The Mössbauer Spectroscopy Studies of Cementite Precipitations during Continuous Heating from As-Quenched State of High Carbon Cr-Mn-Mo Steel
J. Krawczyk a, P. Bała a and A. Hanc b a AGH University of Science and Technology, Faculty of Metals Engineering and Industrial Computer Science, al. Mickiewicza 30, PL-30-059 Kraków, Poland b Institute of Materials Science, Silesian University, Bankowa 12, 40-007 Katowice, Poland
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Received: 08 06 2008
This work complements the knowledge concerning the kinetics of cementite precipitation during tempering. Investigations were performed on 120MnCrMoV8-6-4-2 steel. The samples of investigated steel were austenitized at the temperature of 900ºC and quenched in oil. Then four of five samples were tempered. Tempering consisted of heating the samples up to chosen temperatures at the heating rate of 0.05ºC/s and fast cooling after reaching desired temperature. This work presents the results of investigations performed carried out using the Mössbauer spectroscopy technique and their interpretation concerning cementite nucleation and growth during tempering. The values of hyperfine magnetic field on 57Fe atomic nuclei, determined for the third component of the Mössbauer spectrum as regards to its intensity, indicate that these are the components coming from ferromagnetic carbides. Big differences in hyperfine magnetic fields coming from Fe atoms existing in the structure of carbides, measured on samples heated up to the temperatures of 80ºC and 210ºC, in comparison with values for 57Fe atoms precipitated from carbides during heating up to the temperature of 350ºC and 470ºC, allow to state that these are the carbides of different crystal structure. The influence of hardened steel heating temperature on cementite precipitation was determined. The Mössbauer spectroscopy was applied not only for magnetic hyperfine fileld studies, but also to analyze the values of quadrupole splitting and isomeric shift, which resulted in significant conclusions concerning the changes in cementite precipitations morphology, chemical composition and the level of stresses being present in this research.
DOI: 10.12693/APhysPolA.114.1651
PACS numbers: 76.80.+y, 31.30.Gs, 75.50.Bb