Influence of deep cryogenic treatment on microstructure and evaluation by internal friction of a tool steel

The Influence of deep cryogenic treatment (DCT) on microstructure of a tool steel was studied by means of in situ obviation and carbon extraction replica technique. The results obtained have been shown that the retained austenite is present in a thin film between the laths of martensite and stably exists even during prolonged soaking time in liquid nitrogen. The in situ obviation and carbon extraction replica shows the carbides were not precipitated directly in the process of deep cryogenic treatment. The internal friction indicates the carbon atoms segregate to nearby dislocations and produced strong interactions, including interstitial carbon atoms themselves and between the interstitial carbon atoms with time-dependent strain field of dislocations. The cluster of carbon atoms nearby the dislocations either act as or grow into nuclei for the formation of carbide on subsequent during tempering.