TiC-based Cermets Research Articles

Influence of sintering techniques on the performance characteristics of steel-bonded TiC-based cermets

This paper analyses the influence of sintering technology (temperature, gas compression during sintering) and heat treatment on the performance of an advanced TiC-based cermet developed for metalforming. The performance was evaluated by adhesive wear resistance, trans- verse rupture strength and microstructure studies. Optimal technology and parameters, ensuring maximum wear resistance and strength of the TiC-based (carbide) composite, are determined. The positive effect of gas compression during sinterin g on the performance of TiC-based cermets was revealed. Heat treatment (tempering) that causes no noticeable changes of strength and hardness results in a remarkable decrease of the adhesive wear resistance.

Boronizing of nano-TiN modified TiC-based cermets

Abstract Nano-TiN modified TiC-based cermets, namely TiC–TiN–WC–Mo–Ni–C, are treated using a solid powder boronizing method. Microstructure, phase identification, transverse rupture strength, microhardness, and cutting performance of boronized cermets are studied and compared with unboronized cermets. The boronized layers are observed using an optical microscope and a scanning electron microscope. Some borides are detected using X-ray diffraction. Though transverse rupture strength decreases, the microhardness of the boronized layer improves significantly. The unboronized and boronized cermets are tested by dry cutting medium carbon steels (AISI1045). The boronized cermets perform better at the cutting speeds of 200 and 300 m/min, but failed at 400 m/min. The performance increase at cutting speeds of 200 and 300 m/min is due to the higher hardness obtained from boronizing. SEM investigation and EDS analysis shows that granule abrasion, adhesive abrasion, diffusion abrasion, and oxidation abrasion are responsible for flank wear.

Effect of WC Addition on Phase Formation and Microstructure of TiC-Ni Composites

In this research, titanium carbide-nickel (TiC-Ni) composites, with tungsten carbide addition, were fabricated by using a powder metallurgy technique. The TiC-Ni mixtures containing between 0-15 wt. % tungsten carbide (WC), were compacted and then sintered at 1300°C and 1400°C, respectively. The phase formation and microstructure of the WC-added TiC-Ni composites have been investigated by X-ray diffraction and scanning electron microscopy techniques. Mechanical properties of these composites were assessed by an indentation technique. The X-ray diffraction patterns showed no evidence of tungsten rich phases in the sintered WC-added cermets. This indicates that during the sintering process, tungsten carbide particles were dissolved in metallic binder phase (Ni phase) via dissolution/re-precipitation process during liquid phase sintering. The liquid phase formed during sintering process could improve sinterability of TiC-based cermets i.e., it could lower sintering temperatures. The TiC-Ni composites typically exhibited a core-rim structure. The cores consisted of undissolved TiC particles enveloped by rims of (Ti, W)C solid solution phase. Hardness of TiC-Ni composites increased with WC content. Sintering temperature also had a slight effect on hardness values.

Fabrication and properties of TiC-based cermet with intra/intergranular microstructure

An intra/intergranular-type TiC-based cermet acquired by spark plasma sintering (SPS) was reported. Composition and microstructure were studied by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). Results revealed that some added TiN nanoparticles less than 80 nm could be entrapped within TiC grains, others ranged from 50 nm to100 nm distributed at the ceramic grain boundaries and formed an intra/inter-type microstructure finally. Properties testing indicated that the material had higher fracture toughness ( K IC) and transverse rupture strength (TRS) at room temperature. The strengthening and toughening mechanisms were also further discussed, respectively.

Microstructure, mechanical properties and thermal shock resistance of nano-TiN modified TiC-based cermets with different binders

Abstract Microstructure, mechanical properties and thermal shock resistance of TiC-based cermets modified by nano-TiN were studied. The highest transverse rupture strength, fracture toughness and hardness were obtained for the cermets with the compositions 14Mo–20Ni (cermet A), 4Mo–10Co–10Ni (cermet B) and 4Mo–20Co (cermet C), respectively. The quenching-strength method and indentation-quench method were used for studying the thermal shock resistance of nano-TiN modified TiC-based cermets. The results of quenching-strength test denote that the critical temperature differences for sharp decline of residual strength are about 410, 370 and 330 °C for cermets A, B and C, respectively. The results of indentation-quench test show that the micro crack length increases and the micro cracks propagate fast with increasing thermal shock temperature and cycles. The propagation rate of the crack is controlled by the stress intensity of crack tip. Both tests show that cermets with high transverse rupture strength have excellent thermal shock resistance. Thermal shock resistance parameter R and R st calculated are in good agreement with the experimental results.

Combustion synthesis of electrical contact materials

Various electrical contact materials have been obtained by self-sustained high-temperature synthesis (SHS) followed by a hot compression step. The materials studied are TiB2 and TiC-based cermets with a copper or aluminium metal matrix. The density, electrical conductivity, and hardness of the cermets produced in this way were measured. The microstructure of the cermets was analyzed by X-ray diffraction and optical microscopy. The conductivity and hardness of the TiB2 cermets with 40 wt % aluminium are competitive to the properties of common silver refractory metals for contact applications. TiB2 cermets with 40 wt % of copper possess a larger porosity which may be prevented by an increased copper content to reduce the reaction temperature.

Microstructure and fracture toughness of TiC–ZrC–WC–Mo–Ni cermets

Abstract TiC-based cermets have advantages such as lower friction coefficient and higher oxidation resistance compared with WC-based cemented carbides. However, the brittleness is still an unavoidable limitation for their utilizations. Microstructure of TiC– x ZrC–15WC–14Mo–20Ni–1C cermets with different ZrC contents was studied by using X-ray diffractometry (XRD), scanning electron microscopy (SEM) in combination with energy dispersive spectrometer (EDS). The experimental results show that ZrC dissolved in the cermets and formed solid solutions of (Zr, Ti, Mo, W)C. The bright and gray coreless grains have been regarded as beneficial for the toughness of the cermets.

Correlation between surface fatigue and microstructural defects of cemented carbides

The main aim of the present theoretical work is to determine numerical dependence between the geometrical parameter of maximum area of structural defect are a max (proposed by Y. Murakami, 1983) and surface fatigue of cemented carbides. The proposed relations allow making predictions of surface fatigue properties of cemented carbides (WC-Co hardmetals—with 10 wt% Co and 15 wt% Co binder; TiC-based cermets—with 32 wt% Fe/8 wt% Ni and 16 wt% Fe/14 wt% Ni binder) in conditions of sliding, rolling contact and impact cycling loading. Pores are considered being equivalent to small defects. Three comparative defects conditions are distinguished: surface pores, pores just below free surface and interior pores. The Vickers hardness of the binder (as mainly responsible for the fracture mechanism of hardmetals and cermets, due to porosity) is presumed to be the basis of such an assumption. The estimate of this prediction has been done by analyzing the pore sizes using the statistics of extremes. The lower limit of fatigue strength and surface fatigue life can be correctly predicted by estimating the maximum occurring pore size in a critical material volume.

Effect of Mo addition on the microstructure and mechanical properties of ultra-fine grade TiC–TiN–WC–Mo2C–Co cermets

Abstract Effect of Mo addition on the microstructure and mechanical properties of ultra-fine grade TiC–TiN–WC–Mo2C–Co cermets was studied in this work. Mechanical properties such as transverse rupture strength, fracture toughness and hardness were also measured. Results show that the microstructure exists in black core/grey rim structure and white core/grey rim structure, and the microstructure has an obvious trend to become finer with the increase of molybdenum content. When the added Mo exceeds 10%, ultra-fine TiC-based cermet with an average particle size of less than 0.5 μm is obtained, because of the formation of a Mo-rich rim and the improvement of the wettability between ceramic phase and metallic phase. The transverse rupture strength increases with the increase of Mo content, and the maximum values of the hardness and the fracture toughness were found with 10 wt% and 5 wt% Mo addition, respectively.

Spark Plasma Sintering Behavior of Fe-TiC Composite Materials Fabricated by Mechanical Alloying

TiC-based cermets attract much attention because of their excellent wear-resistance, high hardness at high temperature, good chemical stability, superior thermal deformation resistance. Therefore, titanium carbide is mainly used for cutting tools, grinding wheels, coated cutting tips and coated steel tools. In this research, Fe-TiC composite materials were fabricated by spark plasma sintering (SPS) after mechanical alloying. TiH2 and graphite powders were used to synthesize TiC phase. In order to compare the properties of sintered materials using mixture powder (D’AE+TiH2+graphite), commercial TiC powder was mixed with Distaloy AE (D’AE) powder as a same mechanical alloying method. Then, the shape of each mixture powder (D’AE+TiH2+graphite, D’AE+TiC (commercial)) and sintering properties were compared. TiC phase was synthesized by self-propagating high-temperature synthesis (SHS) reaction during spark plasma sintering. It was confirmed by using X-ray diffraction (XRD). Energy dispersive spectrometry (EDS) and Scanning electron microscopy (SEM) were used to observe shape of mixture powders and also sintering properties were examined such as hardness, relative density. In case of sintered material for 10min holding time at 1373K after mechanical alloying for 1 hour with D’AE, TiH2 and graphite, it indicated higher hardness value 49HR-C than a case using D’AE and TiC powder.

Performance of carbide composites for cyclic loading applications

The present study attempts to give deeper insight into the surface damage process of carbide composites such as WC hardmetals and TiC-based cermets in the blanking of sheet metals (in cyclic loading conditions). In addition, it focuses on the relationships between the blanking performance of composites on the one hand and the structure-composition and properties wear resistance, plasticity, fatigue strength on the other hand. The influence of advanced sintering techniques on the performance of carbide composites is estimated. A set of laboratory (abrasive wear, adhesive wear, strength, fatigue) and functional tests (blanking of sheet metals) were performed and the effect of advanced sintering techniques (sinter/HIP) on the properties and microstructure developments during testing was analysed by SEM and XRD.

Performance of Cemented Carbides in Cyclic Loading Wear Conditions

The present study describes the wear and mechanical behaviour of some carbide composites (TiC-base cermets and WC-base hardmetals) in cyclic loading applications (blanking of sheet metal). Adhesive wear as well as fatigue endurance were tested, followed by XRD measurements. The results show that the blanking performance of a carbide composite is dependent on its level of resistance to adhesion wear and fatigue sensitivity. XRD measurement revealed that fatigue damage is preceded by plastic strain in both the ductile binder and the brittle carbide phase.

Abrasive wear performance of carbide composites

This work focuses on the abrasive wear performance of some carbide composites, WC-hardmetals and TiC-base cermets (in particular, composites prospective for metalforming). Wear tests were performed using the dry rubber-rimmed rotary wheel machine (modified ASTM G 65-94 method). The results were compared with those, obtained in ordinary erosion tests related to the mechanical properties and the structure. It was shown, that the abrasive wear of a carbide composite is controlled by its rigidity (resistance to elastic and plastic strain) and depends firstly on fraction, grain size and properties of the carbide phase, and secondly on those of the binder.

Performance of TiC base cermets sintered by different techniques

The performance and structure of some advanced TiC base cermets with Ni steel binder, sintered by different techniques (sintering atmosphere, vacuum level, etc.), prospective for metal forming, were investigated. It is shown that the influence of sintering technology on the performance characteristics of TiC cermets (strength, wear resistance) depends on the composition and structure of their binder. Regarding the performance characteristics (transverse rupture strength and adhesive wear resistance) TiC base cermets with martensitic–bainitic steel binder sintered by optimum techniques demonstrated a marked superiority over those with austenitic binder and particularly over those with Ni alloy.

Functionally Graded TiC-Based Cermets via Combustion Synthesis and Quasi-Isostatic Pressing

Experimental results on the preparation of functionally graded TiC-based cermets obtained by combustion synthesis (also known as Self-Propagating High-Temperature Synthesis, SHS) followed by quasi-isostatic (QIP) pressing in a granulate medium are presented. Pellets of TiC-Fe graded cermets are produced by stacking layers of Ti and C powder mixtures in which the content of a NiFe alloy (50 wt% Ni and 50 wt% Fe) is varied from 5 up to 25 vol %. X-ray diffraction showed that the NiFe alloy did not react with the TiC, thus preserving its special properties. Scanning electron microscopy results show a graded material with pores increasing in size towards the side with the highest ceramic fraction.

Influence of titanium nitride addition on the microstructure and mechanical properties of TiC-based cermets

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 temperature 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 2C 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 Young’s modulus, fracture toughness and microhardness have been measured and related to morphology and chemical composition of the samples. Tribological 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 [Matériaux à base de carbures et nitrures, pour coupe et usure, obtenus à 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.

The milling performances of TiC-based cermet tools with TiN nanopowders addition against normalized medium carbon steel AISI1045

The two milling tools obtained from nearly full dense TiC-based cermets with TiN nanopowders addition, with limited percentage of monophase nickel and biphase nickel–cobalt metal binders, were tested in face milling operations, in the dry cutting of a medium carbon steel (AISI1045). Microstructure and mechanical properties were studied. Wear mechanisms (mainly diffusion and oxidation) were investigated in detail and compared each other in order to better understand key aspects due to thermal wear mechanisms. Comparing tool A with B, under the adopted cutting conditions, the tool A has a better resistance to oxidation deformation in machining medium carbon steel, but lower impact breakage property on the same conditions.

Development of Nano-TiN Modified Cermet Cutter

Nano technology is a new technology and begun in 1980’s. The paper firstly overviews the development of cermet cutter and its general situation in research, and then introduces the inherent properties owned by nano-technology and nano-material. In the end the nano-TiN modified TiC-based cermet cutter is fabricated and the mechanical properties of the developed cutter are also tested and analyzed. In order to study nano-modification effect, both nano-modified cermet and general cermet have been made. The mechanical properties of two kinds of materials are also measured. By comparing the measured datum, it has been indicated that the nano-modified cermet has better mechanical properties and the nano-modification technology is effective. This presents a new way to increase the toughness of cermet cutter.

Cutting and wearing characteristics of TiC-based cermets cutters with nano-TiN addition

This paper deals with cutting and wearing characteristics of nano-TiN-modified TiC-based cermets cutters when cutting normalized and quenched medium carbon steels. Results show that the cermets cutters have much longer endurances than YT15 and YG8 cemented carbides cutters in the tests of cutting normalized steel, especially at lower cutting speed. The main failure model of cermets cutters is wearing. When cutting quenched steel, the failure mode of the cermets cutters changes to chipping under each cutting condition. The cermets cutters also show the advantages in endurance under the conditions of low cutting speed, low feed rate and low cutting depth, but their endurances would drop obviously once each of above parameters is raised to some value.

Wear behaviour, durability, and cyclic strength of TiC base cermets

This article describes the wear and mechanical behaviour of TiC base cermets studied by durability tests, including testing of blanking performance and fatigue endurance. Comparative laboratory trials in the abrasive erosion, sliding, and adhesive wear conditions were conducted and complemented by SEM studies. It was found that the blanking performance (durability during blanking of sheet metals) of a carbide composite (hardmetal, cermet) is controlled by its resistance to adhesive wear, and origin and propagation of fatigue cracks (fatigue damage).