TiC Phase Research Articles

Study on Nanoscale Friction Behavior of TiC/Ni Composites by Molecular Dynamics Simulations

To systematically investigate the friction and wear behavior of TiC/Ni composites under microscopic, the molecular dynamics (MD) method was used to simulate nano-friction on the TiC/Ni composite. Mechanical properties, abrasion depth, wear rates, temperature change of the material during friction, the microscopic deformation behavior, and the evolution of nickel-based titanium carbide microstructure at high-speed friction have been systematically studied. It was found that the variation of tangential and normal forces is related to the relative position of the grinding ball and the TiC phase, when the grinding ball is located above the TiC phase, large fluctuations in the frictional force occur and extreme value of normal force appears, shallow abrasion depth and low wear rate. During the friction process, there is a high-stress area between the grinding ball and the TiC phase, generating a large number of dislocations. The presence of the TiC phase hinders the development and extension of defects, resulting in a significant increase in temperature. At the same time, dislocation entanglement occurs, which improves the wear resistance of the workpiece. In addition, it was also found that the internal atomic motion guided by the carbonized phase was related to the position of the grinding ball relative to the reinforced phase, with the reinforced phase presenting a tendency to rotate in different directions when the grinding ball was in different positions relative to the reinforced phase, which in turn affected the deformation of the whole workpiece.

INFLUENCE OF TiC CONTENT ON MICROSTRUCTURE AND PROPERTIES OF AlCoCrFeNi HIGH-ENTROPY ALLOY COATINGS PREPARED BY LASER CLADDING

In this study, AlCoCrFeNi-TiCx (x values in molar ratio, x = 0, 0.1, 0.2, 0.3) high-entropy alloy coatings (HEAcs) were prepared on the surface of H13 steel by laser cladding (LC). The microhardness, corrosion resistance, and wear resistance of the HEAcs were analyzed using a microhardness tester, electrochemical workstation, and friction and wear tester, respectively. The results showed that with an increase in the TiC content of the coatings, the interior of the coatings mainly consisted of disordered body-centered cubic (BCC), ordered BCC (B2), and TiC phases, and lattice distortion occurred inside the coatings. TiC was distributed as white particles at the grain boundaries, and the internal microstructure was mainly composed of equiaxed crystals (EC) and petal-like dendrites. The EC were gradually refined owing to the pinning effect. The spinodal decomposition causes a large number of reticulated microstructures inside the grains, and nanoscale TiC precipitation appears in the reticulated microstructures. Owing to lattice distortion and solid solution strengthening, the microhardness of the TiC[Formula: see text] coating was up to 966 HV[Formula: see text], which was approximately 3.2 times that of the substrate. As the TiC content increases, the friction coefficient and mass loss of the coatings gradually decreased, the self-corrosion current ([Formula: see text] gradually decreased and the self-corrosion potential ([Formula: see text] gradually increased. The coatings exhibited good wear and corrosion resistance.

Effect of heat-treatment of Ti/graphite powders on the microstructure and mechanical properties of reactive plasma sprayed TiCN coatings

In this present paper, TiCN coatings were successfully fabricated by reactive plasma spraying, and the effect of heat-treatment of Ti/graphite powders on the microstructure and mechanical properties were studied. Results show that all coatings are consist of ternary TiCN main phase, small amount of TiOx and residual graphite phase. With the Ti/graphite agglomerates heat treatment temperature increasing from 0 °C to 900 °C, the apparent density and flowability of the agglomerates were improved, which is conductive to reduce coating porosity and further improve mechanical properties of sprayed coatings. Although all coatings shows an apparent scattering characteristic for Weibull distribution of Vickers micro-hardness, the coating sprayed using the agglomerates heat-treated at 700 °C exhibits a relatively even distribution. During heat treatment process, Ti particles would react with graphite particle to form TiC phase, especially for the temperature exceed 700 °C. In this case, the amount of ternary TiCN phases in the coatings would increase because of there is more graphite involved in Ti-graphite-N2 reactions. When the heat treatment temperature increase to 900 °C, obvious TiC diffraction peaks are observed in the agglomerates, but this would weak Ti-graphite-N2 reactions and the deposition deformation of the coating. Therefore, the C700 coating presents improved mechanical properties, such as high micro-hardness, good indentation toughness and well wear resistance as compared with other coatings, which is due to its dense microstructure and the relative high amounts of ternary TiCN phase.

Electrical, morphological and structural properties of Ti ohmic contacts formed on n-type 4H–SiC by laser thermal annealing

This work focuses on the obtention of good ohmic contact using laser annealing on a titanium (Ti) layer deposited on n-type 4H–SiC. After the Ti deposition, the contacts were annealed by UV laser irradiation with energy densities ranging from 2.0 to 5.0 Jcm−2 at 30 kHz and 800 mm s−1. Local electrical measurements indicated a uniform current conduction of the irradiated area, independently to the contact topology. A specific contact resistance, determined by circular-TLM patterns, as low as 1.0 × 10−4 Ω cm2 was reached for a Ti layer annealed at 5.0 J cm−2. This value is comparable with a Ti/Ni contact annealed by RTA and is 4 times lower than the one of previous works using Ti laser annealing. The structural investigation demonstrated that the ohmic transition occurs as soon as the TiC phase appears. The improvement of the ohmic properties could be attributed to the preferential alignment onto 4H–SiC of larger and larger TiC grains at the interface. Morphological measurements indicated that the contact surface can be strongly impacted by a high energy irradiation while the contact composition, mainly formed of TiC, is kept once the ohmicity threshold is reached. These results will help to improve the next generation of vertical devices.

Effect of CeO2 on the TiB2 + TiC evolution and water droplet erosion resistance of laser-clad Ni60A coatings

In this study, CeO2-doped Ni60A coating was fabricated on the surface of Ti6Al4V alloys. During the fabrication, heterogeneous nucleation occurred between TiB2 and TiC phases within Ni60A coatings, and the TiB2 + TiC eutectic structure was thereby generated. Ce2O3 phases were formed in-situ by the decomposition of CeO2 powder in the molten pool. On the grain boundary of the CeO2-doped Ni60A coating, Ce2O3 particles were distributed, which inhibited the growth of hard phases TiC and TiB2. Compared with the coating without adding CeO2 powder, the CeO2-doped Ni60A coating had significantly lower crack sensitivity, and the TiB2 phase in the CeO2/Ni60A coating had a far smaller grain size due to the grain refinement effect. In addition, the TiC + TiB2 eutectic structure acted as the skeleton in the coating, enabling the coating to effectively resist the shear effect caused by high-speed water particles. After coating Ni60A and CeO2/Ni60A on the Ti6Al4V alloy, the water droplet erosion depth of the alloy was reduced by 38.7% and 53.2%, respectively. Therefore, adding CeO2 powder into Ni60A coatings has great application value in improving the water droplet erosion resistance of steam turbine blades.

Utilization of L-PBF process for manufacturing an in-situ Fe-TiC metal matrix composite

In-situ Fe-TiC metal matrix composite (MMC) was successfully fabricated via Laser Powder Bed Fusion (L-PBF) using an in-house gas atomized Fe-TiC composite powder. The optimization campaign of printing parameters targeted the maximum density of printed cubic samples. The highest Archimedes density of 7.615 g cm−3 was achieved by laser power of 210 W, scan speed of 763 mm s−1, and hatch spacing of 80 µm corresponding to a volume energy density (VED) of 68.78 J mm−3 given the constant layer thickness of 50 µm. The relative density of the optimized sample was also measured by Computer Tomography (CT) scanning yielding a relative density of 99.85%. According to measured chemical composition and subsequent thermodynamic calculation, the TiC phase can be up to 7.2 vol%, and X-ray diffraction analysis (XRD) confirmed the presence of TiC phase in bcc-iron. Furthermore, Scanning Electron Microscopy (SEM) of sample cross-sections revealed well-dispersed submicron and nano TiC precipitates of two morphologies and size ranges – primary cubic particles (100–400 nm in size) and secondary plate-like particles (up to 300 nm length and below 50 nm width). No micro-cracks and contaminations were detected between the matrix and reinforcement. Electron Back Scattered Diffraction (EBSD) analysis of a cross-section parallel to build direction revealed extremely fine equiaxed grains with a mean size of 1.3 µm which suggests Columnar to Equiaxed Transition (CET). CET and grain refinement were most likely induced by the presence of TiC particles and rapid solidification within L-PBF. Finally, the micro-hardness tests were conducted to evaluate the reinforcement potential of TiC particles. The mean value of 357.0 ± 9.3 HV1 was obtained for the optimized sample which is superior to pure Fe fabricated via L-PBF and a similar MMC fabricated by Electron Beam Powder Bed Fusion (EB-PBF). Furthermore, the microstructure and hardness of the optimized sample was compared to the sample from optimization campaign with the highest coincident VED and relative density. Some micro-defects were observed in the optimized build and their morphologies and origins were discussed.

Effects of SiC on the Microstructure, Densification, Hardness and Wear Performance of TiB2 Ceramic Matrix Composite Consolidated Via Spark Plasma Sintering

Monolithic TiB2 are known to have a good combination of densification and hardness, which are sometimes helpful but limited in application. However, their usage in service at elevated temperatures such as in thermal power plants, cutting tools, tribological purposes (mechanical seals, blast nozzles, wheel dressing tools), etc. leads to catastrophic failure. Hence, the introduction of sintering additives in the TiB2 matrix greatly influences the sinterability and properties (fracture toughness, wear resistance, etc.) of the resulting composite needed to meet the requirement for various industrial applications. In this study, the influence of SiC as sintering additives on the microstructure, densification, hardness and wear performance of TiB2 ceramic was observed. Hence, TiB2, TiB2–10wt%SiC and TiB2–20wt%SiC were sintered at 1850 °C for 10 min under 50 MPa. The impacts of SiC on the TiB2 were observed to improve the microstructure and correspondingly improve the densification and mechanical properties, most especially with the composite with 20wt% SiC. Combined excellent densification, hardness and fracture toughness of 99.5%, 25.5 GPa, 4.5 MPa.m1/2 were achieved, respectively, for TiB2–20wt%SiC. Diverse in-situ phase and microstructural alterations were detected in the sintered composites. It was discovered that the in-situ phase of TiC serves as the contributing factor to the enhanced features of the composites. Moreover, the coefficient of friction and wear performance outcomes of the synthesized composites described a decreased coefficient with an enhanced wear resistance via the increasing SiC particulate. However, applying the load from 10 to 20 N increased the wear rates.

Nanocharacterization of spark plasma sintered TiB2–SiC–graphene composites

This investigation studies TiB 2 –SiC–graphene ceramics in terms of microstructure and mechanical properties. Spark plasma sintering (SPS) at 1800 °C was employed as manufacturing route, and the as-sintered composite was studied using high-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), X-Ray diffractometry (XRD), and nano-indentation. The system was found to be unreactive, and all results dismissed the in-situ nucleation of B 4 C and TiC phases. Although TiO 2 and B 2 O 3 surface impurities were mainly reduced upon the incorporation of graphene nano-platelets (GNPs), the presence of SiO 2 in the final microstructure was confirmed by both XRD and HRTEM methods. The TiB 2 phase achieved a hardness of 35 GPa and a Young modulus of 539 GPa, which were roughly 45% and 25% higher than those measured for the SiC phase. • Microstructure and mechanical properties of TiB 2 –SiC–graphene composite was studied. • TEM, SEM, XPS, EDS, XRD, and nanoindentation tests were used for characterization. • Surface impurities of TiO 2 and B 2 O 3 were reduced by graphene nano-platelets.

Wavy microstructure for improvement of bonding strength in titanium to carbon steel brazed joints

Multi-interlayer composed of Ni and microcracked Cr (MC-Cr), formed by electrochemical deposition, was applied to induce the formation of wavy microstructure enhancing bonding strength of titanium to carbon steel brazed joints with BAg45CuZn filler. Effect of microcrack density in Cr layer on microstructure evolution and mechanical properties of joints has been studied. Phase identification and formation mechanism of joints were analyzed systematically. Introducing multilayer with microcracks avoided the formation of brittle Ti-C and Fe-Ti phases near carbon steel substrate. During bonding, the diffusion of Ti atoms was hindered by compact Cr while promoted by Ni at microcracks. The inhomogeneous diffusion of Ti atoms led to the generation of a wavy microstructure unit that is crater-shaped structure, accompanied by the enrichment of β-CuZn, Fe0.2Ni4.8Ti5 and Cu2TiZn phases. The fracture results showed that these structures improved the shear strength of joints up to 242 MPa by altering the direction of crack propagation.

In-situ formation of Ti-Mo biomaterials by selective laser melting of Ti/Mo and Ti/Mo2C powder mixtures: A comparative study on microstructure, mechanical and wear performance, and thermal mechanisms

• Compare SLM of Ti/Mo and Ti/Mo 2 C powder mixtures to prepare Ti-Mo biomaterials. • Explore thermal mechanisms behind metallurgical differences of Ti-Mo biomaterials. • Reach low moduli in both in-situ Ti-7.5Mo-2.4TiC composites and Ti-7.5Mo alloys. • Reach 12.1% higher strength in Ti-7.5Mo-2.4TiC composites than Ti-7.5Mo alloys. • Reach a 36% lower wear rate in Ti-7.5Mo-2.4TiC composites than Ti-7.5Mo alloys. Ti-Mo alloys/composites are expected to be the next-generation implant material with low moduli but without toxic/allergic elements. However, synthesis mechanisms of the Ti-Mo biomaterials in Selective Laser Melting (SLM) vary according to raw materials and fundamentally influence material performance, due to inhomogeneous chemical compositions and stability. Therefore, this work provides a comparative study on microstructure, mechanical and wear performance, and underlying thermal mechanisms of two promising Ti-Mo biomaterials prepared by SLM but through different synthesis mechanisms to offer scientific understanding for creation of ideal metal implants. They are (i) Ti-7.5Mo alloys, prepared from a conventional Ti/Mo powder mixture, and (ii) Ti-7.5Mo-2.4TiC composites, in-situ prepared from Ti/Mo 2 C powder mixture. Results reveal that the in-situ Ti-7.5Mo-2.4TiC composites made from Ti/Mo 2 C powder mixture by SLM can produce 61.4% more β phase and extra TiC precipitates (diameter below 229.6 nm) than the Ti-7.5Mo alloys. The fine TiC not only contributes to thinner and shorter β columnar grains under a large temperature gradient of 51.2 K/μm but also benefits material performance. The in-situ Ti-7.5Mo-2.4TiC composites produce higher yield strength (980.1 ± 29.8 MPa) and ultimate compressive strength (1561.4 ± 39 MPa) than the Ti-7.5Mo alloys, increasing by up to 12.1%. However, the fine TiC with an aspect ratio of 2.71 dominates an unfavourable rise of elastic modulus to 91.9 ± 2 GPa, 44.7% higher than the Ti-7.5Mo alloys, which, nevertheless, is still lower than the modulus of traditional Ti-6Al-4V. While, TiC and its homogeneous distribution benefit wear resistance, decreasing the wear rate of the in-situ Ti-7.5Mo-2.4TiC composites to 6.98 × 10 −4 mm 3 N −1 m −1 , which is 36% lower than that of the Ti-7.5Mo alloys. Therefore, although with higher modulus than the Ti-7.5Mo alloys, the SLM-fabricated in-situ Ti-7.5Mo-2.4TiC composites can expect to provide good biomedical application potential in cases where combined good strength and wear resistance are required.

Karbon Eklenmiş NiTi Şekil Bellek Alaşımlarının Isı Davranışı ve Mikro Yapısının İncelenmesi

The aim of this study is to perform thermal and microstructural analysis of NiTiC1 and NiTiC2 shape memory alloys (SMAs), produced by arc-melting method. Changing the concentration of Ti and C elements did not change the phase transformation of the alloy as one-stage B2↔B19', but it was observed that the hysteresis temperature, enthalpy, entropy and Gibbs free energies changed depending on the transformation temperatures. Increasing the amount of C element caused a decrease in the grain size and thus a decrease in the elastic energy amount of the alloy. The presence of martensite transformation observed under room temperature in DSC analyzes was not observed in SEM and XRD analyzes taken at room temperature. The presence of B2 austenit, Ni4Ti3 precipitate and TiC phases were detected in XRD analyzes and the presence of these phases was supported by SEM-EDX analysis. Apart from the determined phases, grain boundaries were also clearly seen.

Strengthening and toughening effect of laser melting deposited Nb–16Si–20Ti–3Al with nano-ZrC additions

The phase composition, microstructure, and properties of Laser Melting Deposited (LMD) Nb–16Si–20Ti–3Al alloys with different nano-ZrC (0, 2.5, 5.0, 10.0 wt%) addition were detailed investigated in this study. Results showed that the LMDed Nb–16Si–20Ti–3Al alloy was composed Nb-based solid solution (Nbss) and Nb3Si. The addition of nano-ZrC promoted the decomposition of the Nb3Si phase and the eutectic transformation from Nb3Si to (Nbss+γ-Nb5Si3) eutectic structure. With the content of nano-ZrC increased from 2.5 wt% to 5.0 wt%, the (Nbss+γ-Nb5Si3) eutectic structure was significantly refined. Nb-rich TiC phase precipitated at the grain boundaries of (Nbss+γ-Nb5Si3) eutectic structure by the titanium in the alloy reacted with nano-ZrC additions. With the content of nano-ZrC increased to 10.0 wt%, coarse and irregular primary γ-Nb5Si3 phase and dendritic TiC were observed in the Nb–Si alloy. The fracture toughness was improved from 5.1 MPa m½ to 17.1 MPa m½ by adding an optimized amount of nano-ZrC (5.0 wt%) due to the refinement of (Nbss+γ-Nb5Si3) eutectic structure and dispersion distributed nano-ZrC in the alloys. The Nb–16Si–20Ti–3Al alloy with 5.0 wt% nano-ZrC addition has the maximum compressive strength of 1836 MPa and a compressive strain of 12.6%. The crack deflection seems an important toughening mechanism for Nb–16Si–20Ti–3Al alloys containing nano-ZrC. The fracture mode of each Nb–16Si–20Ti–3Al alloys with (0, 2.5, 5.0, 10.0 wt%) addition exhibited a brittle quasi cleavage fracture.

Microstructure and Tribological Properties of Lubricating-Reinforcing Laser Cladding Composite Coating with the Ti2SC-Ti2Ni Mosaic Structure Phase

Lubricating-reinforcing composite coatings were successfully prepared on Ti6Al4V using laser-clad Ti6Al4V/Ni60/Ni-MoS2 mixed powders with different Ni-MoS2 contents (25, 35, and 45 wt.%), and their microstructure and tribological properties were studied. The reinforcing phase TiC, Ti2Ni, and the lubricating phase Ti2SC were in situ precipitated while Ti2SC and Ti2Ni formed a mosaic coherent structure within the above three coatings. In the 25 and 45 wt.% Ni-MoS2 coatings, the microstructure distribution uniformity of the coatings was not effectively improved by the Ti2SC-Ti2Ni mosaic structure phase due to the lower or higher content of Ti2SC. In the 35 wt.% Ni-MoS2 coating, the forming quality of the coating was the best due to an appropriate amount of the uniformly distributed Ti2SC-Ti2Ni mosaic structure phase. Furthermore, the microhardness of the coatings gradually decreased as the amount of Ni-MoS2 increased. In the 35 wt.% Ni-MoS2 coating, due to the uniformly and diffusely distributed Ti2SC-Ti2Ni mosaic structure phase, the stable lubricating-reinforcing mosaic structure transfer composite films were formed during the progress of the friction and wear tests, which led to the optimal worn surface evenness and quality, the anti-friction and the wear resistance properties compared with the Ti6Al4V, 25 and 45 wt.% Ni-MoS2 coating.

Microstructure and Phase Evolution of Ti-Al-C-Nb Composites Prepared by In Situ Selective Laser Forming.

In the present work, a novel Ti-Al-C-Nb composite was prepared using in situ selective laser forming (ISLF). The formation mechanism of the Ti-Al-C-Nb bulks, which were synthesized using elemental titanium, aluminum, and carbon (graphite) powders via ISLF techniques, was investigated. The results showed that the Ti3Al and TiC phases were the dominant synthesis products during the chemical reactions, and these occurred during the ISLF process. The size of the fine nanoscale crystal TiC grains could reach 157 nm at an energy level of 60 J/mm3. The porous structure of the ISLF specimens was disclosed, and an open porosity of 20–44% was determined via the scanning speed and the laser power. Both the high dynamic viscosity and the reactions of the raw powders led to the generation of a considerable number of pores, whereas the specimen processed using 45 W and 100 mm/s possessed the lowest degree of open porosity.

Enhancing mechanical properties of Ti(C, N)-based cermets via preparation with (Ti, W)(C, N) multi-component powder

Using the traditional preparation method of TiC+TiN powder mixture or simply the Ti(C, N) solid-solution powder to prepare cermet cannot properly avoid the direct contact between TiC, TiN or Ti(C, N) phase and (CoNi) binder phase with undesirable wettability, which is disadvantageous to the strength and toughness of cermet. Here, we introduced a new routine using the (Ti, W)(C, N) solid-solution powder and studied the resultant phase constitutions, microstructures and properties of the Ti(C, N)-based cermets, where the cermets prepared with TiC + TiN + WC and Ti(C, N) + WC were taken as counterparts. The X-ray diffraction (XRD) results showed that regardless of the powder combination, two phases, i.e. fcc-(Ti, M)(C, N) and fcc-(CoNi), were formed, and the lattice constants of these phases varied in different samples, which is attributed to the specific phase stability (TiN > Ti(C, N) > (Ti, W)(C, N) > TiC) calculated based on the CALPHAD (CALculation of PHAse Diagrams) approach. Transmission electron microscopic (TEM) observations further depicted that besides the already-known core-rim structure, the cermet prepared using (Ti, W)(C, N) uniquely incorporated black-gray rimless grains and black-white-gray rimless grains. Two critical mechanical properties, i.e. hardness (H) and fracture toughness (KIC), were subsequently determined using the Vickers indentation method. It was found that the KIC values of the cermet prepared using (Ti, M)(C, N) were improved by 5.1% ~ 29.2% while maintaining the similar level of H as other cermet samples. The segregation of W and Ti in (Ti, W)(C, N) powders led to the formation of cleavage facets in ceramic grains, which could contribute to the hinderance of crack propagation. Eventually, the high-temperature (750 °C) wear tests were conducted to examine the durability of cermet samples. The cermet prepared using (Ti, M)(C, N) generally exhibited enhanced wear resistance, benefiting from the well-balanced H and KIC as well as the restraint of oxidational wear. Thus, this work suggested that preference should be given to (Ti, W)(C, N) solid-solution powders when fabricating high-performance Ti(C, N)-based cermets.

Structural study of W2B obtained via mechanical alloying of W, B4C, TiC and graphite before and after He ions irradiation

• W 6wt.%B 4 C 2wt.%TiC 1wt.%C weight ratio is used in mechanical alloying process. • Sintering at 2550 °C produces nearly single-phase W 2 B (∼98%), WB and TiC (<2%). • Irradiation with 2.5 MeV helium ions to a fluence of 5.0 × 10 20 ion/cm 2 is performed. • Irradiation has negligible effect on the W 2 B main phase content. • All trapped He atoms are found to be located in boron vacancy positions in W 2 B and WB. Elemental powders of W, B 4 C, TiC and C (graphite) in percentage weight ratio of W-–6 wt% B 4 C–2 wt% TiC–1 wt% C are used as precursors in mechanical alloying process aimed at producing tungsten-based material. The composition of the obtained material is nearly single-phase W 2 B (∼98%) with small additions of WB and TiC (<2%), unveiled by XRD analysis. Irradiation with 2.5 MeV helium ions to a fluence of 5.0 × 10 20 ion/cm 2 was performed and the induced radiation damage was assessed. The XRD data unveiled reduction in size of the grains from 300 nm to 260 nm upon the irradiation. It is observed that the irradiation had negligible effect on the W 2 B phase content, while the WB phase content increased by 0.74% and TiC phase content decreased with 0.71% upon irradiation. Raman spectral analysis showed that not only graphite’s carbon is affected by the irradiation, but also the titanium bonded carbon in TiC underwent changes, resulting in development of non-stoichiometric TiC. Positron annihilation spectroscopy is employed for investigating the presence of intrinsic defects and their evolution upon irradiation. Based on the analysis of all the obtained results, we contemplate that the detected WB phase most probably belongs to the grain boundaries of W 2 B grains. The irradiation to a fluence of 5.0 × 10 20 ion/cm 2 did not cause chemical interaction of tungsten boride phases with the carbon species of the material, which would have resulted in the appearance of new phases.

Titanium boride and titanium silicide phase formation by high power diode laser alloying of B4C and SiC particles with Ti: Microstructure, hardness and wear studies

In this work a novel multiphase titanium metal matrix composite (TMMC) coating was developed by high power diode laser assisted alloying of Cp-Ti with the preplaced Boropak powder consisting of B4C and SiC ceramic particles. The XRD, optical microscopy, scanning electron microscopy, EDAX, microhardness and wear testing techniques were employed to investigate structural phase, hardness and wear properties of the alloyed coating. Under the influence of multipass laser alloying, the B4C and SiC ceramic particles decompose to yield boron, silicon and carbon species that react with molten titanium to form TiB2, TiB, TiC and Ti5Si3 phases in the laser alloyed coating. In addition, the un-melted B4C and SiC ceramic particles are dispersed in the titanium matrix. Microstructure of the alloyed coating consists of dendrites and coralline-like structure. The tips of the coralline-like structure are in the range of 150–500 nm. The ceramic multiphase TiB2, TiB, TiC and Ti5Si3 formation resulted in average microhardness around 800–2200 HV0.2 at different regions of the TMMC coating cross section. To correlate the phase formation and microstructural features, surface temperature evolved at the interaction area during laser surface alloying was estimated by a simple equation. Activation energy for the laser melted track was calculated using the Arhennius equation. The linear reciprocating wear test performed on laser alloyed coating against WC ball showed wear rate value of 1.623 х 10−4 mm3/N.m which is 6 times lower compared to the untreated titanium.

Effect of scanning speed on microstructure and properties of TiC/Ni60 composite coatings on Ti6Al4V alloy by laser cladding

The coatings are fabricated with 90 wt% TiC+10 wt% Ni60 powders on Ti6Al4V alloy by laser cladding. The effect of scanning speed on the microstructure and wear behaviors of the coatings is investigated. The results indicate that the clad height decreases with increasing the scanning speed. The clad width and clad depth decrease with increasing the scanning speed. Large-size particles are randomly distributed in the coatings, which are considered to be TiC particles. The microstructure in the coatings changes with the scanning speed by laser cladding. A large number of TiC particles and phases in network structure are observed in the coatings at low scanning speed. The rod and granular TiC particles are exhibited in the coatings at high scanning speed. Some TiC particles are dissolved in the molten pool during laser irradiation heating and then dissolving Ti and C atoms leads to the precipitation of TiC phase during solidification. It is found that the hardness decreases with increasing the scanning speed, whereas the weight loss of the coatings increases. It therefore enhances the wear resistance properties due to the effect of TiC particles.

Effect of phase and elemental composition, structure, and texture of multilayer coatings based on TiCN and TiNbCN on the electrochemical behavior of high-speed steel in 3% NaCl solution

Thin multilayer TiCN and TiNbCN coatings were obtained on a high-speed steel M2 by pulsed magnetron sputtering. The content of N2 and CH4 in the gas mixture was changed to obtain nanostructured layers with different phase and elemental compositions, structure, and texture. The microstructure, defects, and elemental composition of the coatings were investigated using an Ultra 55 field emission electron microscope with an EDX microanalysis system. The phase composition and texture of the coatings were determined using a Shimadzu XRD-6000 X-ray diffractometer with Cu-Kα radiation. Voltammetry and impedance spectroscopy on the coated samples were performed in a 3% NaCl solution. The corrosion behavior of the coatings was characterized by the corrosion current density and polarization resistance (at the corrosion potential). It is shown that the investigated coatings are electrochemically active, and corrosion processes occur not only on the substrate in the discontinuities of the coating but also on the surface of the coating. The TiN-TiCN-TiCN multilayer coating with a maximum content of the three-component phase TiC0.496N0.502, a minimum content of the carbide phase TiC, a maximum texture coefficient, a minimum crystallite size, lower internal stresses and deformations of the crystal lattice has the lowest corrosion current density 0.75 µA cm−2 among the investigated coatings. Niobium improves corrosion resistance, but the presence of a significant amount of the TiC carbide phase in the TiNbCN coating reduces this effect. The morphology of the coating surface after the electrochemical test was studied. The maximum damage of the surface layer is observed for the multilayer TiCN (1) coating.

Sucrose-based sol-gel synthesis of microporous titanium carbide as target material for the production of radioisotopes

An environment-friendly route for the synthesis of titanium carbide by sol-gel processing is reported. The initial solution is prepared via a simple one-pot approach, using titanium isopropoxide and sucrose as molecular precursors under acidic conditions, therefore promoting intimate interactions between the networks of sucrose and of the titanium alkoxide-derived inorganic polymer at the molecular level. Furthermore, the usage of sucrose represents an established and green solution, and provides a viable alternative to the use of toxic compounds. The resulting gels are dried at 120 °C and then undergo carbothermal reduction in Ar atmosphere at different temperatures ranging from 700 °C to 1750 °C. A systematic study of the obtained material is carried out by using FT-IR spectroscopy, X-ray diffraction, Scanning Electron Microscopy, Raman spectroscopy, N 2 physisorption and He pycnometry. The characterization techniques show that the sucrose-derived titanium carbide exhibits a tailored microporous structure and larger specific surface area values compared with those of materials produced using the hazardous phenolic resin-based system. This method thus allows the synthesis of titanium carbide with exquisite textural properties and attractive porous architectures, meeting the requirements for the fabrication of target materials in the field of nuclear medicine, with particular interest in the production and release of scandium radioisotopes. • TiC is proposed as target material for the production of Sc isotopes. • Microporous TiC samples were synthesized via sol-gel chemistry. • Sucrose was successfully employed as an eco-friendly carbon source. • Stoichiometric TiC phase is obtained after carbothermal reduction at 1750 °C. • The material shows larger surface area than that of hazardous-compound-based system.