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1.
《Ceramics International》2022,48(9):11915-11923
In this study, monolithic AlCrSiN, VN, and nano-multilayered AlCrSiN/VN coatings were deposited using a hybrid deposition system combining arc ion plating and pulsed direct current magnetron sputtering. The microstructure, thermostability, mechanical, oxidation and tribological properties of the coatings were comparably investigated. The multilayered AlCrSiN/VN coating exhibited a face-centered cubic (fcc) structure with (200) preferred orientation and showed the highest hardness (30.7 ± 0.5 GPa) among these three coatings due to the multilayer interface enhancement mechanism and higher compressive stress. The AlCrSiN sublayers effectively prevented the V element from rapid outward diffusion to the surface of AlCrSiN/VN coating at elevated temperatures, which improved the oxidation resistance of the coating. Decomposition of V (Cr)–N bonds occurred at annealing temperatures from 800 °C to 1000 °C and V2N phase appeared at 1100 °C. The AlCrSiN/VN coating showed excellent tribological performance at high temperatures by combining the merits of VN layers for low friction coefficient and AlCrSiN layers for superior oxidation resistance. Compared to VN and AlCrSiN coatings, AlCrSiN/VN coating showed the lowest wear rate of 2.6×10-15 m3/N·m at 600 °C and lowest friction coefficient of 0.26 at 800 °C with a relativity low wear rate of 39.4×10-15 m3/N·m.  相似文献   

2.
This study focuses on examining the effect of PVD coatings on the oxidation performance of interconnects in fuel (anode) side environments. A Fe‐22Cr ferritic steel was coated with (i) Ce 10 nm (ii) La 10 nm and (iii) Co 600 nm. The samples were exposed at 850 °C in Ar‐5% H2‐3% H2O in a tubular furnace over 500 h. Additionally, the effect of a pre‐oxidation step was investigated by exposure in air prior to the simulated fuel gas environment. Chemical analysis on the samples was subsequently performed with SEM/EDX and XRD. It was established that the Ce and La coatings brought about a factor 2–3 reduction (kp values of 2.16 × 10−14 ± 3.6 × 10−15 g2 cm−4 s−1 for the La 10 nm coated steel compared to 7.72 × 10−14 ± 5.86 × 10−15 g2 cm−4 s−1 for the uncoated steel) in the oxidation rate while the Co coating disintegrated into metallic islands in and on the thermally grown oxide after exposure. Additionally, the La coating resulted in the formation of a continuous perovskite layer by reaction with the thermally grown oxide.  相似文献   

3.
Titanium diboride (TiB2) is considered as a promising cathode material for Al production. However, the manufacture of TiB2 cathodes is facing numerous challenges. In this study, electrodeposition of TiB2 on graphite was performed in molten fluoride (FLiNaK) electrolyte at 600°C by using a periodically interrupted current technique for various electrodeposition times (from 10 to 75 minutes) and at two different current densities (−0.12 and −0.5 A/cm2). It is shown that the TiB2 coating morphology/microstructure strongly depends on the applied current density. Denser coatings were obtained at jon = −0.12 A/cm2 with a growth rate of ca. 0.7 µm/min. The thicker films display a preferential crystallographic orientation along the [110] plan. At jon = −0.5 A/cm2, TiB2 coatings are deposited at a growth rate of ca. 6 µm/min with no crystallographic texture. They present a porous and stratified morphology with numerous transversal macrocracks. All TiB2 coatings show excellent wettability for molten Al as confirmed by sessile drop experiments. However, significant molten Al infiltration occurs in the TiB2 coatings, which accumulates at the coating/graphite interface, inducing the coating delamination.  相似文献   

4.
In this research, a SiC/ZrB2 coating was produced on graphite by reactive melt infiltration and plasma spraying method. The coating characterization was performed using XRD analysis, electron microscopy equipped with energy dispersive spectrometer (EDS), and supersonic flame ablation test at 2073 K. The results indicated that the dense C/SiC coating with good ablation resistance can be obtained at 1873 K. The coating thickness decreased with increasing infiltration temperature. The results of ablation test showed that by increasing the infiltration temperature and holding time, weight loss and mass ablation rate decreased from 22.63% to 9.83% and 3.63 × 10−3 g cm−2 s−1 to 1.34 × 10−3 g cm−2 s−1, respectively. The results showed that by using the ZrB2 as outer coating the ablation resistance improved remarkably. The weight loss and mass ablation rates for the SiC/ZrB2 coating were 12.79% and 1.857 × 10−3 g cm−2 s−1, respectively.  相似文献   

5.
Oxidation-resistant yttrium silicates coatings for SiC precoated carbon/carbon composites were prepared by a novel hydrothermal electrophoretic deposition process. Sonochemical-synthesized yttrium silicates nanocrystallites, isopropanol, and iodine were respectively used as source materials, solvent, and charging agent during the deposition. Phase compositions, surface and cross-section microstructures of the as-prepared multilayer coatings were characterized by an X-ray diffractometer (XRD) and a scanning electron microscopy (SEM). The influence of deposition temperatures on the phase, microstructure, and oxidation resistance of the multilayer coated C/C composites was particularly investigated. Results show that the as-prepared outer coatings are composed of yttrium silicates crystallites with a main phase of Y2Si2O7 and Y2SiO5. The thickness and density of the yttrium silicates coatings are improved with the increase of deposition temperature. Compared with SiC coating prepared by pack cementation, the multilayer coatings prepared by pack cementation with a later hydrothermal electrophoretic deposition process exhibit better antioxidation properties. The as-prepared multilayer coatings can effectively protect C/C composites from oxidation at 1773 K in air for 35 h with a weight loss of 0.32 × 10−3 g/cm2.  相似文献   

6.
Spent MoSi2 and MoB were used as raw materials to prepare multilayer MoSi2/MoB coating on molybdenum by the two-step method of slurry deposition and spark plasma sintering. The results showed dense MoSi2/MoB coating after sintering while penetrated cracks appeared in MoSi2 coating due to coefficient of thermal expansion mismatch between the Mo substrate and coating. After the sintering of MoSi2/MoB coatings, MoB and Mo2B diffusion layers were formed between MoB transition layer and Mo substrate without defects, exhibiting good metallurgical bonding. The high-temperature oxidation behavior of coatings (1500°C) was also explored. After oxidation of 50 h at 1500°C, lowest mass gain (0.035 mg/cm2) was obtained for MoSi2/MoB coating, and the oxide scale was dense and complete without voids, making the oxygen diffusion at elevated temperature inhibited. Compared with MoSi2 coating under the same oxidation conditions, relatively thinner silica oxide scale was acquired by MoSi2/MoB coating because of the reduction of cracks, and the multilayer coating exhibits better anti-oxidation properties at high temperature.  相似文献   

7.
An excellent anticorrosion Mg–Al layered double hydroxide (LDH) composite coating was successfully fabricated on LA43M magnesium alloy substrates via an in situ steam coating (SC) process and a subsequent hydrothermal treatment at different temperatures. The microstructure, composition and phase formation of the composite coatings were studied via X-ray diffractometer, energy disperse spectroscopy, and scanning electron microscope, respectively. The corrosion resistance of composite coatings was further investigated using electrochemical measurements and corrosion test. The results showed that LDH/SC composite coating has typical nanosheets microstructure, which effectively seal the defects of SC. As the hydrothermal temperature increases, the thickness and density of nanosheets increases, and the corrosion resistance was significantly improved. Especially, the Mg–Al LDH/SC composite coating prepared at 100°C was the most dense and thickness, and exhibited the optimal and long-term anticorrosion resistance in 3.5 wt.% NaCl soultion. It has the lowest Icorr (1.767 × 10−8 A/cm2), which decreased by three and two orders of magnitude compared with the bare substrate and SC. Furthermore, it can maintain good chemical stability after immersion in the corrosion medium for 192 h and its hydrogen evolution rate (0.00416 mL·cm−2·h−1) and weight lost rate (0.00266 mg·cm−2·h−1) were the lowest compared with other samples.  相似文献   

8.
Plasma spray coating with ceramic carbide is a promising approach for improving the surface quality of the materials. In this work, the effectiveness of tungsten carbide (WC), chromium carbide (Cr3C2), and the composite coating of the two powders in the weight ratio of 50:50 were investigated. In the erosion test, aluminum oxide (Al2O3) particles were combined with a high-speed air-jet and impinged at 90° on the top surface of the material. Electrochemical polarization and electrochemical impedance spectroscopy studies were conducted with a 3.5 wt.% of sodium chloride (NaCl) solution as the electrolyte. Using a scanning electron microscope, the surface morphology of powders and coatings, as well as the mechanisms of erosion and corrosion, were studied. Energy-dispersive X-ray analysis and X-ray diffractometry were used to reveal the composition and elemental distribution of the feedstock powders and coatings. Because of the presence of hard phases, the composite coating shows the highest average microhardness of 1350.2 HV. The composite coating exhibits improved erosive wear resistance with an increase in erodent exposure time. The Cr3C2 coating has a reduced corrosion current density of 1.404 × 10−5 mA/cm2 and a higher charge transfer resistance of 2086.75 Ω cm2 due to passivation.  相似文献   

9.
The mullite and ytterbium disilicate (β-Yb2Si2O7) powders as starting materials for the Yb2Si2O7/mullite/SiC tri-layer coating are synthesized by a sol–gel method. The effect of SiC whiskers on the anti-oxidation properties of Yb2Si2O7/mullite/SiC tri-layer coating for C/SiC composites in the air environment is deeply studied. Results show that the formation temperature and complete transition temperature of mullite were 800–1000 and 1300°C, respectively. Yb2SiO5, α-Yb2Si2O7, and β-Yb2Si2O7 were gradually formed between 800 and 1000°C, and Yb2SiO5 and α-Yb2Si2O7 were completely transformed into β-Yb2Si2O7 at a temperature above 1200°C. The weight loss of Yb2Si2O7/(SiCw–mullite)/SiC tri-layer coating coated specimens was 0.15 × 10−3 g cm−2 after 200 h oxidation at 1400°C, which is lower than that of Yb2Si2O7/mullite/SiC tri-layer coating (2.84 × 10−3 g cm−2). The SiC whiskers in mullite middle coating can not only alleviate the coefficient of thermal expansion difference between mullite middle coating and β-Yb2Si2O7 outer coating, but also improve the self-healing performance of the mullite middle coating owing to the self-healing aluminosilicate glass phase formed by the reaction between SiO2 (oxidation of SiC whiskers) and mullite particles.  相似文献   

10.
《Ceramics International》2021,47(21):30319-30330
Doping light elements into ceramic coatings on different metal substrates by anodic-spark electrolysis (ASE) to improve their properties, such as wear and corrosion resistance, has recently attracted a lot of attention. In this study, nitrogen-doped Al2O3 composite ceramic coatings had been fabricated in eco-friendly KOH–NaNO2 electrolytes using the anodic-spark electrolysis (ASE) method after 9 min at a fixed applied ASE voltage (75 V higher than the breakdown voltages). To deposit a nitrogen-doped coating with high amounts of oxynitride phases possible, we thoroughly studied the ASE coatings deposited in different total variable salts concentrations (KOH+NaNO2) and NaNO2/KOH ratios of ASE electrolytes. The coating properties were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FT-IR), and the electrochemical impedance spectroscopy (EIS) tests. The results indicated that the coating produced in the KOH–NaNO2 electrolyte with a low total variable salts concentration (2 gr.L−1) and a high NaNO2/KOH ratio value (3) is optimum in the investigated conditions. It has the highest percentage of nitrogen-doped phases, such as N-doped γ-Al2O3 and γ-AlON (γ-Al2.78O3.65N0.35), and a homogeneous morphology of surface with the smallest average size of pores (<14 μm2). This coating showed the significantly higher corrosion resistance with a 4.101104 × 106 Ω cm2 value compared to the uncoated aluminium substrate with a corrosion resistance value of 0.094195 × 106 Ω cm2 after 48 h of immersion in the 3.5 wt% NaCl solution. The approach presented herein provides an attractive way to modify the surface of aluminium alloys to improve corrosion behaviour.  相似文献   

11.
Yttria partially stabilized nanostructured zirconia coatings were deposited by atmospherical plasma spraying (APS). The microstructure of the as-sprayed nanostructured coating was characterized with Scanning electronic microscopy (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectrum (RS). The laser-flash diffusivity method and push-rod method were used to examine the thermomechanical properties of the nanostructured zirconia coatings. The results obtained indicated that the plasma-sprayed zirconia coating possessed nano-structure and its average grain size was about 73 nm. The average thermal expansion coefficients of the nanostructured coating at the first thermal cycle and second thermal cycle from room temperature to 1200 °C are 11.0 and 11.6×10−6 °C−1, respectively. The thermal diffusivity of the nanostructured zirconia coating was 1.80–2.54×10−3 cm2/s between 200 and 1200 °C. The microhardness of the nanostructured zirconia coating was 8.6 GPa, which was 1.6 times as large as that of traditional zirconia coating.  相似文献   

12.
《Ceramics International》2022,48(7):9550-9557
To improve the high-temperature oxidation resistance and electrical conductivity of ferritic stainless steels, protective Ce-doped NiMn2O4 spinel coatings were fabricated on the surface of SUS430 steel by electrophoretic deposition (EPD). The phase structure and microstructure of Ce-doped NiMn2O4 in both powder and coating forms were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The high-temperature oxidation of the NiMn2O4 spinel coating before and after Ce doping in the air at 800 °C for 168 h was studied by weight gain experiments. The area-specific resistance (ASR) of coatings was measured by a standard four-probe method. It was found that the Ce-doped NiMn2O4 spinel powder displayed a stable structure, high crystallinity, fine grain size, and decreased agglomeration when the Ce content was fixed at 0.05 mol?L?1. The oxidation kinetics of NiMn2O4-coated SUS430 steel before and after Ce doping obeyed a parabolic law with parabolic rate constants of 4.58 × 10?15 g2 cm?4 s?1 and 1.83 × 10?15 g2 cm?4 s?1, respectively. When oxidized at 800 °C for 50 h, the ASR value of the coated samples before and after Ce doping stabilized at about 15.2 mΩ?cm2 and 14.5 mΩ?cm2, respectively. This work demonstrated that the Ce-doped NiMn2O4 spinel coating improved the high-temperature oxidation resistance and the electrical conductivity of metal interconnects.  相似文献   

13.
Different ceramic coatings were prepared on the surface of 2024 aviation aluminum alloy using micro-arc oxidation process in silicate based electrolyte combined with the rare earth based compound Y(NO3)3·6H2O. The thickness, hardness of the coating and conductivity of electrolyte were tested using relative devices, morphology and chemical composition were studied by scanning electron microscope and energy dispersive spectroscope, respectively. The phase composition of the coatings was characterized by X-ray diffraction and X-ray photoelectron spectroscopy. Furthermore, the corrosion resistance of the coating was evaluated by an electrochemical workstation. The results showed that the addition of Y(NO3)3·6H2O could improve the thickness and hardness of the coating. The morphological observation of the coating showed that Y(NO3)3·6H2O was successfully incorporated into the ceramic layer and that the coating had the smallest porosity at 1.5 g/L Y(NO3)3. The phase composition of the coating was mainly γ-Al2O3, α-Al2O3, SiO2, Y2O3, and AlPO4. The corrosion resistance of coating in simulated seawater with the addition of Y(NO3)3·6H2O was significantly improved, and the values of |Z|0.01 Hz and corrosion rate of the coating reached the maximum and minimum at 1.5 g/L Y(NO3)3, which were 5.63 × 105 Ω cm2 and 7.444 × 10−4 mm/a, respectively.  相似文献   

14.
In the present study, a polymer-derived silicon oxycarbide (SiOC) ceramic layer has been coated on stainless steel 304 (SS304) to improve corrosion resistance in a seawater environment. The surface of SS304 is dip-coated with vinyl-functionalized polysiloxane, followed by pyrolysis under argon at 800°C to obtain SiOC layer with a thickness of about 1 μm after two-fold coating/pyrolysis steps. Structural characterization of the samples was performed by fourier transform infrared (FTIR), X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. Electrochemical characterization of SS304 and SiOC-coated SS304 is performed in 0.6 M NaCl solution. Potentiodynamic polarization measurements showed improved corrosion resistance of SiOC-coated SS304 with a very low corrosion current density of 4.14 × 10−9 A/cm2 whereas for uncoated SS304 corrosion current density of 4.56 × 10−7 A/cm2 was measured. Electrochemical impedance spectroscopic study confirmed superior corrosion resistance behavior of SiOC-coated SS304 over uncoated SS304.  相似文献   

15.
An AlCrN/nitrided layer (NL) composite coating was fabricated on H13 hot work mould steel using a cathode arc ion plating and low temperature plasma nitriding. The surface and cross-section morphologies, chemical composition, phases, and roughness of AlCrN/NL coating were analyzed using a scanning electron microscope (SEM), energy dispersive spectrometer, X–ray diffractometer (XRD), and atomic force microscope, respectively, the friction–wear performances of AlCrN/NL coatings at 400, 500, and 600°C were investigated using a high-temperature wear test. The results show that the AlCrN/NL coating with the surface roughness of 76.8 nm forms the AlN phase, which increase its hardness from 1088 HV of NL to 2381 HV. The average coefficients of friction (COFs) of AlCrN/NL coating at 400, 500, and 600°C are 0.70, 0.55, and 0.56, respectively, and the corresponding wear rates are 1.59 × 10−5, 9.77 × 10−5, and 3.93 × 10−5 mm3/N/m, respectively, as a result, the lowest average COF and wear rate are at 500 and 400°C respectively. The wear mechanism of AlCrN/NL coating at 400°C is primary abrasive wear, accompanied by adhesive wear, while those at 500 and 600°C are primary adhesive wear, accompanied by abrasive wear.  相似文献   

16.
《Ceramics International》2017,43(18):16512-16517
In order to improve the thermal shock resistance of the coated carbon/carbon (C/C) composites, a mullite whisker toughened mullite coating was fabricated on the surface of SiC pre-coated C/C composites (SiC-C/C) by molten-salt method with a later hot dipping process. The phase compositions, surface and cross-section microstructures, high temperature thermal shock resistance of the as-prepared multi-layer coatings were investigated. Results show that the introduction of mullite whiskers can effectively improve the density of the mullite outer coating and decrease the cracking of the coating during the thermal shock cycle process. After 100 times thermal shock cycles between 1773 K and room temperature, only 1.87 × 10−3 g cm−2 weight loss has been detected, indicating the achievement of the excellent thermal shock resistance.  相似文献   

17.
Thermal conductivity is a crucial parameter for evaluating the quality and thermal effects of ceramic coatings, especially for thermal barrier coatings. However, measurement by conventional method involves two problems: (a) it is difficult to peel off a ceramic coating from a substrate; (b) even if the coating can be peeled off, it is still hardly used as standard specimen in test. Therefore, the relative method was proposed to evaluate the thermal conductivity of ceramic coating. An analytical relationship among the thermal conductivities of the coating, the substrate, and the coating/substrate composite was established. Experiments on TA4 coated with YSZ coatings were carried out to demonstrate the feasibility of this novel method and to investigate the impact of temperature on the thermal conductivity of YSZ coatings. The experimental results demonstrated the validity and convenience of the relative method. With the increasing testing temperature, the thermal conductivity value of YSZ coatings displayed nonlinearity feature, that is, decreased from 1.4 to 1.3 (W m−1 K−1) in the temperature range of 32-300°C and then increased up to 1.58 W m−1 K−1 at 1000°C.  相似文献   

18.
A ternary-phase SiC/ZrB2-MoSi2-SiC multilayer coating was prepared on graphite by two-step reactive melt infiltration (RMI) method. The formation mechanism of the coating was studied by HSC chemistry software 6.0. The erosion resistance of the coating was investigated by supersonic flame erosion test at 90° angle, temperature of 2173 K and speed of 1400 m/s (Mach 4) for 120 s. Erosion test results revealed that the SiC/ZrB2-MoSi2-SiC multilayer coating had very good erosion resistance. Weight change percentage, mass erosion rate and linear erosion rate of the coating were −0.18 %, −0.027 × 10−3g cm−2 s−1 and 0.33 μm s−1, respectively. Microstructural characterization demonstrated that interesting structures such as rod-like, flake-like, spherical, worm-like and fibrous structures were formed during erosion test. The erosion mechanism of ZrB2-MoSi2-SiC coatings is controlled both chemically and mechanically. The reduction of chemical degradation can be attributed to the presence of MoSi2 particles and the reduction of mechanical degradation can be related to the presence of ZrB2 particles.  相似文献   

19.
A series of sodium iron titanate (NFTO)–fluorocarbon composite coatings have been prepared with the liquid-phase blending method. The effects of two types of NFTO, NFTO platelets, and NFTO whiskers, on the tribological and corrosion behaviors of the composite coatings, are systematically studied. The results show that the addition of NFTO can significantly enhance the friction-reducing and wear resistance performances of the fluorocarbon coating. Under dry sliding, the minimum specific wear rate is 1.67 × 10−4 mm3/Nm for the platelet-filled composite coatings and 1.15 × 10−4 mm3/Nm for the whisker-filled composite coatings, respectively, showing a decrease of 83.5 and 88.6% than that of pure coating. Under a simulated seawater environment, the minimum specific wear rate is 5.44 × 10−5 mm3/Nm for the platelet-filled composite coatings and 0.84 × 10−5 mm3/Nm for the whisker-filled composite coatings, respectively, showing a decrease of 90.5 and 98.5% than that of pure coating. The morphologies of worn surfaces, wear debris, and transfer films are analyzed, and the corresponding wear resistance mechanisms are discussed. The electrochemical impedance spectroscopy certifies a remarkably improved corrosion resistance of the composite coatings which have been immersed in 3.5 wt % NaCl solution for 30 days. The composite coating reinforced with 7.5 wt % platelets shows the highest resistance of 256.3 × 106 Ω·cm2, approximately two orders of magnitude higher than that of pure coating. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48936.  相似文献   

20.
《Ceramics International》2022,48(22):32973-32985
Multilayer structure design is one of the most promising methods for improving the comprehensive performance of AlCrN-based hard coatings applied to cutting tools. In this study, four types of AlCrSiN/AlCrVN/AlCrNbN multilayer coatings, with different modulated thicknesses, were deposited to investigate their microstructure, mechanical, tribological, and oxidizing properties. All multilayer coatings exhibited grain growth along the crystallographic plane of (200) with a NaCl-type face-centered cubic (FCC) structure. The results show that, as the modulation thickness decreases from ~35 nm to ~10 nm, (1) the grain refinement effect is increasingly evident; (2) all multilayer coatings show a hardness of >30 GPa and an elastic modulus of >300 GPa. Both the ability to resist elastic strain to failure and the plastic deformation of multilayer coatings increase. In addition, their resistance to cracking reduces; (3) the wear rates of these multilayer coatings reduce successively from 1.78 × 10?16 m3 N?1 m?1 to 7.7 × 10?17 m3 N?1 m?1. This is attributed to an increase in self-lubricating VOx and a decrease in adhesives from the counterparts; (4) the best high-temperature oxidation resistance was obtained for the multilayer coating with a modulated thickness of ~15 nm.  相似文献   

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