Cryogenic Treatment of Chromium–Molybdenum–Vanadium Steels: Unveiling Microstructural Features and Improved Mechanical Properties

The study investigates the impact of cryogenic treatment (CT) on the microstructural characteristics and mechanical properties of chromium–molybdenum–vanadium (CrMoV) steels. The microstructures of CrMoV steels were extensively characterized using optical microscopy, scanning electron microscopy, and X-ray diffraction after they underwent CT in this study. Changes in grain size, phase composition, and precipitate distribution were examined to evaluate the impact of the CT on the steel's microstructure. Hardness, tensile strength, and elongation tests were also used to assess the treated CrMoV steels' mechanical characteristics. The investigation aimed to ascertain whether the steel's overall performance was enhanced by CT and to what extent it affected these important mechanical properties. Lastly, Charpy V-notch impact tests were used to evaluate the treated CrMoV steels' impact behavior. In order to understand how CT affected the steel's capacity to sustain dynamic loading circumstances, the impact toughness and energy absorption capabilities were examined. Recrystallization and restriction of grain growth during annealing reduced the average grain size, and further, grain refinement took place during CT. The CT samples had tiny precipitates generated inside them, according to SEM examination. These precipitates are essential for strengthening the substance and preventing grain development. By encouraging the production of these precipitates, the CT strengthened and further refined the microstructure. Phase changes, such as the introduction of new phases or modifications to the relative phase fractions, were seen in the CT samples. CT also caused phase shifts, such as converting residual austenite to martensite. The hardness, tensile strength, and impact energy values of the cryogenic-treated specimens showed a considerable improvement compared to the untreated samples. © 2024, The Institution of Engineers (India).