TiC Ceramic Composites Research Articles

Microstructure and properties of in situ TiCP/Mn18Cr2 architecture composites

In situ TiC ceramic particle-reinforced steel matrix composites, typically produced via liquid metal infiltration of unstructured preforms, often demonstrate issues with composite areas being prone to fracture. To address this problem, particles with an average diameter of 3 mm were constructed and used to fabricate preforms. Using the in situ self-generation method, the composites were then synthesised with liquid Mn18Cr2. To control the degree of in situ spontaneous reaction, moderator alloy powders at concentrations of 20, 30, 40 and 50 wt.% were utilised. The results reveal that the TiC particle size in the composites gradually decreases as the moderator concentration in the preform increases, reducing from 1.31 to 0.92 μm. The microhardness and elastic modulus at the composite interfaces are intermediate between those of the TiC ceramic particles and the high manganese steel matrix. The inclusion of millimetre-scale architecture enhances the tensile strength of the composites, with tensile strength gradually increasing as the moderator content decreases. This study offers a comprehensive understanding of how moderator content influences the microstructure and mechanical properties of TiC-reinforced Mn18Cr2 composites, providing valuable insights for the development of high-performance structural materials.

Nano/microstructures and mechanical properties of Al2O3–TiC ceramic composites reinforced with Al2O3@RGO nanohybrids

A simple self-assembly method was applied for the successful synthesis of reduced graphene oxide-encapsulated alumina (Al2O3@RGO) nanohybrids with core-shell structures which were then added as nanofiller into a matrix of Al2O3–TiC to fabricate corresponding ceramic composites. Microstructural analysis revealed that RGO sheets were homogeneously dispersed in the matrix and bonded to grains to form a 3D RGO network. The formed unique structure forced RGO sheets to closely bond and strongly attach to matrix grains, effectively increasing load transfer efficiency and contact surface area between matrix and RGO sheets. Analysis of interface characteristics revealed that the interfacial phase Al2OC was generated by a localized carbothermic reduction process. Based on first-principles calculations, Al2OC interfacial phase was found to contribute to the generation of weak and strong hybrid interfaces in composites. The weak and strong hybrid interfaces could not only effectively promote the transfer of loads from the matrix to RGO sheets but also induce conventional toughening mechanisms. In summary, addition of Al2O3@RGO nanohybrids effectively improved the dispersion level of RGO in ceramic as well as interfacial bonding strength between these sheets and matrix, thereby improving overall mechanical characteristics of Al2O3–TiC ceramic composites.

Nanosecond laser-induced controllable oxidation of TiB2–TiC ceramic composites for subsequent micro milling

Laser-induced controllable oxidation coupled with micro-milling (LOMM) provides a feasible way to machine difficult-to-machine materials such as TiB 2 –TiC ceramic composites. The oxidation mechanism of the material under laser irradiation represents the fundamental issue of LOMM. In this paper, laser-induced controllable oxidation of spark plasma sintered TiB 2 –TiC ceramic composites as the workpiece material was studied. A three-dimensional finite element model was established based on ABAQUS/CAE 6.14 software to simulate the effect of laser parameters on temperature field distribution and was verified by experiments. The influence of laser processing parameters and assisted gas atmospheres on the oxidation behavior of TiB 2 –TiC ceramic composites was investigated. Results revealed that the irradiated temperature which had a significant impact on oxidation behavior, increased with an increment of the laser fluence and decreased with an increment of scanning speed with other laser parameters fixed. In addition, based on experimental analysis, the thickness of the oxide-layer increased with an increase of laser fluence and reduced with increasing laser scanning speed. At a laser fluence of 10.78J/cm 2 and scanning speed of 1 mm/s as well as in an oxygen-rich atmosphere, a loose and porous oxide-layer was produced on the irradiated surface. Cross-section thicknesses of the oxide-layer and sub-layer reached 63 μm and 22 μm, respectively. Moreover, the thickness of the oxide-layer was 22 μm in air surroundings and hardly be found in argon and nitrogen atmospheres under identical laser parameters, which indicated that oxygen content had a significant influence on the oxidation reaction of the material. The products of the oxide-layer were mainly composed of rutile- and anatase-TiO 2 . Furthermore, the hardness of the sub-layer was 9.6 ± 0.7 GPa at a laser fluence of 10.78J/cm 2 and scanning speed of 1 mm/s, which was far lower than that of the substrate with a hardness of 20 ± 0.7 GPa. This study provides a theoretical basis for subsequent micro-milling.

Improved machinability of TiB2–TiC ceramic composites via laser-induced oxidation assisted micro-milling

Low manufacturing efficiency, poor processing controllability and deteriorated surface quality were main challenges in micro-milling high hardness TiB2-based ceramic composites. This research work investigated an innovative hybrid machining method named laser-induced oxidation assisted micro-milling (LOMM) of TiB2–TiC ceramic composites with hardness of 20 ± 0.7 GPa. Oxidation mechanism of the material under laser irradiation was studied. At single pulse energy of 0.275 mJ and scanning speed of 1 mm/s, the irradiated surface in an oxygen-rich atmosphere produced metamorphic layer including loose and porous oxide-layer as well as dense sub-layer with hardness of 9.6 ± 0.7 GPa. In addition, the main compositions of formed oxides were anatase TiO2 and rutile TiO2, which can be easily removed with an extremely low cutting force. For the investigated range of milling parameters, the milling force and the machined surface quality were studied in LOMM of TiB2–TiC ceramic composites. A significant reduction (more than 70%) of milling force during removing the oxide-layer was obtained, compared to that milling of the sub-layer. Besides, a well-machined surface quality was obtained (ap = 2 μm and fz = 0.5 μm/z) with a ductile removal mode, and surface roughness is 146 nm. As a case study, a microgroove having a width of 0.4 mm and an aspect ratio of 2.5 was fabricated successfully using LOMM. As a comparison, under identical cutting parameters conventional micro-milling (CONM) was performed. The results indicated that machined quality of the microgroove and perpendicularity of the sidewall obtained by LOMM were superior to those using CONM. Machining efficiency was also improved significantly by 106% using LOMM, compared to CONM. It confirmed that the LOMM process was an efficient and effective method to machine high hardness ceramic composites.

Fabrication and mechanical properties of Al2O3–TiC ceramic composites synergistically reinforced with multi-walled carbon nanotubes and graphene nanoplates

In this study, Al2O3–TiC composites synergistically reinforced with multi-walled carbon nanotubes (MWCNTs) and graphene nanoplates (GNPs) were prepared via spark plasma sintering (SPS). The effects of the MWCNT and GNP contents on the phase composition, mechanical properties, fracture mode, and toughening mechanism of the composites were systematically investigated. The experimental results indicated that the composite grains became more refined with the addition of MWCNTs and GNPs. The nanocomposites presented high compactness and excellent mechanical properties. The composite with 0.8 wt% MWCNTs and 0.2 wt% GNPs presented the best properties of all analysed specimens, and its relative density, hardness, and fracture toughness were 97.3%, 18.38 ± 0.6 GPa, and 9.40 ± 1.6 MPa m1/2, respectively. The crack deflection, bridging, branching, and drawing effects of MWCNTs and GNPs were the main toughening mechanisms of Al2O3–TiC composites synergistically reinforced with MWCNTs and GNPs.

Effects of TiC content and melt phase on microstructure and mechanical properties of ternary TiB2-based ceramic cutting tool materials

Ternary TiB2–WC–TiC ceramic composites were fabricated by hot-pressed sintering at 1650°C. Sintering additives such as WC, TiC, Mo, Ni and Co were used to create a liquid phase and promote densification. The effect of TiC content, (Mo,Ni) and Co on microstructure and mechanical properties of the ternary TiB2–WC–TiC ceramic composites was presented. Flaw structures such as pores and microcracks reduced as the TiC content increased. Wettability of (Mo,Ni) and Co to TiB2 had a significant influence on the microstructure. The microstructure of these composites showed a typical core/rim structure. The core was TiB2 and the rim was mainly composed of TiC. The relative density, microhardness, flexural strength and fracture toughness of these composites increased as the TiC content increased. Results indicated that ternary TiB2–WC–30wt.% TiC–(Mo,Ni) ceramic composite provided the optimal combination of dense microstructure and mechanical properties, including the relative density of (99.3±0.3)%, the microhardness of 24.8±0.3GPa, the flexural strength of 946.9±24.9MPa, and the fracture toughness of 7.4±0.2MPa·m1/2. The high fracture toughness of ternary TiB2–WC–30wt.% TiC–(Mo,Ni) ceramic composite was due to an intensive coupled mechanism of the near-full density, the typical core/rim structure, crack deflection, crack bridging, crack branching and pull-out by a large number of fine WC grains.

Fabrication of TiB<sub>2</sub>-TiC Composites Optimized by Different Amount of Carbon in the Initial Ti-B-C Powder Mixture

Composites of TiC and TiB2 (TiC-TiB2) were prepared by self-propagating high-temperature synthesis (SHS), using compacted reactant different combinations of Ti, C, and B powders. It is very difficult to densify these materials using conventional sintering techniques. It was found that the chemical reaction between the starting Titanium, boron and carbon particles could be completed at 1200°C producing a pure TiB2+TiC ceramic composite. Various carbon content causes the microstructure of the final products was different.

Study on Machinabilty of Al2O3 Ceramic Composite in EDM Using Response Surface Methodology

Electric discharge machining (EDM) has been proven as an alternate process for machining complex and intricate shapes from the conductive ceramic composites. Al2O3 based electrodischarge machinable Al2O3–SiCw–TiC ceramic composite is a potential substitute for traditional materials due to their high hardness, excellent chemical, and mechanical stability under a broad range of temperature, and high specific stiffness. The right selection of the machining condition is the most important aspect to take into consideration in the EDM. The present work correlates the inter-relationships of various EDM machining parameters, namely, discharge current, pulse-on time, duty cycle, and gap voltage on the metal removal rate (MRR), electrode wear ratio (EWR), and surface roughness using the response surface methodology (RSM) while EDM of Al2O3–SiCw–TiC ceramic composite. Analysis of variance is used to study the significance of process variables on MRR, EWR, and surface roughness. The experimental results reveal that discharge current, pulse-on time, and duty cycle significantly affected MRR and EWR, while discharge current and pulse-on time affected the surface roughness. The validation of developed models shows that the MRR EWR and surface roughness of EDM of Al2O3–SiCw–TiC ceramic can be estimated with reasonable accuracy using the second-order models. Finally, trust-region method for nonlinear minimization is used to find the optimum levels of the parameters. The surface and subsurface damage have also been assessed and characterized using scanning electron microscopy. This study reveals that EDMed material unevenness increases with discharge current and pulse-on time.

Element distribution and phase constitution of Al 2O 3–TiC/W18Cr4V vacuum diffusion bonded joint

Vacuum diffusion bonding between Al 2O 3–TiC ceramic composites and W18Cr4V tungsten-based tool alloy has been carried out by using Ti/Cu/Ti multi-interlayer. Element distribution near the Al 2O 3–TiC/W18Cr4V interface was discussed and fracture morphology was analyzed using electron probe microanalysis. Additionally, phase constitutions of the Al 2O 3–TiC/W18Cr4V joint were determined by X-ray diffraction. The results indicate that Ti-rich layers are formed near both Al 2O 3–TiC and W18Cr4V. The Ti-rich layer near Al 2O 3–TiC helps to wet the Al 2O 3–TiC surface. The Ti-rich layer near W18Cr4V can restrain the formation of Fe–Ti intermetallic compounds in the diffusion transition zone. Residual Cu in the diffusion transition zone can act as a stress releasing zone. The structures of interfacial phases are identified as follows: Al 2O 3–TiC/TiO + Ti 3Al/Cu + CuTi/TiC layer/mixed layer of Fe 3W 3C, Cr 23C 6 and α-Fe/W18Cr4V. The fracture morphology of Al 2O 3–TiC/W18Cr4V joint appears brittle features and the failure occurs within the Al 2O 3–TiC ceramic.

Column-growth mechanisms during KrF laser micromachining of Al2O3–TiC ceramics

This paper aims to contribute to the understanding of column-formation mechanisms in Al2O3–TiC ceramic composites due to processing with excimer laser radiation. The mechanisms proposed in the literature to explain the formation of such columns can be grouped into four categories: hydrodynamic mechanisms, vapour phase deposition mechanisms, spatial modulation of absorbed energy mechanisms, and shadowing mechanisms. In the case of Al2O3–TiC ceramics, the first two types of mechanisms can be excluded because experimental results show that the column core is composed of material in a pristine condition. A theoretical simulation of the spatial modulation of absorbed energy due to radiation reflected from pre-existing topographic artefacts reveals that this mechanism does not explain the fact that columns only grow during the first 100–200 laser pulses and can, therefore, be ruled out. By contrast, predictions of the shadowing mechanism with TiC globules formed during the first laser pulses shielding the substrate and favouring column growth are in semiquantitative agreement with experimental observations.

UV pulsed laser deposition from Al 2O 3–TiC ceramic composites

Ablation of Al 2O 3–TiC targets was performed in ultra high vacuum using a pulsed UV laser (KrF, 248 nm). The ablated material was collected onto Si(1 1 1) substrates to grow thin films. Two sets of experiments were performed with two different fluence values (6 and 15 J cm −2) and, for each set, three different substrate temperatures (approximately 580, 680 and 760 °C). The deposition time was always kept at 50 min. The as-deposited films were investigated by X-ray diffraction (XRD) and Auger electron spectroscopy (AES). Structure and chemical composition studies showed that the films consist mainly of amorphous oxides and that the film composition changes periodically along the film depth.

Fabrication, microstructures and High-Strain-Rate properties of TiC-reinforced titanium matrix composites

TiC ceramic particulate-reinforced titanium matrix composites were fabricated and the resultant densification, microstructure, and static and dynamic mechanical properties were studied. Comparing Ti with TiH2 powders as host materials for TiC ceramic reinforcement by pressureless vacuum sintering, TiH2-started composites showed better sinterability and resistance to both elastic and plastic deformation than Ti-started ones. When TiH2 and TiH2-45 vol.% TiC samples were hot pressed, TiH2 matrices transformed to alpha prime Ti and alpha Ti phase, respectively. It is interpreted that the diffusion of an alpha stabilizer carbon from TiC into the matrix is one of the plausible reasons for such a microstructural difference. The 0.2% offset yield strengths of the hot pressed TiH2 and TiH2-45 vol.% TiC samples were 1008 and 1446 MPa, respectively, in a static compressive mode (strain rate of 1×10−3/s). Dynamic compressive strengths of the samples were 1600 and 2060 MPa, respectively, at a strain rate of 4×103/s.

New double negative and positive temperature coefficients of conductive EPDM rubber TiC ceramic composites

In this paper, we have successfully prepared ethylene–propylene-diene monomer (EPDM)/TiC composites as thermistors, with new double negative and positive temperature coefficients of conductivity (NTCC/PTCC). EPDM composites loaded with 50 phr HAF carbon black and different concentrations of TiC were prepared. This study focuses on the effect of TiC content on the vulcanization process, the network structure and the electrical and thermal properties of EPDM/TiC composites. The effect of TiC on the network structure was evaluated e.g. the curing process, the characteristic time constant during vulcanization, the volume fraction of rubber, gel fraction, interparticle distance between conductive particles, the extent of TiC reinforcement in the rubber matrix and molecular weight between cross-linking through experimental and affine–phantom models. The effects of TiC content on the percolation theory, electrical conductivity, conducting mechanism of conductivity, conducting hysteresis and I– V characteristics were also studied, as well as its TiC on the (NTCC/PTCC), thermoelectric power, dielectric constant and thermal conductivity. Stability and reproducibility of the thermal cycles for heating element applications was tested. Specific heat and the amount of heat transfer by radiation and convection as a function of TiC content was calculated using both the calorimetric technique and a theoretical model. It was proved that TiC improves the network structure, electrical and thermal properties of EPDM composites for practical applications.

Effect of silicon carbide volume fraction on interface reaction in SiC p/Al composites

In the present study, ductile cobalt is introduced into an Al2O3–TiC ceramic to form an Al2O3–TiC ceramic matrix composite using a newly developed chemical deposition process rather than conventional powder metallurgy. Experimental results reveal that this chemical deposition process is an effective method for improving the wetting between ceramic and metal interfaces. The resultant composite exhibits a higher fracture toughness than that without cobalt.

Reaction hot-pressed sub-micro Al 2O 3+TiC ceramic composite

Combustion reaction 3TiO 2+3C+4Al⇒3TiC+2Al 2O 3 has been studied by X-ray diffractometer (XRD), differential scanning calorimeter (DSC) and differential thermal analysis (DTA). The exothermal combustion reaction was observed at a temperature of about 1000°C. Poor wetability between liquid Al and TiO 2 (or graphite) solid particles results in an undesired, inhomogeneous microstructure through direct combustion hot-pressing. In the present work, the reaction 3TiO 2+3C+4Al⇒3TiC+2Al 2O 3 has been modified into two separate steps: (1) room-temperature treatment: 3 TiO 2+3 C+4 Al⇒ amorphous phase ( not identified yet )+ Ti , (2) reaction hot-pressing: amorphous phase + Ti⇒3 TiC+2 Al 2 O 3 . A sudden shrinkage was also observed around 1000°C during reaction hot-pressing. Since no liquid phase appeared during reaction hot-pressing, a high-performance Al 2O 3+TiC ceramic composite with sub-micron grains and homogenous microstructure was manufactured.

XeCl laser ablation of Al 2O 3–TiC ceramics

Al 2O 3–TiC ceramic composites are promising materials for micromechanical components. However, due to their hardness, brittleness and contraction during sintering, they are difficult to shape into high-accuracy parts using conventional forming techniques. Laser micromachining can be an alternative technique to shape this type of materials. Previous work using KrF ( λ=248 nm) excimer lasers showed that micromachining was accompanied by the formation of a thin melted layer of resolidified material and, in certain conditions, a cone-like surface topography. This was explained by the different ablation behaviour of Al 2O 3 and TiC. To verify this assumption, Al 2O 3–TiC, Al 2O 3 and TiC ceramics were processed with a XeCl ( λ=308 nm) excimer laser and their ablation behaviour was investigated. It was found that TiC has a higher ablation rate than Al 2O 3. The experimental results suggest that chemical reactions occur during processing of Al 2O 3–TiC in air and that cone formation can be due to the shielding of laser radiation by the resulting compounds.

Photo- and Cathodoluminescence of Combustion-Synthesized Al2O3–TiC Composites

Photoluminescence and cathodoluminescence spectra of combustion-synthesized Al 2 O 3 -TiC ceramic composites were investigated. At room temperature, these composites stimulated by a 514.5 nm Ar + laser and by an electron beam with energy of 25 keV emit red light of 610 to 804 nm centered at about 696 nm and four visible bands centered at 360, 420, 570, and 700 nm, respectively. Secondary electron images, panchromatic and monochromatic CL images, and micro-elemental analyses by SEM and EPMA revealed that the luminary is corundum involving TiC, The 700 nm band of CL or PL is attributed to the transition between T 1 (et) and 3 T 2 (et) excited states, and the 570, 420, and 360 nm bands of CL to the transitions between 3 T 1 (et) or 3 A 2 (e 2 ), 1 T 1 (et), 1 E(e 2 ) excited states and 3 T 1 (t 2 ) ground state of Ti 2+ in corundum, respectively.

Formation of TiB 2–TiC composites by reactive sintering

TiB 2 and TiC are covalent compounds and possess excellent hardness and corrosion resistance. It is very difficult to densify these materials using conventional sintering techniques. In this study, reactive sintering was used to simultaneously synthesise and densify TiB 2–TiC composites. Solid state diffusion was the chief mechanism involved in the sintering process. Intermediate boride phases were formed and their amount and stability were strongly dependent on the sintering temperature and time. It was found that the chemical reaction between the starting Ti metal and B 4C particles could be complete after sintering at ∼1500°C for 1 h, producing a TiB 2–TiC ceramic composite.

Properties of cobalt-reinforced Al2O3–TiC ceramic matrix composite made via a new processing route

Abstract In the present study, ductile cobalt is introduced into an Al 2 O 3 –TiC ceramic to form an Al 2 O 3 –TiC ceramic matrix composite using a newly developed chemical deposition process rather than conventional powder metallurgy. Experimental results reveal that this chemical deposition process is an effective method for improving the wetting between ceramic and metal interfaces. The resultant composite exhibits a higher fracture toughness than that without cobalt.

A study on the oxidation and carbon diffusion of TiC in alumina–titanium carbide ceramics using XPS and Raman spectroscopy

Diamond-like-carbon (DLC) coated and non-coated alumina–titanium carbide ceramics used in magnetic recording heads were annealed in air and nitrogen atmospheres from 200°C to 800°C. Micro-Raman spectroscopy found that carbon of TiC began to diffuse at 350–400°C in air, but above 400°C in N 2. The lower onset temperature of carbon diffusion in air was due to titanium oxidation. The diffused carbon was amorphous at 350–600°C with mixed sp 2 and sp 3 bonds, and nano-crystalline graphite above 600°C. With increase in annealing temperature, the structure became more graphitic, and the degree of crystallization and crystal size increased. The structure changes with annealing temperature were revealed in Raman measurements by increased ratio of D-band to G-band intensities, shifting of G-band to higher frequencies and reduced relative width of the bands at half-height maximum. In a nitrogen environment, carbon still diffused from TiC to leave elemental Ti. Oxidation of titanium was also observed in air. At temperatures less than 600°C, titanium was oxidised to several states, however, at higher temperatures, only polycrystalline TiO 2 was observed. At 800°C, the products consisted of sub-micron needle-like TiO 2. Al 2O 3–TiC ceramic composites with a 60 Å of DLC coating on the surface effectively protected them from oxidation and carbon diffusion at temperatures below 500°C. DLC coating delayed the onset of carbon diffusion and TiC oxidation.