Microstructure Of TiC Research Articles

Influence of an electric field on combustion synthesis process and microstructures of TiC–Al 2O 3–Al composites

In order to achieve combustion synthesis (CS) of high-density and fine-structured TiC–Al 2O 3–Al composites, the activation of combustion reactions of 3TiO 2–3C–(4 + x) Al system with x ≥ 10 mol was conducted by means of external electric field. During the field-activated combustion synthesis (FACS), liquid Al in excess stoichiometric amount was generated and it infiltrated into the synthesized TiC–Al 2O 3 ceramic matrix with porosities, which directly results in a dense TiC–Al 2O 3–Al composites. The influence of electric field on CS process of the reactive system and the resulting microstructures of TiC–Al 2O 3–Al composites was investigated. The results show that an external electric field can effectively improve the adiabatic combustion temperature of the reactive system. Therefore a self-sustaining combustion of the system can be induced thermodynamically. In the experiments, both practical combustion temperature and propagation velocity of combustion wave were obviously enhanced with increasing field strength, whereas sizes of the synthesized TiC and Al 2O 3 particles were significantly decreased at the same time. Under an electric field of 25 V cm −1, TiC–Al 2O 3–Al composites with a relative density of 92.5% was successfully fabricated through the combustion reaction in the system with x = 14 mol, in which TiC and Al 2O 3 particles possess fine-structured sizes of 0.2–1.0 μm, with uniform distribution in metal Al.

The effect of WC, Mo 2C, TaC content on the microstructure and properties of ultra-fine TiC 0.7N 0.3 cermet

The effect of Mo 2C, WC and TaC on the microstructure and properties of ultra-fine TiC 0.7N 0.3 cermet is studied. A series of cermets of varying nominal composition are prepared with ultra-fine powders, following normal powder metallurgical procedures. The results show that the addition of Mo 2C leads to the appearance of black cores in the ultra-fine cermet, which cannot be seen in medium particle cermet. However, excessive addition will result in the thickening of the rim, and the property goes down; the addition of WC makes the microstructure of TiC 0.7N 0.3–10 wt%Mo 2C–14.5%NiCo cermet more complex, and many white cores appear in it; excessive addition will be detrimental for the hardness and strength of the cermet, and in ultra-fine TiC 0.7N 0.3–14.5%NiCo cermet, the optimum addition level of Mo 2C, WC and TaC is 10, 15 and 7 wt%, respectively.

In situ TiC-reinforced steel composite fabricated via self-propagating high-temperature synthesis of Ni–Ti–C system

Steel matrix composite locally reinforced with in situ synthesis of TiC particulate in the sand mould was fabricated successfully using the self-propagating high-temperature synthesis (SHS) reaction of Ni–Ti–C system during casting. The DTA result indicates that TiC could be formed during the SHS reaction of Ni–Ti–C system and Ni serves as a reactant in the SHS reaction of Ni–Ti–C system. As-cast microstructure of TiC locally reinforced region reveals a relatively uniform distribution of TiC particulates. Ni could be a diluent that might prevent the diffusion of carbon between TiC grains in the process of fabricating the composite. Compared to those of unreinforced steel matrix, the hardness and the wear resistance of the TiC locally reinforced steel composite enhanced 67.6% and 349%, respectively.

Effect of Fe on the phases and microstructure of TiC–Fe cermets by combustion synthesis/quasi-isostatic pressing

Abstract Fully dense TiC–Fe cermets ( x = 10, 20, 30, and 40 wt.%) were produced from Ti–C–Fe powder mixtures by combustion synthesis with quasi-isostatic pressing. The effect of Fe content on combustion temperature, combustion wave velocity, and final product density was investigated. The final product was characterized by XRD, SEM, and TEM. The combustion temperature and wave velocity decreased with increasing Fe content. Product density increased with increasing Fe content (96% at 30 wt.%). X-ray diffraction and transmission electron microscopy (TEM) revealed the final product to contain TiC, Fe phases, lath martensite, and Fe 2 Ti. The TiC particle size decreased with increasing Fe content. In addition, a low density of dislocations was observed in both the TiC particles and Fe binder, indicative of annealing and recrystallization, respectively.

Microstructure of TiC–W cladding on steel in nanoscale

TiC–W clad layer is studied in order to inspect that the interface between TiC and the matrix is bonded effectively. Results show that the crystallographic orientations of good bonding conditions are (2 0 0) TiC//(1 0 1) α-Fe and (0 2 0) TiC//( 1 2 1 ̄ ) α-Fe. The TiC reinforcement particles could not melt fully during cladding; thus, the clad layer was strengthened by the residual particles of TiC. In addition, primary precipitated ferrite surrounded the TiC particle by heterogeneous nucleation during solidification.

放電表面改質膜の結晶構造に関する研究

This study deals with the microstructure of TiC hard layer which is produced by electrical discharge machining with semi-sintered electrode. This technology were developed to improve the wear-proof of cutting tools, molds and dies mainly at the first. But, it was observed that the wear of cutting tools with TiC hard layer by EDM is more shorter than PVD or CVD coated tools under high-loaded cutting conditions. Therefore, there is some limitation to apply to cutting tools in full range. In this reports, some experiment is done to be cleared above mentioned problem by means of characterizing the microstructure of TiC by EDM. The main result of experiments are as follows; (1) The microstructure of hard layer made with semi-sintered electrode exhibits extremely amorphous character-istics with lattice constant a=4.3062A, (2) Comparing with molecule ratio 1:1 of TiC, piled TiC atomic composition shows Tic 0.45. Carbon composition is extremely reduced. Therefore, It is thought that TiC is deposited on the substrate breaking down atomic distribution of electrode. (3) Above mentioned microstructure and grain morphologies were caused by ultra high cooling velocity in discharged crater on substrate. (4) As compared with the TiN coated carbide square end mill tool, EDC tool does not result in a precise coated layer like a CVD or a PVD coated layer, which tends to be relatively shorten in tool life.

Effect of nano-micro TiN addition on the microstructure and mechanical properties of TiC based cermets

In this paper the titanium carbide based cermets with addition of nano-micro titanium nitride were fabricated by conventional powder metallurgy techniques. The microstructure of TiC based cermets with nano-micro TiN addition has been investigated by transmission electron microscope (TEM) and a scanning electron microscope (SEM). Bending strength, fracture toughness and hardness were also measured. Results reveal that mechanical properties do not change monotonously with increasing nano TiN addition. Results also show that nano titanium nitride addition can prevent the coalescence of TiC grains. It is also found that nano TiN is distributed at the interface of TiC/TiC grains and that the growth of TiC grains is impeded by the presence of nano TiN particles and that the result is an increase in mechanical properties.

Microstructural analysis of TiC reinforced ferrous surface composites processed by accelerated electron beam irradiation

The present study aims to analyze microstructures of TiC reinforced ferrous surface composites processed by accelerated electron beam irradiation. Two kinds of powder/flux mixtures, i.e., TiC and (Ti + C) powders with 40 wt% of CaF2 flux, were deposited evenly on an AISI 304 stainless steel substrate, which was then irradiated with electron beam. TiC agglomerates and pores were found in the surface composite specimen processed by irradiation of TiC powders because of insufficient melting of TiC powders. In the specimen processed by irradiation of Ti and C powders having lower melting points than TiC powders, a lot of large TiC carbides were precipitated in the melted region, together with a few TiC agglomerates or pores. This indicated the more effective TiC precipitation obtained from the melting of Ti and C powders, instead of TiC powders. The hardness of the surface composite layer was about two times higher than that of the AISI 304 substrate mainly due to the precipitation of TiC carbides. 2001 Elsevier Science B.V. All rights reserved.

Mechanical properties and microstructure of TiC/amorphous hydrocarbon nanocomposite coatings

Using the techniques of reactive magnetron sputter deposition and inductively coupled plasma (ICP) assisted hybrid physical vapor deposition (PVD)/chemical vapor deposition (CVD), we have synthesized a wide variety of metal-free amorphous hydrocarbon (a-C:H) and Ti-containing hydrocarbon (Ti-C:H) coatings. Coating elastic modulus and hardness have been measured by the technique of instrumented nanoindentation and related to Ti and hydrogen compositions. We show that both metal and hydrogen compositions significantly influence the mechanical properties of Ti-C:H coatings. The microstructure of Ti-C:H coatings is further characterized by transmission electron microscopy (TEM), X-ray absorption near edge structure (XANES) spectroscopy, and extended X-ray absorption fine structure (EXAFS) spectroscopy. XANES spectroscopy and high-resolution TEM examination of Ti-C:H specimens shows that the dissolution limit of Ti atoms in an a-C:H matrix is between 0.9 and 2.5 at.%. Beyond the Ti dissolution limit, precipitation of nanocrystalline B1-TiC cluster occurs and Ti-C:H coatings are in fact TiC/a-C:H thin film nanocomposites. Measurements of the average Ti bonding environment in TiC/a-C:H nanocomposites by EXAFS spectroscopy are consistent with a microstructure in which bulk-like B1-TiC clusters are embedded in an a-C:H matrix.

Microstructure of TiC- and ZrC-Dispersion-Strengthened Coppers Prepared by Application of Mechanical Alloying

Microstructure of TiC- and ZrC-Dispersion-Strengthened Coppers Prepared by Application of Mechanical Alloying

Chemical constitution and microstructure of TiC x coatings chemically vapour deposited on Fe-C substrates; effects of iron and chromium

TiC x coatings were chemically vapour deposited in an industrial reactor on Fe-C substrates with carbon contents between 0.06 and 1.20 wt % C. Electron probe microanalyses showed that significant amounts of chromium and iron were present in the coatings and that chromium was also present in the substrate region adjacent to the coatings. By comparing calculated and measured lattice parameters (corrected for the internal stresses present) it became evident that the chromium was in solid solution in TiC x , whereas the iron was not. This was confirmed by micro Auger electron spectroscopy and X-ray diffraction phase analyses. The carbon to metal ratio,x, of the TiC x coatings decreased with increasing distance to the coating/substrate interface. The effect of iron on the X-ray diffraction line broadening and hardness of the coatings was large (in contrast with the effect of chromium) and increased with increasing distance to the coating/substrate interface because of a decreasing iron particle size. The TiC x crystallite size was small and constant throughout the thickness of the coatings. The chromium present in the substrate region adjacent to the TiC x coatings influenced the microstructure of the substrate by formation of iron, chromium-carbides and reduced the growth rate of the coatings.

Residual stress in coated low-z films of TiC and TiN: II. correlation of residual stress with microstructure

The correlations of the residual stresses with microstructures of TiC and TiN films deposited onto various substrates were examained by means of observations of SEM micrographs, X-ray back-reflected Debye rangs and diffraction line profile of X-ray spectorometer chart. It was found that specimens with lower residual stress generally show sharp line profile and good separation between K α2 and K α2 diffraction peaks in both TiN and TiC films, indicating better crystalline perfection. PVD coated TiC films on Mo and Inconel substrates show poor separation of K α2 and K α2 peaks, namely due to higher residual stresses in comparison with those of CVD coated TiN and TiC films on Mo or Inconel substrate. In CVD TiC/Pocographite system, with film thickness ranging from 10 to 100μm, the grain size increase with increasing the thickness, except 100μm thick specimen which has the smallest grain size in this group. However, the sharpness of diffraction profile is best in 20μm thick film, and worst in 100μm thick film. This is in good correlation with the amount of residual stress.

Microstructure of TiC precipitates in Ti-implanted α-Fe

We demonstrate that Ti implanted into α-Fe (with ∼60 appm C impurity) getters C (along with a lesser amount of N) upon postimplantation annealing and precipitates as TiC. The microstructure of the TiC precipitates is examined with TEM for annealing temperatures up to 860 °C. The precipitate size evolution is discussed in terms of growth, ripening, and dissolution processes. The precipitate size increases with anneal temperature for 1 h anneals. At 700 °C no change in precipitate size is observed for anneal times up to 16 h. At 800 °C, an increase in size is observed for increasing anneal times between 1–64 h, while at 860 °C this increase is thought to occur prior to 1 h and the precipitates are observed to decrease with increasing anneal times between 1 and 4 h. At 800–860 °C, the precipitates have a disk-like shape, and their orientation in the α-Fe matrix can be used to identify two types of interfacial area with different degrees of coherency. The implications of the observed microstructure for studies of trapping of embrittling impurities in α-Fe and for modifying the surface mechanical properties are discussed.

Transmission electron microscopy studies of TiC and VCTiC deposits prepared by activated reactive evaporation

The activated reactive evaporation technique is used for processing carbide alloy coatings on tools. Improved properties of these films can be developed if the relationships between processing parameters, microstructural features and mechanical properties are well understood. The main aim of the present investigation was to characterize the microstructures of TiC and (V,Ti)C films prepared by the activated reactive evaporation process at varying deposition temperatures (550–1000°C) and to relate these features to the hardness. The transmission electron microscopy technique was used for this purpose. Two characteristic and completely different grain morphologies are produced in these films, one at low temperatures (extremely fine grained with grain diameters of about 10 nm) and one at high temperatures (of more normal grain structure with micronsized grains). These are all equilibrium single-phase structures of TiC and (V,Ti)C respectively except for the low temperature deposit of (V-23 at.% Ti)C prepared at 550°C; (V-23 at.% Ti)C is a mixture of TiC, VC and free graphite phases. The hardness is superior in the large-grained structures.