Experimental Analysis of the Influence of Combined Heat and Cryogenic Treatment on Mechanical Properties of Steel

The main emphasis of the research is to analyse the variation in the behaviour of properties of steel after the combined heat and cryogenic treatment. Preheat treatment was done, where the steels were kept at 600 °C for 60 min and then was quenched using saline bath, followed by the cryogenic treatment at 77 K. For the proper comparison of the variation of properties, the cryogenic treatment of steel was carried out at varying soaking time steps of 2, 4, 6 and 8 h for appropriate analysis of the material. Using optical microscopy, it was observed that as compared to the untreated steels, the impacts of combined heat and cryogenically treated samples were having an excellent microstructure and surface texture. The presence of saturated austenite was initially higher for the untreated material but was found to be lowering with the increase in cryogenic soaking time of material. SEM examination visibly specifies the formation of fine and coarse grains on treated and untreated steels, respectively. Microhardness of cryogenically treated materials was amplified by around 29%, when subjected to combined heat and cryogenic treatment. XRD analysis was done to analyse the variation in the friction coefficient for both the sets of specimens, and it was found that 8 h cryogenically treated specimens were having significantly reduced coefficient of friction as compared to untreated steels.