Investigation of the Effect of Cryogenic Treatment on the Microstructure and Hardness of Low-Alloy Steel Alloy

In this research work, the effect of cryogenic treatment on the microstructure and hardness properties of 35XGCL (analog is JIS G 5111) low-alloy steel alloy was investigated. During the study, the samples were initially subjected to conventional heat treatment. After heat treatment, a step-by-step cryogenic treatment method in a liquid nitrogen environment was applied to a portion of the samples. Microstructural analyses were carried out using an optical metallurgical microscope. Hardness tests were performed according to the Rockwell HRC scale. The analyses showed that cryogenic treatment significantly reduced the amount of retained austenite and promoted the formation of a fine dispersed martensitic structure. In addition, uniform precipitation of ε-carbides and secondary carbides of the Fe₃C type was also observed. As a result of these microstructural changes, an increase in the hardness of the alloy was experimentally confirmed. The obtained results confirm that the cryogenic treatment method is a promising approach for machine components operating under high loads and abrasive environments.