Phase evolution and carbon redistribution during continuous tempering of martensite studied with high resolution techniques

Publication date: 15 December 2017
Source:Materials & Design, Volume 136
Author(s): Annika Vieweg, Erwin Povoden-Karadeniz, Gerald Ressel, Petri Prevedel, Tomasz Wojcik, Francisca Mendez-Martin, Andreas Stark, Jozef Keckes, Ernst Kozeschnik
Using high resolution techniques, such as, 3D atom probe tomography, transmission electron microscopy and synchrotron radiation, the continuous tempering process of a 50CrMo4 steel is analyzed. Differences of continuous heating compared to isothermal holding at certain tempering temperatures are discussed. Focus is laid on in-depth characterization of phase development and carbon redistribution effects, such as, segregation and clustering. The results of this work suggest that segregation is the dominant effect at low temperatures (<150°C), while cluster formation within these segregated areas is prominent at intermediate temperatures (150–250°C). Epsilon carbide is formed during continuous heating with off-stoichiometric chemical composition (270–350°C). It transforms finally into cementite (T>350°C).

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