Internal Nitriding of Fe-Cr-Mo Alloys; Precipitation of mixed nitrides and role of the Cr/Mo-ratio

Tuesday, October 20, 2015: 9:00 AM
251C (COBO Center)
Mr. Tobias Steiner , Robert Bosch GmbH, Stuttgart, Germany
Dr. Sai Ramudu Meka , Max-Planck Institute for Intelligent Systems (formerly Metals Research), Stuttgart, Germany
Dr. Thomas Waldenmaier , Robert Bosch GmbH, Stuttgart, Germany
Prof. Eric J. Mittemeijer , University of Stuttgart, Stuttgart, Germany
Understanding and controlling the internal precipitation of nitrides during nitriding of technologically important steels allow for tuning of the microstructure and thus the properties of engineering components. The nitrides forming upon nitriding in a Fe-1at.%Cr-1at.%Mo alloy, used as a model alloy for several steel grades based on the Fe-Cr-Mo(-C) system, were characterized detailedly by employing XRD, SEM, TEM, EPMA and Atom Probe Tomography.

Mo-nitride precipitation upon nitriding binary Fe-Mo alloys proceeds very slowly, owing to a large misfit and low chemical driving force. In the present ternary alloy fast precipitation of nanosized, coherent, NaCl-type CrxMo1-xN(x+1)/2 nitrides occurs due to a modest misfit and larger chemical driving force. The fast co-precipitation of Mo and Cr is accompanied by a distinct enhancement of the mechanical properties (as the hardness) and thus suggests the beneficial effect of the presence of both alloying elements upon nitriding of steels based on the Fe-Cr-Mo(-C) system.

See more of: Surface Engineering I
See more of: Technical Program