Experimental verification of segregation of carbon and precipitation of carbides due to deep cryogenic treatment for tool steel by internal friction method

This work presents an internal frictional behavior of cold work tool steel subjected to different heat treatment schedules to get insight related to segregation of carbon and refinement of carbide particles due to deep cryogenic treatment. The temperature dependence of internal friction was used to describe the variation of carbon concentration in solid solution of the martensite matrix in successive tempering steps. The results indicate that the carbon atoms segregated to nearby defects forming atomic clusters producing strong interactions, including interstitial carbon atoms themselves and between the interstitial carbon atoms with time-dependent strain field of dislocations because of lattice shrinking and thermodynamic instability of martensite during the deep cryogenic treatment. The clusters act as and grow into nuclei for the formation of fine carbide particle on subsequent tempering that was verified by analyses of TEM micrographs.