TiC Grains Research Articles

Characterization of microstructure and tensile fracture behavior in a novel infiltrated TiC–steel composite

The tool steel matrix composite was successfully produced by a novel infiltration method so as to have TiC reinforcement particles more than 57vol.%. The interface between α-Fe and TiC was found to be semi-coherent nature and the orientation relationship was clearly confirmed, i.e. [012]α-Fe//[110]TiC, (200)α-Fe//2¯24TiC. Tensile fractures consisted mainly of {100} microcleavage of TiC grains with no interfacial decohesion. The increased strength of the composite at 700°C is rationalized in terms of mutually interactive influences of load transfer mechanism and the matrix strengthening resulted from the increased density of dislocations.

Survival of refractory presolar grain analogs during Stardust‐like impact into Al foils: Implications for Wild 2 presolar grain abundances and study of the cometary fine fraction

We present results of FIB-TEM studies of 12 Stardust analog Al foil craters which were created by firing refractory Si and Ti carbide and nitride grains into Al foils at 6.05 km s 1 with a light-gas gun to simulate capture of cometary grains by the Stardust mission. These foils were prepared primarily to understand the low presolar grain abundances (both SiC and silicates) measured by SIMS in Stardust Al foil samples. Our results demonstrate the intact survival of submicron SiC, TiC, TiN, and less-refractory Si3N4 grains. In small ( 5 lm) are typically fragmented and are somewhat flattened in the direction of impact due to partial melting and/or plastic deformation. The low presolar grain abundance estimates derived from SIMS measurements of large craters (mostly >50 lm) likely result from greater modification of these impactors (i.e., melting and isotopic dilution), due to higher peak temperatures/ pressures in these crater impacts. The better survivability of grains in smaller craters suggests that more accurate presolar grain estimates may be achievable through measurement of such craters. It also suggests small craters can provide a complementary method of study of the Wild 2 fine fraction, especially for refractory CAI-like minerals.

Preparation of a fine-structured TiC–Co composite by high-energy milling and subsequent heat treatment of a Ti–Co alloy

A fine-structured TiC–Co composite was prepared from a Ti–Co alloy by high-energy milling and subsequent heat treatment. The nanosized TiC and amorphous Co powders were synthesized by mechanical alloying of a Ti–Co alloy/graphite mixture. The amorphous Co phase was crystallized during the subsequent heat treatment. The DSC study revealed that Co in the nanosized TiC–Co powders melts at a lower temperature than that in conventional mixed TiC–Co powders. The coalescence of the nanosized TiC grains was effectively suppressed by the finely-dispersed Co phases making it possible to maintain the fine microstructure throughout the liquid-sintering process. The mechanical properties of the fine-structured TiC–Co composite were superior to not only the conventionally prepared TiC–Co composite but also to the previously reported TiC–Ni composites.

Chip Formation Characterisation and Tem Investigation of Worn PcBN Tool during Hard Turning

The influence of cutting conditions on the chip formation during hard turning of martensitic AISI 440B stainless steel and microstructure of worn PCBN cutting tool using situ lift-out technique, observed using scanning electron microscope (SEM) and transmission electron microscope (TEM) was experimentally studied. The increasing cutting speed affects the formation of shear, localized chips with rapid increase in chip velocity and degree of segmentation at cutting speeds higher than 200 m/min. The SEM and TEM study showed evidences of strong chemical affinity between the work material and PCBN tool. Fe from the work material was found in the vicinity of TiC and AlB grains of the tool with TiC having greater affinity for Fe.

Sintesa dan Karakterisasi Material Ceramic Metal Composite (Ti1-xMox)C-NiCr melalui Proses Pemaduan Mekanik dengan Variasi Komposisi Molibdenum

Powder mixtures of Ti, Ni, Cr and C with various composition of Mo are processed by planetary ball mill for 10 h and subsequently, sintered at temperatur of 1100 C for 2 h have been investigated. The result shows that wettability of titanium carbides enhanced with the fraction of molybdenum. Furthermore, the XRD and SEM observation show that TiC grains are refined, indicating Mo is an affective grain growth inhibitor.

Microstructure and mechanical properties of in situ casting TiC/Ti6Al4V composites through adding multi-walled carbon nanotubes

In this study, multi-walled carbon nanotubes (MWCNTs) were added as carbon sources to fabricate in situ casting TiC/Ti6Al4V (TC4) composites. The effects of MWCNTs on the microstructure and mechanical properties are studied. The composites are analyzed by X-ray diffraction, field-emission scanning electron microscope and electron probe microanalysis. The fracture behavior of TiC/TC4 composites are also studied. Smaller size of TiC particles and grain compared with TC4-graphite composites can be observed. The tensile strength of TC4-MWCNTs composites is about 1110.1MPa, which is higher than that of TC4-graphite composites, about 1003.6MPa. Fracture behavior also was changed by adding MWCNTs in situ casting TiC/TC4 composites.

Comparative analysis of thermal stability of two different nc-TiC/a-C:H coatings

The aim of this work is to compare the thermal stability of two nanocrystalline TiC/a-C:H coatings prepared by magnetron sputtering of titanium target in acetylene containing environment. The coatings exhibited different chemical composition ([Ti]/[C] ratio) and structure. Their thermal stability was studied using thermal desorption spectroscopy in the temperature range from 500 to 1000°C. The hardness and elastic modulus of both coatings remained almost unchanged up to 700°C, however, they substantially differed from the point of view of their fracture resistance. Up to 700°C no indentation induced cracking occurred in the titanium rich coating, however, reaching the annealing temperature of 1000°C, this coating became porous and spontaneous tensile cracking appeared on its surface. On the other hand, the surface of the carbon rich coating did not show any spontaneous tensile or compressive cracking. It remained almost unchanged in the whole studied temperature range. Its resistance against indentation induced cracking gradually decreased with temperature, which was indicated by an increase of the number of cracks inside the residual indentation imprints. The critical depth where the underlying layer started to influence the nanoindentation measurement was found using differential hardness studies. According to XRD tests, the grain size increased for both films already at the first annealing to 500°C. The XRD also proved that in the case of annealed titanium rich film a large transformation of sub-stoichiometric TiC grains into pure Ti grains and more stoichiometric TiC developed. Raman spectroscopy studies showed that after annealing of Ti rich coating at 1000°C there remained no amorphous carbon phase anymore.

Effect of TiC nanoparticles on the microstructure and mechanical properties of gas tungsten arc welded aluminum joints

In the present study, TiC/Al composite fillers of gas tungsten arc (GTA) welding with different contents of TiC nanoparticles were successfully fabricated by accumulative roll bonding (ARB). The purpose of ARB was to create a uniform distribution of TiC nanoparticles in the fillers and to form a good interfacial bonding between the aluminum matrix and TiC nanoparticles. The microstructure, mechanical properties and fracture surface morphology of the welds were investigated. It was found that TiC nanoparticles decreased the grain size of the primary α-Al phase due to the augmented nucleation and retarded growth. The tensile strength and hardness of weld improved with increasing TiC nanoparticle content. The improvement in the mechanical properties was attributed to the uniform distribution of TiC nanoparticles and grain refinement. Therefore, it can be concluded that the TiC/Al composite filler can serve as a suitable filler for GTA welding of aluminum and its alloys.

Incorporation effects of Si in TiCx thin films

Ti-Si-C thin films with varying Si content between 0 to 10at.% were deposited by DC magnetron sputtering from elemental targets. The effects on microstructure and lattice parameters were investigated using x-ray diffraction, x-ray photoelectron spectroscopy, transmission electron microscopy, and first-principles calculations. The results show that the growth of pure TiCx onto Al2O3(0001) substrates at a temperature of 350°C yields (111) epitaxial and understoichiometric films with x ~0.7. For Si contents up to 4at.%, the TiCx epitaxy is retained locally. Si starts to segregate out from the TiCx to column boundaries at concentrations between 1 and 4at.%, and causes a transition from epitaxial to polycrystalline growth above 4at.%. Eventually, the top part of the films form a nanocomposite of crystalline TiC grains surrounded by amorphous SiC and C for Si contents studied up to 10at.%. The results show that Si takes the place of carbon when incorporated in the TiC lattice.

Electrically conductive ZTA–TiC ceramics: Influence of TiC particle size on material properties and electrical discharge machining

Processing of highly abrasive materials via powder injection molding or extrusion requires mold materials with high wear resistance to increase the durability of the tools and to sustain a high quality of the manufactured products. High performance ceramics which exhibit high hardness, bending strength and toughness show the perfect combination of properties for these applications. However they also have the usual drawback that they cannot be economically customized in complex shapes and low quantities, as they are required for tool and mold design. Recent material development enabled EDM of electrically conductive oxide ceramics, the most widespread machining process for machining of hard materials, as an alternative to conventional ceramic manufacturing and hard machining technologies.This study focuses on the influence of TiC particle sizes on material properties and EDM machinability of ZTA–TiC ceramics with 24vol.% TiC, 17vol.% ZrO2 and 59vol.% Al2O3. Fracture toughness, bending strength and electrical conductivity were analyzed for samples produced from TiC powders with particle sizes varying from 0.43μm to 2.54μm. Surface integrity of wire cut samples and feed rate during machining were investigated. It was shown that reducing the size of electrical conductive grains strongly increases the electrical conductivity and slightly decreases mechanical properties. Therefore also the machining characteristics are influenced by TiC grain size. The feed rate increases with decreasing particle size to a maximum at d50=1–1.3μm. Reduction of TiC particle size also leads to significantly decreasing surface roughness after the main cut. Additionally the necessary number of trimming steps to achieve a distinct surface roughness is also minimized for low particle sizes.

New TiC/Co1.5CrFeNi1.5Ti0.5 Cermet with Slow TiC Coarsening During Sintering

New TiC/Co1.5CrFeNi1.5Ti0.5 cermet was developed by exploiting the advantages of the high-entropy alloy (HEA) binder. A much finer grain structure and thus improved hardness–toughness combination were obtained as compared with two traditional binders, Ni and Ni13Mo7. From the coarsening behavior of TiC grains, the coarsening process of TiC in these three binders is diffusion-controlled. The activation energy of TiC + 20%Co1.5CrFeNi1.5Ti0.5 is the highest and that of TiC + 20%Ni is the lowest. The high activation energy of the Co1.5CrFeNi1.5Ti0.5 binder was attributable to its high content of carbon-strong-binding elements, Cr and Ti, and cooperative diffusion and higher packing density of multiple different-sized atoms. Low diffusion coefficient, low surface energy of TiC grains, and low solubility of Ti in the HEA liquid explain the slow coarsening of TiC grains. This study demonstrates that Co1.5CrFeNi1.5Ti0.5 is an excellent HEA binder for TiC cermets.

The influence of microstructural variations on mechanical and tribological properties of low-friction TiC/diamond-like carbon nanocomposite films

TiC/diamond-like carbon (DLC) nanocomposite films were deposited via steered cathodic arc deposition with various C2H2 flow rates (fC2H2) to study the relationship among the molar fraction of DLC ([DLC]) and the structural, mechanical, and tribological properties of the films. The X-ray diffraction results indicate that the crystallite size of TiC decreased from 14.1 to 3.2nm when fC2H2 was increased from 60 to 151sccm. Transmission electron microscopy images show that an elongated TiC grain shape appeared at low fC2H2 values (<100sccm), the long axis of most grains aligned along the growth direction of the film, and the aspect ratio of elongated TiC grains decreased from 3 to 1.6 when fC2H2 was increased from 80 to 100sccm. Furthermore, the structure of film became a nano-dot TiC/DLC superlattice when fC2H2 was increased to 151sccm. Rockwell-C indentation tester results indicate that the Ti–TiN–TiC/DLC nanocomposite layer structure had good adhesion between the substrate and films. The hardness increased from 32.5 to 39.3GPa when fC2H2 was increased from 60 to 80sccm, and then decreased to 25.1GPa when fC2H2 was further increased to 151sccm. The initial increase in hardness was due to grain refinement leading to suppressed multiplication and mobility of dislocations and the subsequent decrease in hardness was due to grain boundary sliding. The toughness was enhanced by the formation of the nanodot TiC/DLC superlattice, as indicated by plasticity calculated from nanoindentation measurements. The friction coefficient decreased from 0.13 to 0.05 with increasing [DLC].

Synthesis of Ti3SiC2-based materials by reactive melt infiltration

In this paper, Ti3SiC2-based materials were fabricated by reactive melt infiltration (RMI), and the effect of carbon and Al on the formation of Ti3SiC2 was discussed. In the infiltration process of Si melt, the existence of carbon in the initial preform is beneficial to the formation of Ti3SiC2. Carbon can react with TiSi2 to form new TiC with more carbon vacancies than the initial TiC, promoting the formation of TiC twins and Ti3SiC2. In the infiltration process of Al–Si alloy, the existence of Al can effectively decrease the twin boundary energy of TiC grains, leading to the formation of TiC twins and nucleation of Ti3SiC2. There is a diffusion–competition process existing between Si and Al melts, leading to a higher Si/Al ratio in the final samples than in the Al–Si alloy. A possible formation mechanism was proposed to explain the final products.

Laminated Composite of Solidified TiC-TiB&lt;sub&gt;2&lt;/sub&gt; Ceramic to 1Cr18Ni9Ti Stainless Steel Achieved by Combustion Synthesis in High-Gravity Field

By combining mechanical activation and combustion synthesis in ultrahigh gravity field, the laminated composite of TiB2based ceramic to stainless steel was achieved in continuously-graded composition and microstructure, and within the Fe-Cr based intermediate Ti-Fe enriched carbides and fine TiB2platelets decreased gradually in size and volume fraction from the ceramic to stainless steel. Because of the sequent presence of thermal explosion, the dissolution of the molten stainless steel to TiC-TiB2liquid, the formation of diffusion-controlled concentration gradient from the ceramic liquid to the alloy liquid, the rapid sequent solidification of the ceramic and the alloy, the laminated composite is achieved in multilevel, scale-span hybrid microstructure that the different-size, different-morphology Fe-Cr alloy phases alternate with TiB2platelets and irregular TiC grains in size from micrometer to micro-nanometer.

The Effect of TiC on the Liquid Phase Sintering of SiC Ceramics with Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; and Y&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Additives

Low fracture toughness of SiC ceramics limits their applications for the low reliability. Inclusion of second ceramic phase improves the toughness of SiC ceramics. In this presentation, SiC ceramics with 5wt% TiC was pressureless liquid phase sintered (LPS) with the additives of Al2O3 and Y2O3 to ~98% theoretical density at the temperature of 1920 °C for 1 hour. The TiC grains were well distributed and good for the uniform distribution of the liquid phase YAG in the SiC matrix, which resulted in the homogeneous microstructure with fine SiC grains. The existence of TiC benefited the formation of elongated α-SiC, which favored the bridging and deflection of cracks so that the fracture toughness was improved to some extent. Because the amount of TiC was so small that the inherent properties of SiC was not degraded. The flexural strength and Vickers hardness maintained similar with the LPS SiC without TiC. The phase compositions detected in the sample were SiC, YAG and TiC. And no solid-solution of SiC and TiC was revealed by the mapping of EDS.

Effect of NiAl content on phases and microstructures of TiC–TiB2–NiAl composites fabricated by reaction synthesis

TiC–TiB2–NiAl composites were fabricated by self-propagating high temperature reaction synthesis(SHS) with Ti, B4C, Ni and Al powders as raw materials. The effects of NiAl content on phase constituents and microstructures were investigated. The results show that the reaction products are composed of TiB2, TiC and NiAl. The content of NiAl increases with the adding of Ni+Al in green compacts. TiB2, TiC and NiAl grains present in different shapes in the matrix, TiB2 being in hexagonal or rectangular shapes, TiC in spherical shapes, and NiAl squeezed into the gaps of TiC and TiB2 grains. With the increase of NiAl content, the grains of TiC–TiB2–NiAl composites are refined, their density and compressive strength are improved, and the shapes of TiC grains become spherical instead of irregular ones. Finally, the fracture mechanism of the composites transforms from intergranular fracture mode to the compounded fracture mode of intergranular fracture and transgranular fracture.

Microstructure Changes of Ti‐Al‐C Films Deposited by Filtered Cathodic Vacuum Arc

Nanocomposite Ti‐Al‐C films were deposited by filtered cathodic vacuum arc (FCVA) at different CH4 flows. The deposited films were characterized in terms of elemental and phase compositions, chemical bonds, and texture as a function of CH4 flow rate by XRD, XPS, HRTEM, Raman spectroscopy, and IR spectroscopy. The results show that the TiC grain size decreases from 4.2 to 2.9 nm as the CH4 flow rate increases from 30 to 80 sccm. The analysis of XPS, HRTEM, and Raman spectroscopy shows that the microstructure of deposited films turns from a TiC dominant TiC‐C film to a carbon network dominant TiAl‐doped a‐C film structure as the CH4 flow increases from 30 sccm to 80 sccm. IR spectroscopy shows that most of the hydrogen atoms in the deposited films are bonded to the sp3‐hybridized C atoms. All the composition and microstructure change can be explained by considering the plasma conditions and the effect of CH4 flow.

Ti&lt;sub&gt;2&lt;/sub&gt;AlC/TiC Functionally Graded Material Fabricated by Reaction Sintering

Ti/Al/TiC mixed powders were used as the raw materials for the fabrication of functionally graded material (FGM) by hot pressing sintering. The sample was analyzed by SEM combined with Metallographic microscope and Energy Disperse Spectroscopy,The results show that each layer is composed of TiC and Ti2AlC, without containing other phases. The size of TiC grains are about 3-6 μm. With TiC content in the layers increasing, Ti2AlC grains gradually decrease. The lathy Ti2AlC grains of the FGM have a length of about 10 μm and a width of about 4 μm. The interface of each layer has a good combination with a certain thickness transition layer.Microhardness tester is used to analyse the hardness of material.The results show that the Vickers hardness of every layer increases with TiC content increasing. The thermal shock performance test found that material has good thermal shock performance.

Fabrication of Multiple Ceramic Particle Reinforced Iron Matrix Coating by Laser Cladding

Multiple ceramic particle reinforced iron matrix coatings were produced by laser beam melting mixture of B4C, TiO2, Al, and Fe-based self-melting powders. The results showed that the coating were mainly composed of α-Fe, TiB2, and TiC. TiB2 grains showed rectangle structures with deep grey, and that TiC grains exhibited near-cubic morphologies with light grey in the coating. The amount, type, and size of the reinforcements were influenced by the content of B4C, TiO2, and Al. Compared to the substrate, wear resistance of the composite coatings were significantly improved. Furthermore, the coatings possessed more effective protection for scratching and plastic deformation.

In Situ TiC Ceramic Particles Locally Reinforced Al‐Si Matrix Composites Prepared by SHS‐Casting Method from the Al‐Si‐Ti‐C System

Using Al‐Si‐Ti‐C powder mixtures, TiC grains locally reinforced Al‐Si matrix composites were produced through self‐propagating high‐temperature synthesis and casting method. The formation of TiC could be ascribed to the dissolution–reaction–precipitation mechanism. The TiC grains were uniformly distributed in the locally reinforced regions of the Al‐Si matrix. With increasing Al‐Si content, the size of TiC grains decreased. No pores and cracks were present at the interface between the Al‐Si matrix and the reinforced regions. Wear resistance of the locally reinforced regions is significantly improved compared with that of the Al‐Si matrix.