Spark plasma sintering of TixTa1−xC0.5N0.5-based cermets: Effects of processing conditions on chemistry, microstructure and mechanical properties

Abstract

Nanometric powdered Ti x Ta 1-x C 0.5 N 0.5 -based cermets were fabricated using a mechanically induced self-sustaining reaction and consolidated by spark plasma sintering. Highly dense cermets were obtained, and their chemistry, microstructure and mechanical properties were characterised by X-ray diffraction, scanning electron microscopy, image analysis, microindentation and nanoindentation. The microhardness was found to depend directly on the contiguity and size of the ceramic hard particles.The samples synthesised at the lowest temperature (1150 ºC) exhibited more homogeneous microstructures and smaller ceramic particles and the best combination of microhardness and fracture toughness.

Hot-pressing of (Ti, Mt)(C, N)–Co–Mo 2 C (Mt = Ta, Nb) powdered cermets synthesized by a mechanically induced self-sustaining reaction

“…For this cermet, the reduced amount of binder was not adequate to ensure optimal spreading and penetration of the molten binder in between the ceramic particles, leading to retained porosity as confirmed by the volumetric porosity determined by image analysis of the SEM micrographs. This generally optimal densification is better than that observed in similar cermets sintered by SPS [29], in which a remnant porosity of approximately 3-4% was always detected. Moreover, no loss of molten binder was detected during the HP process, a phenomenon that was observed during SPS when the dwell time or the sintering temperature was increased [29].…”

“…This generally optimal densification is better than that observed in similar cermets sintered by SPS [29], in which a remnant porosity of approximately 3-4% was always detected. Moreover, no loss of molten binder was detected during the HP process, a phenomenon that was observed during SPS when the dwell time or the sintering temperature was increased [29].…”

“…Concerning the binder phase, it was observed that this phase was always composed of intermetallic compounds after HP sintering, as reported in previous studies of similar cermets sintered by pressureless (PS) methods [13,30,31] or spark plasma sintering (SPS) [29]. Based on the Ti-Co binary phase diagram [41] (table 3).…”

“…Moreover, the presence of these refractory metals in the binder phase, as shown later by XEDS-SEM measurements, may be an additional reason for the microstructural inhomogeneities because a higher sintering temperature would be necessary to ensure a homogeneous molten binder. An inhomogeneous microstructure was also found in cermets sintered by SPS [29], likely due to the same reason discussed above, a short dwell time. Applying longer dwell times in both sintering techniques would lead to not only a more homogeneous microstructure but also a significant growth of particle size, reaching a microstructure similar to cermets sintered by conventional PS methods [31].…”

“…A study of an MSR coupled to an advanced sintering technique, spark plasma sintering (SPS), has been previously reported [29]. In this work, the experimental procedure of coupling the MSR and HP techniques to fabricate titanium carbonitridebased cermets was examined.…”