Author : D.Candane, N.Alagumurthi and K.Palaniradja

The study examines the effects of deep cryogenic treatment, applied at -196˚C with 24 hours soaking, on a super alloy high speed steel, AISI T42. Presence of retained austenite at the end of conventional heat treatment and at the end of cryogenic treatment was studied using X-ray diffractometry. XRD analysis confirms elimination of retained austenite from 19 % at the end of conventional heat treatment to less than 1 % at the end of deep cryogenic treatment. Increase in hardness from 67 HRC to 69.5 HRC and increase in impact energy from 5.2 J/mm2 to 5.4 J/mm2 were observed at the end of cryogenic treatment. Sliding abrasion wear study was conducted using pin on disc wear tester. Wear rate of conventionally heat treated samples was found to be as high as 3.18 times deep cryogenic treated specimens. Analysis of SEM images of microstructure confirms presence of ultrafine carbides of size less than 0.2 μ in specimens subjected to cryogenic treatment. Increase in M23 C6 carbides, primarily chromium carbides, along grain boundaries was confirmed by microstructure analysis. SEM images of fractured surface of impact test specimens confirm that cryogenic treatment has not affected the toughness of specimen. The material exhibits an excellent hardening response to cryogenic treatment with increase in hardness and wear resistance.

Keywords: Cryogenic Treatment, Microstructure, Hardness, Wear Resistance, Fractography.

Article published in International Journal of Current  Engineering  and Technology, Vol.3,No.4(Oct- 2013)