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    KAYNAKLANMIŞ PASLANMAZ ÇELİK VE KARBON ÇELİĞİNİN MEKANİK ÖZELLİKLERİNE TANELER ARASI KOROZYONUN ETKİSİ
    (2020-08-21) Acar, Furkan
    In this thesis study scope 300 series stainless steel which are used at the nuclear santrals and oil- natural gas refineries were review. 300 series stainless steels contain Cr between %10,5 and %26 and Ni with a min of %8 and %36. However, when austenitic stainless steels are subjected to heat treatment or welding, the material becomes thermally sensitive very quickly and intensely in unstabilized grades. The reason for this event is that a minimum temperature of 600 ° C is exposed to the material for a certain period of time, and the Cr with free C in the grain borders forms the compound called chromium-carbide. Therefore, since the Cr element, which provides the feature of stainless, will be decreased in the grain boundaries, these boundaries are now sensitive to the corona. After knowing that the material was so damaged, different measures were taken, but apart from these, AISI321 and AISI347 quality steels were formed by adding Ti and Nb as a small amount of stabilizer to the alloy. These stabilizer elements do not allow Cr, but first create a compound with C and reduce the amount of free-running carbon. Thus, it is claimed to prevent or slow down intergranular corrosion. Moreover, although it is stabilized against welding rot, that is, intergranular corrosion, there is still a possibility of a threat posed by these stabilized elements in the structure. In the climates where the carbide temperature formed by the stabilizer elements is low, a ""Knife Line Effect"" occurs similar to the intergranular corrosion phenomenon in a narrow area on both sides of the welding structure. Considering all this, as a result of this study, intergranular corrosion was applied to the samples taken from the test tubes ""321-321"", ""316-316"", ""321-1020"" in certain periods and the data obtained were shared by the table and graphics. As a result of the general result obtained, it was understood that the stabilized test samples had a decrease in their mechanical properties coMPared to the waiting times in the solution and there were serious differences between the surfaces in the broken surface SEM examinations.