Influence of cyclic temperature changes on the microstructure of AISI 4140 after laser surface hardening

• Published in: Acta materialia Vol. 55; no. 2; pp. 589 - 599
• Main Authors: Mioković, T., Schulze, V., Vöhringer, O., Löhe, D.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 2007; Elsevier Science
• Subjects: Applied sciences; Austenite formation; Chromium molybdenum steels; Cyclic temperature changes; Exact sciences and technology; Hardening; Hardening. Tempering; Heat treatment; High strength steels; Laser hardening; Lasers; Martensitic transformation; Metals. Metallurgy; Microstructural characterization; Microstructure; Process parameters; Production techniques; Pulsed lasers; Quenching and tempering; Structural steels; Surface hardening; Laser hardening; Martensitic transformation; Microstructural characterization; Cyclic temperature changes; Austenite formation; Temperature; Heat treatment; Surface quenching; Temperature effect; Surface treatment; Hardening; Phase transformation; Austenite; Laser; Microstructure
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2006.08.052

In recent years laser surface hardening using pulsed laser sources has become an increasingly established technology in engineering industry and has opened up wider possibilities for the application of selective surface hardening. However, the choice of the process parameters is generally based on experience rather than on their empirical influence on the resulting microstructure, and for hardening processes with cyclic temperature changes, almost no correlations between process parameters and hardening results are known. Therefore, some problems regarding the choice of the process parameters and their influence on the resulting microstructure still remain. In particular, there is a lack of data concerning the effect of cyclic temperature changes on hardening. To facilitate process optimization, this paper deals with a detailed characterization of the microstructures created in quenched and tempered AISI 4140 (German grade 42CrMo4) steel following a temperature-dependent laser surface hardening treatment. The structure properties were obtained from microhardness measurements, scanning electron microscopy investigations and X-ray diffraction analysis of retained austenite.