Title: The influence of the heat treatments on the nitriding of steels

Authors: G. Scavino, M. Rosso, G. Ubertalli, A. Balzarotti

Addresses: Dipartimento di Scienza dei Materiali ed Ingegneria Chimica, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Torino, Italy. ' Dipartimento di Scienza dei Materiali ed Ingegneria Chimica, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Torino, Italy. ' Dipartimento di Scienza dei Materiali ed Ingegneria Chimica, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Torino, Italy. ' TTN Trattamenti termici Nervianesi, Via I maggio 30, 20014 Nerviano (Milano), Italy

Abstract: Extensive experiments have allowed to assess the influence of previous treatments upon the hardness characteristics of UNI 41CrAlMo7 and UNI 45CrMo5 steels nitrided using three atmospheres with increasing nitrogen fugacity. Normalizing, normalizing plus quenching and tempering, normalizing plus double quench and tempering were tested. Samples solely normalized exhibited the largest degree of surface hardening, whereas double quench and temper caused the most limited hardening effect more visible in the case of the A1 free steels. The latter steel is more sensible to nitrogen fugacity increases. The interrelation between the degree of carbide formation in the matrix during prior massive heat treating and the consequent matrix depletion of nitride forming elements has been seen as the cause of the different hardnesses determined after various massive and surface heat-treating combination.

Keywords: nitriding; hardness profile; heat treatment; normalizing; quenching; tempering; double quench; alloying elements; nitrogen diffusion; top layer; carbide; matrix depletion; steel.

DOI: 10.1504/IJMPT.1993.036540

International Journal of Materials and Product Technology, 1993 Vol.8 No.2/3/4, pp.290 - 302

Published online: 04 Nov 2010 *

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