo. However, in the Ti-added specimens, the sigma phase did not precipitate instead, TiN formed within the grain matrix. Ti expanded the ferrite region and delayed the formation of the sigma phase. EDS and mapping analyses revealed that the segregation of Cr-Mo occurred where the sigma phase precipitated. Anodic polarisation revealed that the potentials of passive film formation were nearly identical for all samples, but the pitting potential increased as Ti was added, improving the corrosion resistance. Examination of the starting point of pitting corrosion revealed that pitting in the Ti-free specimen began around the Cr-deficient area that surrounded the sigma phase, whereas in the Ti-added specimens, pitting began in the vicinity of the Ti precipitates that were formed within the grain matrix.