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1.
Ti3AlC2, one of Ti-Al-C MAX phases, has received extensive attention due to its unique nano-laminated structure and combined properties of metals and ceramics. However, ultra-high synthesis temperature exceeding 800 °C is a critical challenge for broad application of Ti3AlC2 coatings on temperature-sensitive substrates. In this study, Ti-Al-C coatings were deposited on Ti-6Al-4V substrates using high-power impulse magnetron sputtering (HiPIMS) and DC sputtering (DCMS) for comparison. Different from as-deposited amorphous Ti-Al-C coating by DCMS, nanocrystalline TiAlx compound was achieved by HiPIMS deposition due to highly ionized plasma flux with high kinetic energy. Furthermore, HiPIMS promoted the generation of dense and smooth Ti3AlC2 phase coating after low-temperature annealing at 700 °C, while annealed DCMS coating only obtained Ti2AlC. In-situ XRD demonstrated such Ti3AlC2 phase could be early involved in crystallization at 450 °C, lowest than synthesis temperature ever reported. The mechanical properties of Ti3AlC2 coating were also discussed in terms of structural evolution.  相似文献   

2.
《Ceramics International》2018,44(18):22520-22528
In this work, TiC/Ti3AlC2–Co cermet coatings with varying amounts of Ti3AlC2 were deposited by atmospheric plasma spraying (APS) process and their wear-resistant properties were discussed. The friction coefficients and wear rates at high-temperatures were measured through a ball-on-disk type friction test at 600 °C. In addition, the corresponding wear mechanisms were elucidated through the observation of phase changes and surface microstructural evolution of the coatings. The results indicated that the as-prepared coatings consisted of TiC, Ti, TiO2, Al2O3, Co and CoO phases, which were produced by the decomposition and oxidation of TiC and Ti3AlC2. Compared with other samples, the sample with 30 wt% Ti3AlC2 addition displayed the smallest friction coefficient and least wear rate. Its wear rate was about 1.26 times lower than that of reported TiC–Co cermet material and about 10 times lower than that of the typically used TiC–Ni cermet material, suggesting outstanding wear resistance at elevated temperature. The addition of Ti3AlC2 reduced the friction coefficient of the coating by producing more TiC and Al2O3 hard phases and a consequent reduction of coating porosity. When the amount of Ti3AlC2 in the coating was less than 30 wt%, the main wear mechanism was abrasive wear. As the content of Ti3AlC2 was increased in the coating, the wear mechanism changed from abrasive wear to adhesive wear and the wear pattern of the coating gradually transformed from the furrows to the debris. This transformation of mechanism was related to the synergistic effect of hardness and porosity of the coating, which resulted from the remaining content and the special layered structure of Ti3AlC2.  相似文献   

3.
《Ceramics International》2020,46(9):13711-13723
Multi-track Ti-based wear-resistant composite coatings were fabricated on TC4 alloy surfaces using laser-clad TC4 + Ni45 + Co–WC mixed powders with different Y2O3 contents (0, 1, and 3 wt%). The microstructure, microhardness, and tribological properties of the coatings were characterised using X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry, electron probe X-ray micro analyser, microhardness tester, and friction and wear testing apparatus. The results showed that the number of cracks on the coating surfaces gradually decreased with the addition of Y2O3 and that residual Co–WC powders existed in the coating subsurfaces. The phase composition of the coatings with different Y2O3 contents remained unchanged and was mainly composed of reinforcing phases of TiC, TiB2, Ti2Ni, and matrix α-Ti. With the addition of Y2O3, the coating microstructure was remarkably refined, the direction characteristic of the TiC dendrites obviously weakened, and the nucleation rate significantly increased. When the added Y2O3 was 3 wt%, a large amount of TiB2–TiC-dependent growth composite phases precipitated in the coating. The two-dimensional lattice misfit between (0001)TiB2 and (111)TiC was 0.912%, which indicated that TiB2 and TiC formed a coherent interface. When the amount of Y2O3 was increased, the microhardness of the coatings gradually decreased, and the wear volume of the coatings first increased and then decreased. Under the effect of the TiB2–TiC composite phases, the wear resistance of the 3 wt% Y2O3 coating was optimal. The 3 wt% Y2O3 coating friction coefficient was the lowest, and the wear mechanism was abrasive wear.  相似文献   

4.
Ti3AlC2 MAX phases have attracted increasing attention due to their unique properties. However, high synthesis temperatures of Ti3AlC2 bulk materials limit their further development. In this work, Ti3AlC2 coatings were prepared by a two-step method with filtered cathode vacuum arc (FCVA) deposition at room temperature and annealing at 800 °C for 1 h. The structure and properties of coatings were investigated. The results showed that the formation of Ti3AlC2 phase in the annealed coating depended on the C2H2 flow rate during deposition. At low C2H2 flow rates (≤ 9 sccm), almost no Ti3AlC2 phase was formed. As the C2H2 flow rate increased, the annealed coatings mainly exhibited Ti3AlC2 phases, the texture of which transformed from (104) to (105) planes. Meantime, the hardness of Ti3AlC2 coatings continuously increased to a maximum of 20.7 GPa, and the corrosion resistance first increased and then decreased with the increase of C2H2 flow rate.  相似文献   

5.
Composite coatings consisting of flake graphite and SiO2 fillers in a hyperbranched polycarbosilane (HBPCS) matrix were designed and prepared to meet the requirements of laser protection. The laser ablation behavior of the composite coatings were investigated. Control experiments were designed to study the performance of SiO2 during laser irradiation. The results show that the introduction of SiO2 changes the anti-laser protective mechanism and can improve the anti-laser property of the coating. High power laser irradiation results in pyrolysis of HBPCS and the formation of SiC particles. Chemical reactions between SiO2, graphite, and SiC play an important role in consuming energy, and provide an excellent cooling effect to the substrate, leading to decreased temperature. SiC particles formed on the surface of the laser ablation area act as a shield to prevent the laser from irradiating deeper layers of the coating. Due to the cooling effect and thermal stability of SiC, the proposed coating shows a good anti-laser property.  相似文献   

6.
《Ceramics International》2022,48(18):25788-25797
The Si-SiC-MoSi2 and Si-SiC coatings were proposed to repair the damaged MoSi2-SiC/SiC coated C/C composites by laser directed energy deposition. Laser ablation was used to assess the repair effect. Results showed that both the repaired coatings with dense structure could restore the geometric size of damaged area. Compared with the Si-SiC-MoSi2 coating, the Si-SiC repaired coating with higher laser reflectivity and more free Si could reduce the heat generation and enhance the heat dissipation during ablation, which lowered the maximum temperature by 347.49 K and 810.77 K under 300 W and 500 W ablation for 7 s separately, beneficial to avoid the secondary laser damage of the repaired area.  相似文献   

7.
《Ceramics International》2019,45(10):13119-13126
The low fracture toughness of ceramic coatings has always hindered their wide application. In this study, an in-situ nanocomposite coating was prepared by the atmospheric plasma spraying of a 50 wt% Ti3AlC2-50 wt% Cu mixed powder. The in-situ nanocomposite coating was found to have an unusual microstructure with a nano-micrometre phase synergistic enhancement, which consisted of submicrometre-thick layers of Cu and nanoparticles of Cu(Al), Ti4O5, TiO2, and Al2TiO5. Thus, in the spraying process, Al was delinked out of Ti3AlC2, forming a large amount of plastic Cu(Al) with Cu. The delinked channel provided a path for Cu to diffuse into Ti3AlC2, which a spatial Cu network structure was formed in the coating. The in-situ nanocomposite coating has high fracture toughness and crack growth resistance by a three-point bending test. This paper reports a new method to prepare a high-fracture-toughness composite ceramic coating.  相似文献   

8.
《Ceramics International》2023,49(2):1700-1709
Carbon fiber-reinforced silicon carbide (C/SiC) composites are important candidates for laser protection materials. In this study, ablation mechanism of C/SiC coated with ZrO2/Mo and ZrB2–SiC/ZrO2/Mo under laser irradiation was studied. ZrB2–SiC multiphase ceramic and ZrO2 ceramic were successfully coated on C/SiC composite by atmospheric plasma spraying technology with Mo as transition layer. Phase evolution and morphology of composite were investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Moreover, ablation behavior of the composite was investigated by laser confocal microscopy. Results showed that ablation mechanism of C/SiC composite was controlled by phase transformation, thermal reaction, and thermal diffusion, with solid–liquid transition of ZrB2 and ZrO2 being dominant factor. Endothermic reaction and good thermal diffusivity of coatings were also important factors affecting ablation performance. Reflectivity effect of ZrO2 coating was limited under high-energy laser irradiation. Compared with ZrO2/Mo single-phase-monolayer coating, designed ZrB2–SiC/ZrO2/Mo coating showed better ablation performance, and breakdown time of C/SiC increased from 10 to 40 s. The depletion of liquid phase in molten pool was identified as an important factor responsible for rapid failure of C/SiC. The coating failed when the entire liquid phase was consumed within molten pool, followed by rapid damage of C/SiC substrate. Results of this study can provide theoretical guidance and research ideas for design and application of laser protective materials.  相似文献   

9.
《Ceramics International》2022,48(2):1745-1756
In this study, Ti3AlC2 particles doped aluminum matrix composites were prepared by ultrasonic agitation casting method. Microstructure, mechanical properties, and tribological properties of pure aluminum and Ti3AlC2p/Al composites were characterized. Influence of different loads (10, 20, 30, and 40 N) and Ti3AlC2 contents (1.0, 2.0, 3.0, and 4.0 wt%) on the tribological behaviors of the composites were studied. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Energy dispersion spectroscopy (EDS), and 3D laser confocal were used to assist the analysis. The results indicated that fine and uniformly microstructure and the optimum comprehensive mechanical properties were exhibited on 2.0 wt%-Ti3AlC2p/Al composites. The abrasive grooves were widened and deepened with an increase in the load. The abrasion performance of composites improved distinctly with the addition of the Ti3AlC2 particles, which changed the wear mechanism from adhesive wear to abrasive wear. The 30 N load and the composites of 2.0 wt% Ti3AlC2 revealed the optimum tribological properties. The improvement of the tribological behavior of composites was attributed to the refinement of microstructure, the improvement mechanical properties and the three dimensional layered Ti3AlC2 phases with self-lubricating properties.  相似文献   

10.
《Ceramics International》2023,49(7):10525-10534
Thermal barrier coatings are an effective technology for improving the high-temperature performance of hot section components in gas turbine engine. Due to their excellent properties, high-entropy oxides are considered to be promising materials for thermal barrier coatings. Laser cladding is a coating preparation technology and the top coat prepared by laser cladding technology has an important application value for thermal barrier coatings. In this work, to improve the thermal cycling behavior of the La2(Ti0.2Zr0.2Sn0.2Ce0.2Hf0.2)2O7 high-entropy oxide coating, a bi-layer coating with the La2(Ti0.2Zr0.2Sn0.2Ce0.2Hf0.2)2O7 high-entropy oxide layer and the YSZ layer was designed and fabricated by laser cladding on the NiCoCrAlY alloy surface. The microstructure, phase and mechanical properties of the coating were analyzed by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and micro-hardness and nanoindentation tests, respectively. The results show that a bi-layer La2(Ti0.2Zr0.2Sn0.2Ce0.2Hf0.2)2O7/YSZ coating was successfully prepared by the laser cladding method, and shows good bonding at the interface between the layers. The high-entropy oxide layer maintains a relatively stable defective fluorite structure and its microstructure exists in the stable cellular and dendrite crystalline state after laser cladding. The high-entropy oxide layer prepared by laser cladding showed an average elastic modulus of 167 GPa and an average hardness of 1022.8HV in nanoindentation tests. Thermal cycling of the coating was carried out at 1050 °C. Failure of the bi-layer coating occurred after 60 thermal cycles at 1050 °C. Thermal stresses between different layers are calculated during thermal cycling. Due to its excellent mechanical properties, the bi-layer coating with the La2(Ti0.2Zr0.2Sn0.2Ce0.2Hf0.2)2O7 high-entropy oxide and YSZ layers is expected to become an effective high-entropy oxide thermal barrier coating.  相似文献   

11.
Features of the structural-phase reconstruction of the surface remelted layer (track) of ceramic specimens with different contents of Y2Ti2O7, Y3Al5O12, and Al2O3 under the action of directional laser heating have been investigated by the XRD, ATR-FTIR, EDS, and AFM methods. It has been established that, depending of the treatment mode (the irradiation power and traverse speed of the laser beam), the phase composition of the remelted layer changes as compared to that of the volume part of the ceramic specimen, and, as a result of the dissociation of predominantly Y3Al5O12 and Y2Ti2O7, cavities and asperities appear. High-temperature laser heating and the presence of a temperature gradient in tracks leads to an intensive ablation process from the surface of the tracks, as a result of which the surface layer of the tracks is depleted of the lower-melting components with a (Y2Ti2O7) and is enriched in more refractory components (Al2O3). A part of the ablation products is deposited in the form of oxides on the surface of tracks.The obtained results make it possible to represent a multilayer model of ceramics subjected to laser treatment: the ceramic volume proper with a specific phase composition → remelted volume layer with a changed phase composition → surface layer with a new changed phase composition, and deposited ablation products. The thickness of the layers depends on the irradiation mode, and clear-cut boundaries between them are absent.  相似文献   

12.
《Ceramics International》2023,49(4):6409-6418
Ni-based composite coatings reinforced by TiBX/TiXNiY/TiC with different Ti6Al4V contents were precipitated on a 35CrMoV substrate via laser cladding. The phase composition, elemental distribution, and precipitated phases of the coatings were characterised using X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy, and transmission electron microscopy. The mechanical and tribological properties of the cladding layer were also characterised. The results showed that the coating contained TiB2, TiC, TiB, Ni3Ti, and NiTi2 phases with uniform elemental distribution and grain refinement. A schematic of the growth model and precipitation sequence of the reinforced phases was generated. The microstructure, elemental segregation, hardness, and friction behaviour of the cladding layer were significantly influenced by the addition of Ti6Al4V. The optimal microstructure and best mechanical properties were obtained by the addition of 4 wt% Ti6Al4V, with that coating possessing a hardness, average friction coefficient, and wear volume of 770.8 HV1, 0.180 and 6132 um3, respectively.  相似文献   

13.
Ti3AlC2, as a toughening phase, was introduced into mullite ceramics for the first time by the pressureless sintering process aiming at improving the mechanical properties. Significant enhancement in density and mechanical performance of mullite ceramics was achieved through the introduction of Ti3AlC2 particles. The density of as-prepared mullite–Ti3AlC2 composites was increased by 23% (from 2.86 g/cm3 to 3.51 g/cm3) with Ti3AlC2 increasing from 0 wt% to 20 wt%. The formation of the liquid phase and decomposed particles from Ti3AlC2 are supposed to be responsible for the densification of mullite–Ti3AlC2 composites. The optimal mechanical properties were obtained in the mullite–Ti3AlC2 composites with 15 wt% Ti3AlC2. The bending strength, fracture toughness as well as Vickers hardness were reached 214.36 MPa, 4.84 MPa·m1/2, and 9.21 GPa, which are 40%, 74%, and 113% higher than pure mullite ceramics, respectively. The improved mechanical performance was mainly attributed to the synergetic action of crack deflection, crack branching and bridging, and strengthened grain boundary.  相似文献   

14.
A Y2Ti2O7/Al2O3 multilayer, exhibiting high thermal reflectivity and oxidation resistivity, holds potential as a functional surface coating for advanced gas turbine blades. Slight Al doping of Y2Ti2Ohas been found to significantly improve the structural stability of the multilayer, the detailed mechanism of which remains unclear. Hence, we examined the site occupancies of doped Al using high-angular resolution electron channeling X-ray spectroscopy with two-dimensional rocking of the incident electron beam. A statistical linear regression analysis of a set of observed ionization channeling patterns (ICPs) of fluorescent X-rays quantitatively confirmed that Al3+ preferentially occupied the Ti4+ site, rather than the Y3+ site, because of the large difference in the ionic radii of Al3+ and Y3+. Furthermore, the comparison of theoretical and experimental X-ray ICPs showed that oxygen vacancies VO were introduced at the 48f site, the first-nearest neighbor of the Ti site, which was consistent with the hypothesis that oxygen vacancies compensate for the local charge imbalance associated with preferential substitution of Al3+ for Ti4+. Our findings can aid in improving the thermal properties of environmental barrier coatings applied to advanced jet engines and also demonstrate the utility of beam-rocking schemes for investigating dopant effects in various functional materials.  相似文献   

15.
Using spark plasma sintering, Ti3AlC2/W composites were prepared at 1300°C. They contained “core‐shell” microstructures in which a TixW1?x “shell” surrounded a W “core”, in a Ti3AlC2 matrix. The composite hardness increased with W addition, and the hardening effect is likely achieved by the TixW1?x interfacial layer providing strong bonding between Ti3AlC2 and W, and by the presence of hard W. Microstructural development during high‐temperature oxidation of Ti3AlC2/W composites involves α‐Al2O3 and rutile (TiO2) formation ≥1000°C and Al2TiO5 formation at ~1400°C while tungsten oxides appear to have volatilized above 800°C. Likely due to exaggerated, secondary grain growth of TiO2‐doped alumina and the effect of W addition, fine (<1 μm) Al2O3 grains formed dense, anisomorphic laths on Ti3AlC2/5 wt%W surfaces ≥1200°C and coarsened to large (>5 μm), dense, TiO2‐doped Al2O3 clusters on Ti3AlC2/10 wt%W surfaces ≥1400°C. W potentially affects the oxidation behavior of Ti3AlC2/W composites beneficially by causing formation of TixW1?x thus altering the defect structure of Ti3AlC2, resulting in Al having a higher activity and by changing the scale morphology by forming dense Al2O3 laths in a thinner oxide coating, and detrimentally through release of volatile tungsten oxides generating cavities in the oxide scale. For Ti3AlC2/5 wt%W oxidation, the former beneficial effects appear to dominate over the latter detrimental effect.  相似文献   

16.
《Ceramics International》2020,46(10):16298-16309
The mass production of MAX phase coatings such as Ti3SiC2 and Ti3AlC2 using the plasma spraying method is highly challenging due to its ultra-high temperature and short reaction time. In this study, agglomerate powders of 3Ti/SiC/C/xAl with various Al contents (x = 0–1.5) were prepared to form TiC/Ti5Si3/Ti3SiC2 composite coatings using the plasma spraying technique. The effect of the Al addition on the microstructures and mechanical performances of the as-sprayed coatings was investigated. The addition of Al decreased the TiC content of the coatings while increasing their Ti3SiC2 content significantly. The addition of even small amounts of Al improved the MAX phase fraction of the coatings from 8.95 wt% (x = 0) to 34.05 wt% (x = 0.2) and 41.60 wt% (x = 0.5). Excess Al did not affect the Ti3SiC2 content of the coatings. The composite coatings showed a lamellar structure with pores and microcracks. With the addition of Al, the microhardness of the coatings increased slightly, while the fracture toughness improved significantly. The composite coatings with Al showed better wear resistance than those without Al. The wear mechanism of the coatings was a combination of adhesive wear, abrasive wear, and oxidative wear.  相似文献   

17.
A TiB2–Ti3AlC2 ceramic was manufactured by spark plasma sintering at 1900 °C temperature for 7 min soaking time under 30 MPa biaxial pressure. The role of Ti3AlC2 additive on the microstructure development, densification behavior, phase evolution, and hardness of the ceramic composite were studied. The phase characterization and microstructural investigations unveiled that the Ti3AlC2 MAX phase decomposes at the initial stages of the sintering. The in-situ formed phases, induced by the decomposition of Ti3AlC2 additive, were identified and scrutinized by XRD and FESEM/EDS techniques as well as thermodynamics principles. The sintered TiB2–Ti3AlC2 ceramic approached a near full density of ~99% and a hardness of ~28 GPa. The densification mechanism and sintering phenomena were discussed and graphically illustrated.  相似文献   

18.
《Ceramics International》2022,48(1):190-198
Ti3AlC2 ceramic exhibits potential in Ag-based composite electrical contact materials, but its interface characteristic with Ag matrix remains unexplored. In this work, sessile drop experiment is carried out to investigate the high-temperature wetting behavior of molten Ag with Ti3AlC2. Stable Ti3AlC2 is hardly wetted by molten Ag below 1000 °C(contact angle of 148.5°), but the wettability of Ag/Ti3AlC2 improves with the increasing temperature(final 14° at ~1130 °C). In contrast, the Ti3C2, a MXene with Al layer removed from its parent Ti3AlC2, exhibits inferior wettability with Ag(final 56.5° at ~1130 °C). Wetting mechanism of Ag/Ti3AlC2 is proposed on the basis of the interfacial structure and chemical composition. Increasing temperature accelerates dissociation of Ti3AlC2, and outward-escaping Al reacts with Ag to form interface layer with a composition of Ag4.86Ti8.66AlC7.59, Ag also diffuses along Ti3AlC2 grain boundaries and forms gradient reactive products(Ag–Ti–Al–C), which promotes their wettability. Finally comprehensive properties of Ag/Ti3AlC2 and Ag/Ti3C2 are compared. Al–Ag interdiffusion slightly decreases the electrical conductivity of Ag/Ti3AlC2 bulk material, but strengthen the interface bonding of composite and promote the viscosity of the molten pool, leading to the superior mechanical and anti-arc erosion properties. Absence of Al–Ag interdiffusion does remarkably improve the electrical conductivity of Ag/Ti3C2 bulk materials, but lack of Al layer damages the mechanical core and wettability with Ag, resulting in a drastic decrease of anti-arco erosion property.  相似文献   

19.
The phase transitions and He bubble evolution in Ti3AlC2 with the sequential He ions implantation and Fe ions irradiation at room temperature were investigated with grazing incidence X-ray diffraction and transmission electron microscopy. The pre-implanted He makes an obviously effect of suppressing the phase transitions caused by the following Fe ions irradiation. The following Fe ions irradiation was also found to create a competitive effect on the evolution of the pre-formed He bubbles. It can cause not only the growth of He bubbles, but the shrinkage (or re-solution of He bubbles). This will improve the resistance to He bubbles induced damage for Ti3AlC2. Both He ions implantation and Fe ions irradiation actually inhibit each other's irradiation damage to the material. This may play a positive role in reducing irradiation damage to the Ti3AlC2 material, and also provides new insight into irradiation resistance of this material.  相似文献   

20.
Thermal shock resistance is one of the performance-defining properties for applications where extreme temperature gradients are required. The thermal shock resistance of a material can be described by means of the thermal shock parameter RT. Here, the thermo-mechanical properties required for the calculation of RT are quantum-mechanically predicted, experimentally determined, and compared for Ti3AlC2 and Cr2AlC MAX phases. The coatings are synthesized utilizing direct current magnetron sputtering without additional heating, followed by vacuum annealing. It is shown that the RT of both Ti3AlC2 and Cr2AlC obtained via simulations are in good agreement with the experimentally obtained ones. Comparing the MAX phase coatings, both experiments and simulations indicate superior thermal shock behavior of Ti3AlC2 compared to Cr2AlC, attributed primarily to the larger linear coefficient of thermal expansion of Cr2AlC. The results presented herein underline the potential of ab initio calculations for predicting the thermal shock behavior of ionically-covalently bonded materials.  相似文献   

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