New production of TiCxN1−x-based cermets by one step mechanically induced self-sustaining reaction: Powder synthesis and pressureless sintering

Chemical Engineering Journal

Gotor

2012

A set of powdered cermets based on (Ti, Ta, Nb)C x N 1-x carbonitride solid solutions were synthesized from mixtures of elemental powders by a mechanically induced self-sustaining reaction (MSR) method and subsequently sintered using a pressureless method. Differing nominal compositions of the hard phase were used, and the nature of the metallic-binder phase (Co, Ni, or Co-Ni) was varied. For comparative purposes, the design of the material was performed using two different synthesis pathways. The composition and microstructure of the ceramic and binder phases before and after sintering were analyzed and related to the microhardness of the material, which was found to increase with increasing contiguity of the hard phase and with decreasing particle size. The samples synthesized in one step (SERIES 2) showed higher microhardness and a more homogeneous microstructure with smaller particle size of the hard phase due to the presence of Ti, Ta, and Nb in the molten binder that hindered the ceramic growth during the liquid phase sintering.

Section: Powdered Cermets Synthesismentioning

confidence: 85%

Development of multicomponent–multiphase materials based on (Ti,Ta,Nb)CxN1−x carbonitride solid solutions

Córdoba

Chemical Engineering Journal

Gotor

2012

“…This reactive milling method uses the strong exothermic character of the carbide and nitride formation from the elements to obtain complex carbonitrides with high purity and with good control of stoichiometry. The same authors have also shown that this methodology may be successfully used in the development of cermets with the basic Ti(C,N)-Ni/Co composition [25].…”

Section: Introductionmentioning

confidence: 99%

Inverse core–rim microstructure in (Ti,Ta)(C,N)-based cermets developed by a mechanically induced self-sustaining reaction

International Journal of Refractory Metals and Hard Materials

Córdoba

Sayagués

et al. 2012

Self Cite

Cermets with a nominal composition (Ti 0.8 Ta 0.2 C 0.5 N 0.5 -20 wt% Co) were synthesised by a mechanically induced self-sustaining reaction (MSR) process from stoichiometric elemental powder blends. The MSR allowed the production of a complex (Ti,Ta)(C,N) solid solution, which was the raw material used for the sintering process. The pressureless sintering process was performed at temperatures between 1400 ºC and 1600 ºC in an inert atmosphere. The microstructural characterisation showed a complex microstructure composed of a ceramic phase with an unusual inverse core-rim structure and a Ti-Ta-Co intermetallic phase that acted as the binder.

“…Typically, cermets consist of titanium carbide (TiC) or titanium carbonitride (Ti(C,N)) ceramic particles embedded in a Co/Ni metal alloy that acts as a binder [2][3][4][5]. Cermets combine the advantages of ceramics and metals [3]; the ceramic phase must mainly provide hardness and wear resistance, whereas the binder phase provides fracture strength and impact resistance [6].…”

Section: Introductionmentioning

confidence: 99%

“…The presence of intermetallics in cermets, which precipitate during cooling, is not a new phenomenon [2,29,30] and has been associated with the excessive dissolution of the ceramic particles in the molten binder, causing Ti enrichment. Although some authors have shown that ductile intermetallic alloys, especially aluminides, are good candidates for binders because the mechanical properties of cermets can be retained at high temperature [31,32], the formation of brittle intermetallics during sintering, such as Ti x Ta 1-x Co 2 , can be extremely harmful for cermets, greatly damaging the fracture strength and toughness [8].…”

Section: Introductionmentioning

confidence: 99%

Toughening of complete solid solution cermets by graphite addition

Chemical Engineering Journal

Torres

Sayagués

et al. 2015

Self Cite

Abstract(Ti 0.95 Ta 0.05 )(C 0.5 N 0.5 )-Co complete solid solution cermets (CSCs) were developed by a mechanochemical synthesis process and a pressureless sintering method. The effect of different percentages of graphite used as a sintering additive on the nature of the binder phase and the mechanical properties of the cermets was investigated. Microstructural and mechanical characterisations were carried out by X-ray diffraction, optical microscopy, scanning electron microscopy, transmission electron microscopy, energydispersive X-ray spectroscopy, Vickers hardness, indentation fracture toughness and nanoindentation. The addition of graphite modified the carbon activity during sintering, reducing the dissolution of carbonitride ceramic particles into the molten binder. The amount of Ti and Ta remaining in the binder after sintering gradually decreased as the amount of graphite added increased, which induced a change in the nature of the binder phase. When no graphite was added, the binder consisted of the brittle Ti x Ta 1-x Co 2 intermetallic phase. With the increase in the amount of graphite added, the formation of more ductile phases, such as Ti x Ta 1-x Co 3 and -Co, was observed, causing a significant improvement in the toughness of the cermets.