TiC Layer Research Articles

Fabrication of diamond/copper composite thin plate based on a single-layer close packed diamond particles network for heat dissipation

High-efficiency heat dissipation is crucial for the reliability and durability of high-power electronics devices. Diamond/copper composites have drawn much attention as promising candidate materials for thermal management due to their high thermal conductivity and tunable coefficient of thermal expansion. In this work, a novel method was proposed to fabricate a thin plate of diamond/copper composite based on the construction of single-layer close packed diamond particles network. The composite with a sandwich structure was prepared by press-brazing method, which is cost-effective for both preparation and post-processing. The microstructures of the composite plate containing diamond, AgCuTi filler and Cu were examined. The influence of diamond particle size on thermal conductivity, coefficient of thermal expansion, and mechanical properties were also experimentally measured and theoretically simulated. The results show that a single-layer close packed diamond particles network is densely brazed between copper layers to form a composite thin plate. The interface TiC layer is in-situ formed between diamond and AgCuTi matrix. With increase in the diamond particle size to 1200 μm, thermal conductivity of 552.7 W⋅m−1⋅K−1, coefficient of thermal expansion of 10.1 × 10-6 K−1, and flexural strength of 204.3 MPa are achieved, which are in agreement with the theoretical simulated results. As a heat spreader substrate, the heat dissipation ability of diamond/Cu composite is increased by 5.7 °C in comparison with pure Cu plate. Finite element analysis and testing of actual scenarios further confirm the excellent thermal performance of the sandwich structured diamond/Cu composite thin plate, making it a prospective candidate for thermal management.

Particle distribution and interfacial reaction of WC reinforced titanium matrix composites fabricated by wire and arc additive manufacturing

In this study, preliminary experiments were conducted on wire and arc additive manufacturing (WAAW) with the injection of paraxial WC powder to achieve cost-effective fabrication of titanium matrix composites (TMCs) layers. The results indicated that injecting the powders from the rear of the molten pool did not influence the droplet transfer, and the WC particles exhibited a gradient distribution along the depth of the layer. A strong metallurgical bond formed between the particles and the matrix. The interfacial reaction during the process led to the formation of new phases, including W, W2C, TiC, and (W, Ti)C1-x solid solution. Continuous TiC layers or irregular mixed reaction layers were observed around WC particles. Furthermore, it was found that the W2C layer between WC and TiC may split into many smaller W2C grains.

Surface Hardening of CP Ti by Laser Hardening and Development of Ti/TiC Surface Composite by Laser Sintering Technique for Wear Resistant Surface

This study deals with the hardening of titanium surface by carburising of CP Ti Gr 2 substrate by using laser sintering process. The objective of this project is to harden the surface to improve surface wear resistance of titanium. In this study graphite powder is used as source of Carbon. Carbon from graphite reacts with titanium and TiC layer of 109 micron was measured on the titanium surface. The microstructure and phase analysis results show that presence of only TiC phase on the surface of the titanium substrate. TiC grains are nearly 5 times finer than titanium substrate grains. Grain refinement of TiC phase all over the surface of the substrate resulted in increase in hardness and development of significant wear resistance surface in titanium substrate. Hardness of TiC layer was found to be 2191Hv which is nearly ten times higher than the substrate titanium. Wear test results of pin and disc type shows negligible wear rate as compared to CP Ti substrate. TiC grains are nearly 5 times finer than titanium substrate grains.

Improved creep‐fatigue and remnant tensile/creep properties of 321 stainless steel by self‐healing coating

AbstractAISI 321 steels used as intake valves in turbines are frequently subjected to creep‐fatigue (C‐F) exposure during service. Improving C‐F resistance and assessing remnant creep/tensile properties are therefore required for their safe service. In this work, the self‐healing coating consisting of Al2O3‐13TiO2 layer, TiC layer, and NiCrAlY layer was prepared for 321 steel. The effects of such self‐healing coating on the C‐F and remnant creep/tensile properties were studied. The results showed that the initial hardening phenomena of the studied steel during C‐F exposure was mainly attributed to the dislocation strengthening and a certain level of carbides precipitation strengthening, while the subsequent softening behaviors were resulted from dynamic recovery and coarsening of carbides. Moreover, as compared to other coatings, the self‐healing coating is able to improve the mechanical properties of steels due to dislocation strengthening, precipitation strengthening, and the self‐healing behavior resulting from the reaction between the TiC layer and oxygen.

Effect of Adding Intermediate Layers on the Interface Bonding Performance of WC-Co Diamond-Coated Cemented Carbide Tool Materials.

The interface models of diamond-coated WC-Co cemented carbide (DCCC) were constructed without intermediate layers and with different interface terminals, such as intermediate layers of TiC, TiN, CrN, and SiC. The adhesion work of the interface model was calculated based on the first principle. The results show that the adhesion work of the interface was increased after adding four intermediate layers. Their effect on improving the interface adhesion performance of cemented carbide coated with diamond was ranked in descending order as follows: SiC > CrN > TiC > TiN. The charge density difference and the density of states were further analyzed. After adding the intermediate layer, the charge distribution at the interface junction was changed, and the electron cloud at the interface junction overlapped to form a more stable chemical bond. Additionally, after adding the intermediate layer, the density of states of the atoms at the interface increased in the energy overlapping area. The formant formed between the electronic orbitals enhances the bond strength. Thus, the interface bonding performance of DCCC was enhanced. Among them, the most obvious was the interatomic electron cloud overlapping at the diamond/SiCC-Si/WC-Co interface, its bond length was the shortest (1.62 Å), the energy region forming the resonance peak was the largest (-5-20 eV), and the bonding was the strongest. The interatomic bond length at the diamond/TiNTi/WC-Co interface was the longest (4.11 Å), the energy region forming the resonance peak was the smallest (-5-16 eV), and the bonding was the weakest. Comprehensively considering four kinds of intermediate layers, the best intermediate layer for improving the interface bonding performance of DCCC was SiC, and the worst was TiN.

Interfacial reaction behavior of titanium/steel composite plate formed by cold-hot rolling

Titanium/steel composite plate was prepared by cold-hot rolling method. The influence of temperature on the interfacial reaction behavior of titanium/steel composite plate was studied by double beam focused ion beam system and spherical aberration correction transmission electron microscopy. The results show that the interfacial reaction of the cold-rolled titanium/steel composite plate mainly occurs in the heating stage, and the continuous intermetallic compounds layer formed at the interface during heating fractures during hot rolling. An interfacial layer composed of submicron TiC layer and α-Ti/α-Fe is formed when the hot rolling temperature is not higher than 850 °C, and the interfacial bonding strength increases with the increase of rolling temperature. An interface layer composed of micro (FeTi+TiC)/Fe2Ti layer, nano FeTi/Fe2Ti layer and micro pores is formed when the hot rolling temperature exceeds 900 °C. The interfacial micro (FeTi+TiC)/Fe2Ti layer and micro pores will seriously damage the interfacial bonding quality.

Vacuum brazing of TZM alloy and graphite with Ti-35Ni alloy: Microstructure, properties, and mechanism

In the present work, a reliable TZM/graphite heterogeneous joint was prepared by vacuum brazing with Ti-35Ni alloy. The influence of brazing temperature on the interfacial microstructure, shear strength, and fracture characteristics of the joints were analyzed. The formation mechanism of the joints was also investigated in detail. TiC layer was formed on graphite during the vacuum brazing process, characterized by SEM and TEM analysis. The interfacial microstructure of the joints brazed at 1200 °C was TZM/Ti(s,s)/TiNi + Ti2Ni/TiC/graphite. The thickness of TiC layer gradually increased with the increase in brazing temperature. In addition, the shear strength of TZM/graphite heterogeneous joints increased first and then decreased, reaching the peak value of 14.5 MPa at 1300 °C. Under optimal vacuum brazing temperature, the fracture path of the joint started in the TiC layer and then extended to the interior of the graphite substrate.

Achieving high-temperature thermal evacuation between dissimilar materials Cf/C and Mo30Cu by forming a brazed joint

Achieving a high heat transfer is essential for the Cf/C-Mo30Cu dissimilar material components in their applications of thermal nuclear reactions. In this study, the Cf/C composite and the Mo30Cu alloy were successfully brazed by using the Ag-Cu-4.5Ti braze to eliminate interface gaps between them. The maximum thermal conductivity of the Cf/C-Mo30Cu joint at 860 °C /10 min reached 112 W·m−1·K−1(RT). The thermal conductivity of the joint even exceeds that of the Cf/C matrix (107 W·m−1·K−1). It is worth noting that the overall thermal conductivity of the joint can still reach 92 W·m−1·K−1 at 500 °C. Shear test results showed that the average shear strength of the joints achieved 13.1 MPa at the highest thermal conductivity of the joint. A homogeneous TiC layer is generated along the Cf/C interface, which is crucial for maintaining a stable joint and providing a favorable heat transfer channel across the Cf/C-Mo30Cu dissimilar materials.

Large‐scale fabrication of TiC@C powders and its effect on the properties of Al2O3‐MgO‐C castables

AbstractHigh performance carbon containing castables have always been pursued by researchers and steelmaking producers, unfortunately, poor water‐wettability of graphite flakes was greatly limited their application in castables. To respond this, we proposed a large‐scale and low‐cost modified molten salt shielding synthesis technique for fabricating TiC coated graphite in air atmosphere using graphite flake and Ti powder as raw materials. Microstructure, wettability and oxidation resistance of TiC@C powders, and effect of TiC@C powders on the properties of Al2O3‐MgO‐C castables were investigated. The results demonstrate that TiC coated graphite was synthesized via modified molten salt shielding synthesis route in air atmosphere. A uniform and continuous TiC layer was formed on the surface of graphite, thereby significantly improving the water‐wettability and oxidation resistance of graphite flakes. The castables with 5% TiC@C powders possessed lower apparent porosity, higher cold strength, good oxidation resistance, and slag resistance in comparison with the castables with graphite flakes, and slag resistance were also better than Al2O3‐MgO castables. The as‐fabricated TiC@C powders have good water‐wettability and oxidation resistance, making them as a prime carbon source for producing carbon containing castables for steel ladle linings.

Development of a functional hardness gradient in WC-TiC-Co cemented carbide during gradient sintering

In this study two functionally graded cemented carbide samples with gradients in both composition and grain size have been produced and studied. The two samples are manufactured by local addition of TiC to a pressed WC-Co green body prior to sintering. The two samples differ only by the in-going WC particle size, where one sub-micron and one coarse WC particle size is used. The Ti, Co, and C concentration profiles are analysed using energy−/ and wavelength-dispersive X-ray spectroscopy; Vickers hardness profiles are also measured. Furthermore, the measured experimental concentration profiles are compared with diffusion simulations using the DICTRA software. The concentration and hardness profiles show a similar trend for both samples with decreasing Ti and C concentrations while Co concentration increases with distance from the applied TiC layer. The composition gradient affects the number of stable phases and the WC grain size. Furthermore, there are distinct differences between the samples with different initial WC particle size. The sample with an initially finer WC particle size has a shorter gamma-phase zone and the difference in WC grain size across the gradient is larger as compared to the sample with an initially coarser WC particle size. Finally, abnormal grain growth occurs in both samples but it is suppressed with increasing Ti concentration.

Alternative approach for the growth of a TiB2/TiC multilayer on M2 steel using the duplex method: Cathodic arc physical vapor deposition and cathodic reduction and thermal diffusion boriding

An alternative approach for producing a hard TiB2/TiC multilayer on M2 high-speed steel was introduced by combining cathodic arc physical vapor deposition (CA-PVD) and cathodic reduction and thermal diffusion-based boriding (CRTD-Bor). In this regard, the CRTD-Bor process was applied on CA-PVD Ti-deposited M2 steel and the effects of boriding parameters (i.e., temperatures and durations) on multilayer growth were examined. During boriding, Ti coating on the substrate was converted into Ti-borides on the top surface and a TiC layer was simultaneously formed at the interface of the Ti deposit and the steel matrix. The growth of boride and carbide phases was found to obey the parabolic law. The pre-exponential factors (K0) and the activation energy (Q) values were calculated as 7.50 × 10−9 m2/s and 146.10 kJ/mol for TiB2 growth and 1.81 × 10−7 m2/s and 187.31 kJ/mol for TiC formations, respectively. Additionally, empirical equations for estimating the thicknesses of TiB2 and TiC layers were derived. The penetration depth-dependent hardness measurements revealed the TiB2 layer hardness as 41 ± 5 Gpa, which decreased gradually toward the TiB region (24 ± 2 GPa) and fell to 13 ± 1 GPa in the Ti-rich area. The hardness then increased to 20 ± 1 GPa with the contribution of the TiC layer adjacent to the substrate. This multilayer coating exhibited −5.5 to −4.5 GPa compressive stress and good adhesions (HF1) to the substrates. Also, the results of tribological tests indicated a sevenfold increase in wear resistance under dry sliding conditions.

Synergistic optimization of mechanical and tribological properties of TiC modified copper-graphite composites by direct current in-situ sintering

The application of Cu-graphite composites in the field of friction materials is limited by the poor wettability between Cu and graphite and weakened mechanical properties. In this work, in-situ TiC layers were generated by interfacial resistance sintering with direct current to manipulate the interfacial bonding of the composites and enhance their comprehensive properties. The Ti added to the composites would react with graphite at the interface to generate TiC layers and form strong Cu–TiC-graphite interfaces due to interfacial reactions. When the added Ti content is 6 wt%, the composite demonstrates the most excellent mechanical properties and tribological characteristics, i.e., yield strength (168 MPa) and wear rate (2.7 × 10−10 m2/N) are 93.1% higher and 29.7% lower than those of the Cu-graphite composite without Ti addition, respectively. The dense TiC layer induces the strengthening of the Cu matrix and serves as the reinforcing phase to optimize the interfacial bonding and stress transfer, which not only greatly enhances the mechanical properties of the composite but also enables the composite to take full advantage of the hard TiC and graphite phases to obtain stable friction coefficient and low wear rate. This work provides a simpler technique to prepare modified Cu-graphite composites with excellent performance and contributes to the in-depth understanding of the enhancement mechanism of hard ceramic layers on the mechanical and tribological properties of composites.

Structural and mechanical properties of Al/TiC interface with vacancies: First-principles study

The adhesion, stability, electronic structure, and ductility of Al/TiC interfaces with Al, Ti, and C vacancies (Alv, Cv and Tiv) are investigated using first-principles calculations. The results show that the adhesion can not be improved significantly by Alv. The adhesion of Al/TiC interfaces with Cv and Tiv are stronger than the clean interface. We find the Al atoms will replace the Tiv in the TiC layer for Ti-site with Tiv. Interestingly, the interface will shift from Ti-site into C-site for 75% Tiv. Furthermore, the results of the generalized stacking fault (GSF) energies show that the preferred slip direction is the 〈110〉 direction. Based on the Rice criterion of ductility, it is found that Cv will make the interface more brittle. But the ductility of the Al/TiC interface can be improved by Tiv. The theoretical adhesion of Al/TiC interfaces with Cv is in good agreement with experimental results.

The effect of the process gas mixture ratio on the structure and composition of TiC and TiCN thin layers prepared by cathodic arc deposition on tool steel

The presented research introduces the possibilities of setting the parameters of the deposition of thin coatings so that the desired surface properties are achieved. For the examined TiCN and TiC thin coatings, applied by the cathodic arc method (Arc-PVD), the dependence was revealed between the hardness of the coatings, the residual stress, and the wear resistance, which significantly affect the service life of the coated parts. The statistical analysis of the results shows the optimal ratio between nano-hardness and internal stress, at which the least wear of the layer occurs (the ratio of hardness and magnitude of compressive stress must be approximately equal to 10). The research is focused on predicting the utility properties of thin TiCN coatings to reduce the wear of modified surfaces.

Interfacial microstructure and mechanical properties of WC–Co/40Cr joints brazed at low–temperature with Ag–Cu–Ti + Sn novel filler

It is crucial to design a novel active filler metal for brazing WC–Co cemented carbide–steel joints at low temperatures. In this study, we designed a low-melting-point multi-component active filler metal (Ag–Cu–Sn–Ti) based on Ag–Cu–Ti filler metal to achieve perfect combination of WC–Co/40Cr steel joints. The interfacial microstructure of the WC–Co/40Cr steel joint was comprehensively characterized, and the joint-bonding mechanism, mechanical properties, and fracture behavior after brazing at 700–780 °C were systematically analyzed. On both sides of the filler metal, WC and α-Fe combined with the TiC layer, enhancing the bonding of the filler metal to base materials. The typical structure of the joint is WC–Co/TiC layer/Co2SnTi + Cu–doped Cu81Sn22 + Ag [s, s] + Ti–Cu granules/TiC layer/40Cr. The maximum shear strength of 241 MPa was obtained when the joint was brazed at 740 °C for 10 min, which is approximately 50% higher than those of previous low-temperature vacuum-brazed WC–Co/steel joints. The main factors leading to premature failure of joint include the distribution of phases in filler metal layer and defects of WC–Co caused by Co diffusion.

Structural modification of TA2/Q355B composite interface and study of TiC stability mechanism

Constructing different titanium/steel composite interface structures and stabilising the TiC layer at 950°C through structural modification, the coexistence of multiple brittle phases at the composite interface was reduced and discussed the formation mechanism. Through structure modulation, the organisation of the bonding interface near the Ti side transformed into α-Ti, and the bond strength significantly increased to 290 MPa. Break through the rolling temperature should be limited to below 850°C, and the rolling temperature increases to 950°C. The bonding interface is transformed from discontinuous TiC and aggregated Fe2Ti particles to a uniform and continuous TiC layer at 850 and 900°C. Achieving a regulated TiC layer thickness of 180–190 nm inhibited Fe2Ti and FeTi production.

Brazing of Ti-coated SiC using a CoFeCrNiCu high entropy alloy filler via electric field-assisted sintering

Electric field-assisted sintering technology (FAST) was used to join SiC ceramic by using a CoFeCrNiCu high-entropy alloy filler. A thin Ti film was deposited on SiC surface by physical vapor deposition to reduce the residual thermal stress in the joint. The microstructure, bending strength, and bonding mechanism were systematically investigated. It was found that a discontinuous TiC layer could be formed at the interface and the interfacial reaction products changed with different brazing temperatures. A joint with a bending strength of 72 MPa was achieved at 1200 °C, which is 73% higher than that of the SiC brazed without Ti coating. This work provides a new insight in the interfacial design of ceramic brazing with high mechanical properties.

In-situ synthesis of Si@G@TiC double protective layer structure for enhancing cycling stability of lithium-ion batteries

Si-based materials are considered as the highly promising candidates for the next-generation high performance Li-ion batteries, and the development of Si/graphite anode is regarded as one of the common approaches to realize commercial application of it. Unfortunately, although the introduced graphite phase improves the electrical conductivity, the poor interfacial bonding strength as well as the limited ability to relieve the volume expansion of silicon still lead to the inferior cycle performance. Herein, a novel Si-based anode structure is constructed and modified with a double protective layer, in which the inner graphite is in close contact with silicon to improve the electrical conductivity while partially alleviating the volume expansion of silicon, and the outer rigid TiC layer further stabilizes the electrode structure as well as suppress the side reactions between active materials and electrolyte. Owing to the unique structural design, the cycling performance of the Si@G@TiC electrode is greatly improved, and the capacity retention of the electrode is high up to 85% after 300 cycles at 0.2 A g−1.

Interfacial evolution of titanium/steel clad plates during pulsed tungsten inert gas welding

Joining titanium alloy with steel has important applications in the shipbuilding and aerospace industries. Successful titanium/steel joints fabricated by explosive welding have been reported recently. However, explosive welding is not ideal for welded structures with complex geometry. Here, pulsed tungsten inert gas (TIG) welding is introduced to promote the application of explosively welded transition joints. In this work, pulsed TIG of commercially pure titanium to mild steel with an explosively welded titanium/steel transition joint was carried out. The results showed that at peak current (Ip) ≤ 260 A, the TiC layer hampered the generation of FeTi and Fe2Ti. However, at Ip = 300 A, the TiC layer broke up, which resulted in the thickness of FeTi and Fe2Ti increasing sharply to 0.8 μm.

Gradient interface formation in Cu–Cr/diamond(Ti) composites prepared by gas pressure infiltration

Interface design is critical to enhance thermal properties of Cu/diamond composite as a promising thermal management material. Herein we combine Cr alloying in Cu matrix with Ti coating on diamond particles to prepare a Cu-0.5 wt%Cr/diamond(Ti) composite in an attempt to construct a TiC/Cr3C2 gradient interface to improve phonon transfer at the interface. The Ti-coating on diamond particles transforms to a TiC layer during deposition. As the TiC layer is 20 nm thick, a part of Cr atoms in the Cu matrix diffuse through the TiC layer to react with the C atoms on diamond particles to form a 30 nm-thick Cr3C2 layer, and a 28 nm-thick graphite layer is generated on diamond particle surface. With increasing the TiC layer thickness to 80 nm, a small part of Cr atoms can still pass through the TiC layer to form discrete chromium carbide particles and a 20 nm-thick graphite layer is generated. The interfacial structure of the Cu-0.5 wt%Cr/diamond(Ti) composite is characterized as diamond/graphite/TiC/Cr3C2/Cu, and the thermal conductivity for the Cu-0.5 wt%Cr/diamond(Ti) composite has a 549 W m−1 K−1 value lower than the 735 W m−1 K−1 value for the Cu/diamond(Ti) composite. The lowered thermal conductivity is attributed to the formed graphite layer and the thick Cr3C2 layer in the Cu–Cr/diamond(Ti) composite. This study provides guidance for designing and tailoring gradient interface for efficient phonon transport in Cu/diamond composites.