Investigation of the change of mechanical performance and properties of the 321 quality stainless steel in the cryogenic process

In this study, the mechanical properties of AISI 321 quality stainless steel, which is deep cryogenically treated using liquid nitrogen direct cooling method, were investigated. The material samples were tempered at 450 °C at the end of the cryogenic treatment with 24 hours, 36 hours and 48 hours at a temperature of -196 °C. Corrosion, abrasion and tensile-rupture tests were performed on the samples exposed to these processes and the control sample. In addition, 100x, 500x and 1000x images of the cryogenically treated and corrosion-tested sample surfaces were examined by electron microscopy. When the test results of the cryogenically treated samples are compared with the test results of the control sample, the corrosion and abrasion test results have adversely affected the mechanical properties of the material rather than being good as expected. In the tensile-rupture test, some improvement was observed in the strength of the samples. Different results from previous studies were obtained, as cryogenically treated samples were abruptly cooled without a controlled manner. When the electronic microscope images were examined, a visual analysis of the effects of the cryogenic process applied with sudden cooling on the sample surface was made. Accordingly, in the last section, the effects of this cryogenic process on 321 grade stainless steel are evaluated and what should be considered in future studies is given.