Influence of titanium nitride addition on the microstructure and mechanical properties of TiC-based cermets J. Russias a, * , S. Cardinal a , Y. Aguni a , G. Fantozzi a , K. Bienvenu b , J. Fontaine c a Groupe d’Etudes de Me ´tallurgie Physique et de Physique des Mate ´riaux (GEMPPM), Institut National des Sciences Applique ´es de Lyon (INSA), ba ˆ timent Blaise Pascal, 20 Avenue A. Einstein, 69621 Villeurbanne Cedex, France b La Ce ´ramique Plastique, Zone industrielle, 13, rue de Montre ´al, 74100 Ville-la-Grand, France c Laboratoire de Tribologie et de Dynamique des Syste `mes, Ecole Centrale de Lyon, 36 Avenue Guy de Collongue, 69134 Ecully Cedex, France Received 11 November 2004; accepted 5 May 2005 Abstract In this paper, the TiC-based cermets with addition of TiN were fabricated by a conventional powder metallurgy process. The titanium nitride (TiN) and titanium carbide (TiC) used as starting powders have been synthesized by the self-propagating high tem- perature synthesis (SHS) method. This exothermic reaction, easy to process, allows to obtain fine and original powders from low- cost raw materials. Cermets obtained by sintering powders of TiC and Mo 2 C with nickel binder phase are investigated. The effect of TiN adding on the microstructure and the mechanical properties of these composites are studied. Microstructures have been observed by scanning electron microscopy (SEM). Room temperature mechanical properties such as YoungÕs modulus, fracture toughness and microhardness have been measured and related to morphology and chemical composition of the samples. Tribolog- ical experiments were also performed and the friction coefficient of a cermet containing titanium nitride was compared with that of other hard materials. The SHS starting powders used present some particularities, as it was shown in a previous study [Mate ´riaux a ` base de carbures et nitrures, pour coupe et usure, obtenus a ` partir de poudre SHS, PhD Thesis, INSA Lyon, 2004]. The purpose of this work is to show that results concerning the impact of TiN addition on microstructure and mechanical properties obtained on bulk specimens, from these original starting powders, are similar to the ones obtained on alloys from commercial starting powders. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: TiC-based cermets; SHS; Microstructure; Microhardness; Toughness 1. Introduction TiC–Ni-based cermets have been considered as a sub- stitute for the conventional WC-based hard metals as cutting tool materials. First TiC–Ni materials were com- posed mainly of titanium carbide, molybdenum and nickel. Unfortunately they were too brittle [2]. In the 1970s, many studies were carried out to study nitrogen introduction into TiC–Ni–Mo cermets to im- prove their performances by modifying microstructures, especially the grain size of the hard materials. Nowa- days, titanium nitride (TiN) modified titanium carbide (TiC) based cermets are widely used as cutting tools be- cause of their excellent wear resistance and toughness which are better than those of TiC–Mo 2 C–Ni cermets [3–5]. Hardness increases with TiC contents. Molybde- num is generally added as Mo 2 C in order to obtain a good wetting of ceramic phase by the metallic binder, forming a mixed carbide rim (Ti, Mo, C) around TiC grains. Nickel is responsible for a better toughness. Upon sintering, this original compound gives rise to a complex microstructure with the formation of the char- acteristic core–rim structure of the (Ti, Mo)(C, N) International Journal of Refractory Metals & Hard Materials 23 (2005) 358–362 www.elsevier.com/locate/ijrmhm 0263-4368/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.ijrmhm.2005.05.008 * Corresponding author. E-mail address: jmrussias@lbl.gov (J. Russias).