Microstructural Characterization of an AISI D2 Tool Steel Submitted to Cryogenic Treatment

Abstract Recent literature has shown several papers dealing with cryogenic treatments of tool steels. Most of them see an improvement in wear resistance supposedly due to microstructural modifications that occur at cryogenic temperatures. Cryogenic treatments are supposed to modify the way secondary carbides precipitate, obtaining a finer and more homogeneous distribution. Specimens of an AISI D2 tool steel were submitted to different thermal cycles, including cryogenic treatment, and the volumetric fraction of micrometric carbides was determined. The samples were analyzed by scanning electron microscopy and the image analysis was carried out with Image J software. The present work also discusses what is understood about secondary carbides and the modifications that occur with micrometric (from the austenite-carbide field) and nanometric (from the temper of martensite) secondary carbides. No difference was found between the micrometric carbide with and without cryogenic treatment, while some indications were found that the nanometric carbides are refined and more homogeneously distributed after cryogenic treatment.