TiC Grain Size Research Articles

Cermet coatings obtained by electric spark alloying to increase service life of dental instruments

The article presents the results of our study of protective cermet coatings obtained by the method of electric spark alloying on a dental instrument (excavator) using SHS (self-propagating high-temperature synthesis) electrodes based on TiC-NiCr. The influence of discharge energy during electric spark alloying on the roughness, thickness, and proportion of the TiC carbide phase in the cermet coating has been established. It has been shown that during electric spark alloying, the material of the used SHS electrode and the surface of the substrate melt, their convective mixing occurs, and during crystallization, coatings are formed that consist of a strengthening phase TiC and iron-based solid solutions: Fe9.64Ti0.36, F1.88C0.12, and Cr-Ni-Fe-C. It has been found that the maximum size of TiC grains is formed on the surface of the cermet coating, and as they approach the substrate, their size decreases to less than 10 nm. It has been found that the microhardness of the surface of the resulting cermet coatings increased to 6.2 times compared to the microhardness of the original metal base, which was 2 GPa. The results of scanning electron microscopy and energy dispersive analysis of the surface of samples with and without cermet coating before and after corrosion tests are presented. The influence of disinfectants (2 and 100 % Trilox, Wendelin, MegaDes-ortho) on the corrosion resistance of samples with and without developed protective cermet coatings at room and elevated temperatures up to 50 °C and their exposure for 120 h has been established.

Effect of lithium anti-ablation and grain refinement introduced by TiC nanoparticles in LPBF Al–Li alloy

Al–Li alloys are extensively utilized in the field of aerospace due to their low density and high specific strength. However, laser powder bed fusion (LPBF) processed Al–Li alloys still encounter challenges because of hot cracking and Li element ablation. In this study, a TiC nanoparticle modified Al–Mg–Li alloy is developed for LPBF process. Full dense printed TiC modified Al–Mg–Li alloy can be obtained. The presence of TiC nanoparticles in the melt pool effectively increased the viscosity of Al alloy liquid, leading to a reduction in the metal vaporization and liquid spatters, thus preventing the Li ablation during LBPF. The Li content was significantly increased from 0.87 wt.% in the Al–Mg–Li alloy to 1.34 % in the TiC modified Al–Mg–Li alloy. Moreover, the TiC nanoparticles played a key role in transition of columnar to equiaxed grain. The average grain size of TiC modified Al–Mg–Li alloy was refined to about 1.5 μm, two orders of magnitude smaller than that in printed Al–Mg–Li alloy. A gradient transition reaction from TiC to Al3Ti was found on the TiC nanoparticles surface during LPBF. The in-situ formed Al3Ti phase on TiC nanoparticles significantly decreased the lattice mismatch with Al matrix, thereby resulting in an outstanding mechanical property of ultimate tensile strength of 343 MPa and elongation of 9.3 %. The effect of Li element anti-ablation induced by TiC nanoparticles provided a new pathway for additive manufacturing light-weight alloy.

TiC–Fe gradient coating on pure titanium fabricated by in-situ solid-phase diffusion: toward superior hardness and interfacial adhesion strength

Protective hard coatings can significantly improve the bottleneck problem of low hardness and poor wear resistance on titanium alloy surface. However, hardness and adhesive strength usually exhibit an inverse relationship, which greatly limits its widespread use. In this work, TiC–Fe gradient coating with high hardness and adhesion was successfully fabricated by in-situ solid-phase diffusion method (ISDM) on pure titanium at 1000 °C for 2 h. The average thickness of the coating was approximately 5 μm, and the volume fraction of TiC in the coating was greater than 95 vol%. The grain size of TiC gradually increased from 200 nm at the coating surface to 2 μm towards the substrate. The phase interface and the coating/substrate interface exhibited excellent interfacial bonding at the atomic scale. The novel TiC–Fe gradient coating can simultaneously achieve superior hardness (42.9 ± 2.6 GPa) and elastic modulus (557.4 ± 10.3 GPa) that is mainly dominated by in situ synthesised high volume fraction TiC, as well as high adhesion strength (>225 ± 10 MPa). The increased adhesion strength was attributed to the excellent macro/micro interfaces and gradient transition of the microstructure. The use of ISDM to fabricate TiC–Fe gradient coating on titanium alloy may provide a new strategy to improve the comprehensive properties including hardness, elastic modulus, interfacial adhesion strength, and wear resistance for wider applications.

Influence of the sintering temperature on the microstructure, mechanical properties and densification characteristics of (TiB + TiC)/TC4 composite

A hybrid of TiB whiskers and TiC particles reinforced TC4 matrix composites were in situ synthesized by spark plasma sintering (SPS) using a TC4-0.6wt.% B4C powder mixture at temperatures range from 550 °C to 1150 °C. The effect of sintering temperature on microstructure, grain size, mechanical properties and densification process of the (TiB + TiC)/ TC4 matrix composites were investigated. The composite sintered at 1050 °C has the highest tensile strength (1129.0 MPa), yield strength (1077.8 MPa) and plasticity (7.1%). The aspect ratio of TiB whiskers increases almost linearly below 1050 °C and its highest value is 33.2. The grain size of TiC increases with the increase of sintering temperature, and rapid growth occurs in the range of 850 °C to 950 °C. The composite sintered body appears four shrinkage stages before applying sintering pressure. The corresponding peak temperatures are 663 °C, 758 °C, 840 °C and 994 °C, respectively.

The effect of titanium-carbon mixture mechanical activation on SHS pressing parameters and consolidated titanium carbide microstructure

The paper studies the effect of mechanical activation (MA) modes when stirring a stoichiometric mixture of titanium and soot powders in a ball mill on the properties of mixtures, combustion parameters, relative density, and the microstructure of consolidated titanium carbide samples obtained by SHS. MA conditions for Ti + C reaction mixtures in a ball mill were determined. An increase in the mass of grinding bodies activates the MA mechanism. It was shown that the greatest effect from MA was obtained with a two-stage preparation of mixtures: firstly, the titanium powder was activated separately, then the components were mixed together, and this process included not only their mixing, but also soot powder activation. It was found that combustion behavior is affected by the activation of not only titanium, but also soot. After MA of both components, an anomalous increase in the burning rate (more than 100 cm/s) was found on pressed samples. At the bulk density, there was no effect of MA on the mixture combustion process, since in this case the burning rate of all mixtures was in the range of 1.5–2.5 cm/s. It was revealed that MA of reagents for pressed samples leads to an increase in the combustion temperature, an increase in the relative density of the consolidated refractory product to 93–95 %, and a decrease in the average size of TiC grains. A decrease in the residual porosity of consolidated TiC is due to an increase in the hot pressing temperature and plasticity of the product synthesized during the reaction mixture combustion after MA. The main reason is an increase in the exothermic interaction rate. It was shown that MA when mixing reagents makes it possible to control combustion parameters, the microstructure of consolidated products and opens up new opportunities for obtaining refractory materials featuring a unique structure and properties by SHS pressing.

Optimization of microstructure and properties of composite coatings by laser cladding on titanium alloy

Recently, the current technological progress in developing laser cladding technology has brought new approaches in surface modification of titanium alloys. Herein, composite coatings were fabricated by the laser cladding process on Ti811 alloys using a coaxial powder feeding method. A comprehensive study was performed on the laser energy density (Led) and CeO2 content on the structure distribution, microhardness and tribological properties of the coatings. In addition, the growth mechanism of the TiC–TiB2 structure was studied based on the Bramfitt two-dimensional lattice mismatch theory. The results indicated that the phase composition of the coating mainly contained TiC, TiB2, Ti2Ni, and α-Ti. The optimized coating contributed to uniform microstructure distribution and fine grain size when Led was 45 J/mm2 and the CeO2 content was 2 wt%, playing an important role in the best forming quality and properties. Besides, the high matching degree of an interface between TiC (111) and TiB2 (0001) contributed to the TiC–TiB2 composite structure, which positively influenced the grain size and distribution of TiC. The microhardness and wear resistance of the 2Ce coating was dramatically enhanced due to the fine grain strengthening and dispersion strengthening effects of CeO2, contributing directly to generate a high average hardness of 811.67 HV0.5 with a lower friction coefficient.

Effects of Ni content and sintering temperature on the microstructure and mechanical properties of TiC-Ni composites fabricated by selective carburization of Ti-Ni alloys

The effects of Ni content and sintering temperature on the microstructure and mechanical properties of TiC-Ni composites prepared by selective carburization of Ti-Ni alloys were investigated. It was found that coherent boundaries between TiC and Ni were formed after sintering because Ni was attached to TiC in the powdered form. Grain growth by dissolution and precipitation of TiC in Ni was limited during sintering at 1400 °C (below melting point of Ni). As a result, the grain size of TiC did not change with increase in the amount of Ni. However, the grain size of TiC increased with an increase in Ni content at 1500 °C (above melting point of Ni) because the dissolution and precipitation of TiC was promoted in the melted Ni. The fracture toughness (∼18 MPa m 1/2 ) of TiC-Ni composite fabricated at 1500 °C in this study was higher than that (∼11 MPa m 1/2 ) of TiC-Ni composite in the previous study (sintered at 1330 °C) because of effect of the enlarged grains. The hardness was also enhanced by decreasing the content of Ni (13 GPa → 13.5 GPa). Consequentially, it was found that the microstructure and mechanical properties of TiC-Ni composites were customized by controlling the Ni content and sintering temperature in the process suggested in this study. • TiC-Ni with coherent interfaces was fabricated by selective carburization of Ti-Ni. • Grain size increased with increase of Ni by dissolution and precipitation at 1500 °C. • Increase in fracture toughness of TiC-Ni was promoted by the grain growth at 1500 °C. • Decreased hardness of TiC-Ni was compensated by decreasing the amount of Ni. • Customized TiC-Ni was prepared by changing the sintering temperature and Ni content.

Regulated Interfacial Thermal Conductance between Cu and Diamond by a TiC Interlayer for Thermal Management Applications.

The metal/diamond interface consisting of two highly dissimilar materials is widely present in high-power microelectronic devices using a diamond film as a heat spreader or using a metal matrix/diamond filler composite as a heat sink for thermal management applications. To improve the interfacial thermal conductance (G), a common method is to add an appropriate interlayer in between the two materials; however, the effect of the interlayer on G is still not clear. In this work, we prepare a Cu/TiC/diamond structure by magnetron sputtering to detect how the crystallinity, grain size, and thickness of the TiC interlayer influence G between Cu and diamond. We characterize in detail the interface by transmission electron microscopy and X-ray photoelectron spectroscopy and measure experimentally G by the time-domain thermoreflectance technique. The results indicate that the higher crystallinity and thinner interlayer are both beneficial to the improvement of G between Cu and diamond, but the G is insensitive to the grain size of TiC. An increase of G between Cu and diamond as much as 48% can be reached by a highly crystallized 10 nm thick TiC interlayer. The microscopic characteristics of the TiC interlayer have played a decisive role for G between Cu and diamond. While an inserted interlayer in principle has a potential to enhance G between two dissimilar materials, the low crystallinity and large thickness of the interlayer will weaken the enhancement or even reverse this positive effect. The G of a sandwiched structure can be regulated in a wide range by the microscopic characteristics of the interlayer, which provides guidelines for preparation of metal/nonmetal interfaces with high interfacial thermal conductance for thermal management applications.

Effect of Preheating Temperature on the Microstructure and Corrosion Resistance of TiC–Ni Coating by CS/PHIP

TiC–Ni composite coatings with different preheating temperatures were fabricated in situ on the H13 steel substrate by combustion synthesis combined with pseudo-heat isostatic press. The effects of preheating temperature on microstructure, surface porosity, mechanical properties and corrosion behaviour were investigated. The coatings were characterized by XRD, SEM–EDS and microhardness tester. The in situ composite coatings prepared at different preheating temperatures consisted of a network of Ni binder phase (white) and a spheroidal TiC phase (dark) embedded therein. The grain size of TiC, the proportion of the TiC-reinforced phase, surface hardness and interfacial bonding strength increased with increasing preheating temperature. The density and dimension of the AlNi3 phase after the immersion test decreased with an increase in preheating temperature. The corrosion mechanism of the coating was that the Ni binder phase was corroded by aluminium and the TiC phase got oxidized.

Effects of TiC addition on microstructures, mechanical properties and fracture behaviors of porous titanium carbide ceramics

The porous TiC ceramics were prepared by the powder metallurgy-reaction sintering method, in which TiO2, carbon black, phenolic resin and original TiC powder were used as the raw materials. The results indicate that the addition of original TiC powder can affect the microstructures, densities, porosities, mechanical properties and fracture behaviors. With the increase of the TiC addition content, the grain size of secondary TiC, the bulk density and the pore size increase, meanwhile the pore size distribution broadens and the porosity decreases gradually. However, the bending strength does not display a trend of monotone variation, and the maximum bending strength reaches 54.97 MPa when the amount of TiC addition is 30%. In addition, the fracture morphologies of the bending specimens show that the fracture of the secondary TiC grain is usually an inter-granular fracture along the grain boundary. When cracks encounter the original TiC particles, three fracture ways may present, i.e. crack deflection, inter-granular fracture and trans-granular cleavage fracture of the original TiC grains.

Fabrication and Properties of Nano-TiCx/Cu-Cr-Zr Alloy Composites

Nano-sized TiC x /Cu master alloy was prepared by the in situ method of combustion synthesis and hot press consolidation in Cu-Ti- CNTs system. The nano-TiC x /Cu-Cr-Zr alloy composites were fabricated by dispersing the nano-sized TiC x /Cu master alloy into molten Cu-Cr-Zr alloy via stir casting. It was revealed that the average grain size of TiC x /Cu-Cr-Zr alloy composites was significantly refined from 90 μm to 20 μm, the Brinell Hardness of nano-TiC x /Cu-Cr-Zr alloy composites increased from 75.1 HB to 86.8 HB, and the wear resistance increased by 12.6%, compared with the Cu-Cr-Zr alloy. The electric conductivity slightly decreased from 64.71% IACS to 52.93% IACS. The improvements of hardness and wear resistance result from nano-TiC x and grain refinement strengthening.

Ti<sub>2</sub>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.

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.

Effect of Al2O3 content on the synthesized products by the laser ignited self-propagating high-temperature synthesis reaction of Al2O3–Ti–C system

The effect of Al2O3 content on ignition temperature and combustion temperature, the phase composition, the density of the products and the grain size of TiC was investigated by self-propagating high-temperature synthesis reaction of Al2O3–Ti–C system. The results show ignition temperature increases and combustion temperature decreases with the increasing of Al2O3 content; the density of the products varies with Al2O3 content, TiC and Al2O3 are the two stable phases after SHS, TiC particle size decreases with the increasing of Al2O3 content, furthermore, the fracture type of the sintered specimens is a nearly completely intergranular mode.

Grain-size effect on the preferred orientation of TiC/α-C:H thin films

The grain-size effect on the preferred orientation has been revealed in TiC/α-C:H nanocomposite films grown by magnetron sputtering, in which the grain size of TiC can be adjusted through changing C content in films. The finding is that the preferred orientation of films is significantly affected by the grain size, and the crystallographic orientation changes from face-centered cubic (fcc) TiC(111) to (200) as the grain size of nanocrystallite TiC decreases from ∼22.3 to ∼4.7nm. This size-dependent preferred orientation is explained via thermodynamic calculations, from which the size-dependent Gibbs free energies are found to be a key factor that controls the texture development in thin films if the grain size in films is sufficient small.

Consolidation of Binderless Nanostructured TiC by Pulsed Current Activated Sintering and Its Mechanical Properties

A dense nanostructured TiC with a relative density of up to 98% was produced with simultaneous application of 80 MPa pressure and pulsed current of 2800 A using the nanopowder of TiC. The effect of the ball milling times on the sintering behavior, grain size and mechanical properties of binderless TiC was investigated.

A comparative study of TiN and TiC: Oxidation resistance and retention of xenon at high temperature and under degraded vacuum

Dense TiN and TiC samples were prepared by hot pressing using micrometric powders. Xenon species (simulating rare gas fission products) were then implanted into the ceramics. The samples were annealed for 1 h at 1500 °C under several degraded vacuums with PO2 varying from 10−6 to 2×10−4 mbars. The oxidation resistance of the samples and their retention properties with respect to preimplanted xenon species were analyzed using scanning electron microscopy, grazing incidence x-ray diffraction, Rutherford backscattering spectrometry, and nuclear backscattering spectrometry. Results indicate that TiC is resistant to oxidation and does not release xenon for PO2≤6×10−6 mbars. When PO2 increases, geometric oxide crystallites appear at the surface depending on the orientation and size of TiC grains. These oxide phases are Ti2O3, Ti3O5, and TiO2. Apparition of oxide crystallites is associated with the beginning of xenon release. TiC surface is completely covered by the oxide phases at PO2=2×10−4 mbars up to a depth of 3 μm and the xenon is then completely released. For TiN samples, the results show a progressive apparition of oxide crystallites (Ti3O5 mainly) at the surface when PO2 increases. The presence of the oxide crystallites is also directly correlated with xenon release, the more oxide crystallites are growing the more xenon is released. TiN surface is completely covered by an oxide layer at PO2=2×10−4 mbars up to 1 μm. A correlation between the initial fine microstructure of TiN and the properties of the growing layer is suggested.

Consolidation of binderless nanostructured titanium carbide by high-frequency induction heated sintering

The rapid sintering of nanostructured TiC hard materials in a short time was investigated with High-Frequency Induction Heating Sintering process. The advantage of this process is that it allows very quick densification to near theoretical density and prohibition of grain growth in nanostructured materials. A dense nanostructured TiC hard material with a relative density of up to 99% was produced with simultaneous application of 80 MPa pressure and induced current of output of total power capacity (15 kW) within 4 min. The effect of the ball milling times on the sintering behavior, grain size and mechanical properties of binderless TiC was investigated.

Properties and rapid consolidation of nanostructured TiC-based hard materials with various binders by a high-frequency induction heated sintering

The densification of hard TiC–10 vol.% binder (Co, Ni, Fe) materials was accomplished within 2 min using a high-frequency induction heated sintering (HFIHS) method. The advantage of this process is not only rapid densification to almost the theoretical density but also the prevention of grain growth of the nano-structured materials. Highly dense TiC–binder (Co, Ni, Fe) composites with a relative density of up to 99.9% were obtained within 2 min by HFIHS under 80 MPa. The average grain size of TiC in the TiC–10 vol.% Ni composite was approximately 44 nm. The hardness and fracture toughness of the dense TiC–10 vol.% binder (Co, Ni, Fe) composite produced by HFIHS were also investigated.

Nanocomposite TiC/a-C:H film prepared on titanium aluminium alloy substrates by PSII assistant MW-ECRCVD

Thin films of titanium carbide and amorphous hydrogenated carbon have been synthesized on titanium aluminium alloy substrates by PSII assisted MW-ECRCVD with a mirror field. The microstructure, chemical composition and mechanical property were investigated. Using XPS and TEM, the films were identified to be a-C:H film containing TiC nanometre grains (namely, the so-called nanocomposite structure). The size of TiC grains of nanocomposite TiC/DLC film is about 5 nm. The nanocomposite structure has obvious improvement in the mechanical properties of DLC film. The hardness of a-C:H film with Ti is enhanced to 34 G Pa, while that of a-C:H film without Ti is about 12 G Pa, and the coherent strength is also obviously enhanced at the critical load of about 35N.