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1.
《Ceramics International》2017,43(15):12126-12137
Mechanical resistance of Al2O3 + TiO2 nanocomposite ceramic coating deposited by electrostatic spray deposition method onto X10CrAlSi18 steel to thermal and slurry tests was investigated. The coating was produced from colloidal suspension of TiO2 nanoparticles dispersed in 3 wt% solution of Al2(NO3)3, as Al2O3 precursor, in ethanol. TiO2 nanoparticles of two sizes, 15 nm and 32 nm, were used in the experiments. After deposition, coatings were annealed at various temperatures, 300, 1000 and 1200 °C, and next exposed to cyclic thermal and slurry tests. Regardless of annealing temperature and the size of TiO2 nanoparticles, the outer layer of all coatings was porous. The first five thermal cycles caused a rapid increase of aluminum content of the surface layer to 30–37 wt%, but further increase in the number of thermal cycles did not affect the aluminum content. The oxidation rate of coating-substrate system was lower during the thermal tests than during annealing. The oxidation rate was also lower for smaller TiO2 particles (15 nm) forming the coating than for the larger ones (32 nm). The protective properties of Al2O3 + TiO2 coating against intense oxidation of substrate were lost at 1200 °C. Slurry tests showed that coatings annealed at 1000 °C had the best slurry resistance, but thermal tests had weakened this slurry resistance, mainly due to decreasing adhesion of the coating.  相似文献   

2.
《Ceramics International》2023,49(19):31802-31814
Hexagonal boron nitride (hBN) with excellent self-lubrication performance is expected to relieve the friction resistance and wear of NiCr–Cr3C2 coatings. However, the poor wettability of hBN with most materials makes it difficult to fabricate NiCr–Cr3C2-hBN composite coating with good cohesion strength. In this study, hBN was firstly pretreated through magnetron-sputtering aided Ni plating to form hBN@Ni particles. Then, NiCr–Cr3C2-hBN@Ni powder was prepared by spray granulation. Next, corresponding coatings were prepared through supersonic atmosphere plasma spraying. It was found that in comparison with NiCr–Cr3C2-hBN coating, the NiCr–Cr3C2-hBN@Ni coating exhibited a decreased porosity (from 3.6% to 0.3%), elevated cohesion (from 52.78 N to 62.11 N), and the wear rate decreased by an order of magnitude. It was concluded that hBN@Ni can effectively improve the component interface inside powder, enhance the cohesion of molten in-flight particles, and make the internal structure of the coating denser.  相似文献   

3.
《Ceramics International》2017,43(9):7295-7304
Al2O3-40 wt%TiO2 (AT40) coating is a low-cost and widely applied ceramic coating. In this article, the phase distribution, micro-hardness and wear mechanism, as well as the spraying conditions optimization, are discussed. Interface defects. Phase distribution and phase composition were analysed using SEM and XRD. The results show that the pre-existing surface morphology mainly determines the phase distribution. Al2TiO5 and γ-Al2O3 are the main phases in the coating. In this experiment, the highest micro-hardness (1126.2 HV0.2) was measured using a Vickers tester. Additionally, the wear rate of the highest micro-hardness coating is 0.0387 mg/N m, which is the lowest weight loss rate measured among all the samples. The wear mechanism for this sample is primarily scratches. In conclusion, the compact lamellar phase distribution decreases the number of interface defects, increases the hardness and determines the wear mechanism. Also, the phase distribution is affected by the spraying conditions.  相似文献   

4.
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   

5.
《Ceramics International》2020,46(8):11799-11810
The effect of Y2O3 addition on structure, mechanical properties and tribological properties of Al2O3-13 wt% TiO2 coating was investigated. The addition of 20 wt% Y2O3 resulted in better densification, stabilization of alpha (α) alumina phase and improvement in fracture toughness of Al2O3-13 wt% TiO2 coating. Abrasive wear tests were performed over a range of loads and sliding speeds. The stabilization of α alumina phase further increased with an increase in severity of wear test conditions, as noted from X-Ray Diffraction (XRD) and X-Ray Photoelectron Spectroscopy (XPS) analysis of worn coatings. Al2O3-13 wt% TiO2-20 wt% Y2O3 coating displayed lower friction coefficient and lower abrasive wear rate than Al2O3-13 wt% TiO2 coating, which was due to synergistic effect of α alumina phase and formation of magneli phase oxide of titanium; Ti2O3. Friction energy map was used to rationalize observed wear rates, to identify different regimes of wear and degradation modes of coatings.  相似文献   

6.
Al2O3-Y2O3-SiC composite coatings were prepared on depleted uranium by cathode plasma electrolytic deposition in Al(NO3)3, Y(NO3)3, SiC nanoparticles and anhydrous ethyl alcohol mixture. The resulting coating consisted of an inner barrier layer and an outer porous layer. The SiC nanoparticles were incorporated into the composite coating and decreased the coating porosity by filling the pores. The potentiodynamic polarization test and neutral salt spray test revealed that the corrosion resistance of depleted uranium was enhanced by the composite coating. Moreover, with increasing the content of SiC nanoparticles in the coating, the coating corrosion resistance was improved gradually.  相似文献   

7.
In this work, ZrC-SiC-Yb2O3 ternary composite coatings with different contents of Yb2O3 (0, 5, 15 and 30 wt.%) were fabricated by vacuum plasma spray and the anti-ablation property above 2000 °C was evaluated. The results showed that the microstructures of the oxide scales were changed with different Yb2O3 contents and then greatly modified the ablation resistant property of the composite coatings. The composite coating with 15 wt.% Yb2O3 exhibited the best ablation resistance. The disappearance of SiC-depleted layer and formation of ZrCxOy were observed. The mechanism of Yb2O3 on the oxidation products and ablation behaviors of ZrC-SiC system was analyzed.  相似文献   

8.
《Ceramics International》2020,46(3):2901-2909
In this work, a Cu-incorporated Al2O3 coating has been successfully produced through the one-step plasma electrolytic oxidation (PEO) method. Unexpectedly, the resultant Cu-incorporated Al2O3 coating displays a multi-layered structure, which exhibits significant variations in morphology, composition and crystallinity. Compared to the compact outer layer of the PEO coating, both medium and inner layers are highly porous even the average pore size of the medium layer is obviously higher than that of the inner layer. The medium layer has a higher Cu content in comparison to both outer and inner layers. And the outer layer mainly consists of crystalline γ-Al2O3 phase whereas both medium and inner layers are in amorphous states. Further, it was found that Cu specie could exist as Cu2O and CuO in the Cu-incorporated PEO coating. Finally, it was revealed that the incorporation of Cu into the porous PEO coating significantly improves the antifouling property of Al metallic substrate against SRB, which successfully prevents the formation of SRB biofilm. Hence, PEO method is a promising surface modification technique for the fabrication of antifouling coating.  相似文献   

9.
The damping capacity of plasma sprayed alumina (Al2O3) coatings on AISI 304 stainless steel was investigated in this study as a function of particle size of the starting alumina powder. The coatings were prepared from different sizes alumina powder using commercial air plasma spraying (APS) technique. The damping properties of coated samples were characterized by damping capacity (Q?1) measured experimentally using dynamic mechanical analyzer (DMA). The surface morphology of the coatings was studied using scanning electron microscope (SEM). The results revealed that the coating was porous and was able to improve the damping capacity of bare substrate. It was also observed that the powder particle size had a significant effect on the damping characteristics of the coatings. The damping values were found to be increased with the increase in particle size in the measured strain range. This behaviour was correlated with the microstructure investigated by SEM.  相似文献   

10.
Ceramic coatings were prepared on 6061 Al alloy in a mixed electrolyte with/without MgO powders at different treatment durations. The results of energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) showed that MgO powder was incorporated into the coatings, and Mg species gradually aggregated into coating inside as prolonging the oxidation time. Scanning electron microscopy (SEM) showed that MgO additive had a certain effect on the microstructures and coating thickness. The corrosion behavior tests evaluated by potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) in 3.5 wt% NaCl solution suggested that at the same treatment time, the addition of MgO powders can improve the corrosion resistance of the coating, and the Mg-rich layer can affect the corrosion resistance of the coating. The tests of mechanical properties showed that the addition of MgO powders improved the stability and hardness of the coating.  相似文献   

11.
In this study, Al2O3-TiB2 coating was successfully deposited on steel substrates by in situ plasma spraying (IPS) using H3BO3, Al, and TiO2 reactants. Beside TiB2 and Al2O3, Al18B4O33 was formed as a by-product with ratio of about 13 wt%. The effect of milling time of reactant and the reaction behavior was also explored. Milling process for at least 10 h can promote efficiency of reaction and milling for efficient production of Al2O3-TiB2 composite. Wear behavior was examined in terms of hardness, wear track width, and wear rate of the coatings with respective measured values of 797.6 HV, 1061.3 µm, and 4.2 × 10−3 mm3/N.m. Based on the FESEM observations, the thickness of abrasive coating was 417 µm, delamination and adhesion were the main wear mechanisms in Al2O3-TiB2-coated specimens.  相似文献   

12.
以氧化铝溶胶为前驱体,采用电泳沉积和低温煅烧法在低碳钢基体上制备了氧化铝陶瓷涂层,并对其成分、表面形貌及耐蚀性进行了研究。结果表明,将低碳钢片置于以乙醇作为分散介质的0.45mol/L氧化铝溶胶中,在60V恒电位下沉积180s后,再于马弗炉中700°C下煅烧5min,所制得的氧化铝陶瓷涂层在2mol/L盐酸溶液中具有良好的耐蚀性。  相似文献   

13.
Recently, a technique for improving the thermal efficiency of automotive engines has received considerable attention, namely the application of thermal insulation coatings to automotive engine components to reduce heat loss. This study presents thermal shock resistance and related microstructural changes and thermal properties of 8 wt% yttria-stabilized zirconia (8YSZ)/SiO2 multi-compositional thermal insulation coatings with suspensions of various particle sizes, when subjected to suspension plasma spray. After 10,000 cycles of thermal shock testing of the coatings, it was found that different degradation behavior related to the different microstructure of the coatings was influenced by the particle sizes of the suspension. The thermal conductivity of the coatings was significantly reduced by increasing the distribution of the unmelted particles within the coating.  相似文献   

14.
《Ceramics International》2017,43(5):4037-4041
The solidification mechanism and microstructure of the hypoeutectic Al2O3-ZrO2 (Al2O3:72 mol%) ultra-fined ceramic coating prepared by combustion synthesis and rapid plate cooling method were analyzed by the heat transfer process and dynamic characteristics. The rapid solidification process inhibited the transformation from the t-ZrO2 to m-ZrO2 at low temperatures. The growth rate of the solid-liquid interface to form the amorphous and nano-crystalline Al2O3-ZrO2 was about 65.7 mm/s and 13.7 mm/s, respectively. The mechanism formation of both the amorphous and nano-crystalline areas were analyzed using rapid solidification models. When the growth rate reduced to about 8.23 mm/s, large quantities of nanosized eutectic structures was identified by SEM in the pseudo-eutectic area. The interphase spacing of the eutectic structures was 40–100 nm. In addition, some typical divorced eutectic structures appeared at this area. After that, micron dendrites (0.2–0.6 µm) took the main part when the growth rate decreased to about 3.67 mm/s for such a hypoeutectic Al2O3-ZrO2 binary system. The nano-crystalline area showed the highest nanohardness (22 GPa). This paper may provide new guidance to prepare high performance Al2O3-ZrO2 ceramics both in experiment and theory.  相似文献   

15.
《Ceramics International》2022,48(24):36539-36555
In this study, La1-xNdxMgAl11-xScxO19 (x = 0.1, 0.2, 0.3; abbreviated as LNMAS-1, 2, 3) coatings which are supposed to possess better properties than LaMgAl11O19 (LMA) were plasma-sprayed and their high-temperature performance were comparatively investigated. Results show that addition of Nd3+ and Sc3+ as dopants to LMA endows corresponding coatings with reduced thermal conductivity and enhanced thermal expansion coefficient, while maintaining advantageous phase stability, although still being subjected to amorphization in plasma flame and following crystallization upon high-temperature service. Furthermore, the doping could cause adherence increasing between topcoat/bondcoat, benefiting from improved melting condition, especially in LNMAS-2 and LNMAS-3 coatings, which is related to the specific powder morphology and lowered melting point. During exposure to 1350°C, mechanical performance and structure integrity of doped free-standing LNMAS coatings can be well preserved even after 400 h aging. In thermal cyclic fatigue test, LNMAS-2 and LNMAS-3 coatings undertake thermal cycling lifetime of ~181 and 191 cycles at 1100°C, respectively, 40% durable than that of LMA coating. These preliminary results suggest that LNMAS-2, 3 might be promising candidates for advanced thermal barrier coating applications.  相似文献   

16.
《Ceramics International》2023,49(5):7589-7599
To investigate the effects of air annealing on the microstructure, components, and mechanical properties of ceramic composite coatings, Al2O3–Cr2O3–ZrO2 composite coatings were prepared on silicon substrate using radio frequency magnetron sputtering at room temperature, and then air-annealed in a temperature range of 450–850 °C for 30 min. The results indicated that the phase-structure and superficial characteristics, including morphology and surface roughness, were not visibly altered in the annealed coatings up to 600 °C; the elemental component distributions remained uniform. The improvement in the mechanical properties was attributed to the growth of oxide grains. There were no significant changes in the components of Al, Cr, Zr, and O in the annealed coatings. However, an increase in the Cr component and a decrease in the Zr component occurred on the coating surface; the overall structure of the composite coatings possessed a favorable heat resistance. Upon annealing at 750 °C, the thermally-driven formation of uniform and refined nanoparticles on the coating surface was responsible for the effective enhancement of the mechanical properties. Furthermore, annealing at 850 °C induced the enlargement of the precipitated Cr2O3 nanoparticles and the generation of micro-defects, resulting in a drastic morphological evolution, an evident increase in the surface roughness, and a significant decrease in the mechanical properties. This study provides new perspectives on designing novel thermal barrier coatings and understanding the role of high temperature air annealing on the microstructural transformation.  相似文献   

17.
Aluminum acetylacetonate (Al(acac)3) was used as a precursor to synthesize aluminum oxide (Al2O3) coatings on Ti(C, N)-based ceramic by microwave plasma CVD (MPCVD). Al2O3 coatings transformed from γ phase to δ phase and α phase and as microwave power (pM) and total pressure (Ptot) increased. The effects of pM and Ptot on the microstructure of the Al2O3 coating and oxidation of the substrate have been investigated. The relationship between phase structure and adhesive strength of the coatings was also studied. Coatings deposited at pM = 1.0-1.2 kW and Ptot = 400 Pa exhibited good adhesion strength (Class 1).  相似文献   

18.
To obtain composite ceramics with excellent thermal shock resistance and satisfactory high?temperature service performance for solar thermal transmission pipelines, SiC additive was incorporated into Al2O3?mullite?ZrO2 composite ceramics through a pressureless sintering process. The effect of the SiC additive on thermal shock resistance was studied. Also, the variations in the microstructure and physical properties during thermal cycles at 1300 °C were discussed. The results showed that both thermal shock resistance and thermal cycling performance could be improved by adding 20 wt% SiC. In particular, the sample with 50 wt% Al2O3, 35 wt% Coal Series Kaolin (CSK), 15 wt% partially yttria?stabilized zirconia (PSZ), and 20 wt% SiC additional (denoted as sample A2) exhibited the best overall performance after firing at 1600 °C. Furthermore, the bending strength of sample A2 increased to 124.58 MPa, with an increasing rate of 13.63% after 30 thermal shock cycles. The increase in thermal conductivity and the formation of mullite were the factors behind the enhancement of thermal shock resistance. During the thermal cycles, the oxidation of SiC particles was favorable as it increased the microstructure densification and also facilitated the generation of mullite, which endowed the composite ceramics with a self?reinforcing performance.  相似文献   

19.
《Ceramics International》2022,48(10):13914-13926
Laser treatment (LT) to enhance the performance of atmospheric plasma spray (APS) deposited Al2O3 thermal barrier coatings (TBCs) was attempted for applications in extreme liquid-sodium environments of a sodium-cooled fast reactor (SFR). Thermally sprayed sacrificial ceramic TBCs are being proposed and investigated for installation on the stainless steel (SS) 316LN core catcher assembly of future SFRs to combat the core disruptive accidents (CDAs), wherein the primary criterion to be satisfied by the TBC is its long-term compatibility with the liquid-sodium coolant over a whole reactor life. Sacrificial ceramic coatings are susceptible to liquid-metal induced degradation by reactor-grade sodium. This study provides new insights into the failure mechanisms of APS Al2O3 coatings in liquid-sodium environments. Subsequently, an attempt is made to improve the performance of coatings by a surface modification approach using a laser treatment of the TBC topcoat. APS coatings exposed to liquid-sodium failed by spallation and delamination of the incrementally deposited topcoat, which is attributed to the formation and growth stress of ternary Na–Al oxides between the lamellar layers of the APS coatings. Compared to the APS coatings, LT coatings successfully retarded the liquid-sodium ingression and thereby exhibited improved degradation resistance and structural stability in reactor simulated sodium environments. The enhanced performance of LT coatings is attributed to its carefully re-engineered architecture of the APS TBC that could beneficially control the kinetics of interaction with liquid-sodium.  相似文献   

20.
《Ceramics International》2022,48(16):23510-23517
In the present work, microstructural refinement and mechanical response of Al2O3–ZrO2 eutectics fabricated by a pulse discharge plasma assisted melting (PDPAM) method were investigated. The solidified microstructure evolves from polygonal eutectic colonies into irregular cellular colonies with increasing the superheating temperature of the melt from 1820 °C to 1900 °C. The average eutectic spacing inside the colonies decreases from 1.80 ± 0.10 μm to 0.25 ± 0.06 μm, and the coarse inter-colonial structure is refined, which is attributed to the increase in undercooling temperature. High-temperature microstructural stability of Al2O3–ZrO2 eutectics is improved significantly as contrasted with the as-sintered ceramics. Besides, the load dependence of Vickers hardness for Al2O3–ZrO2 eutectics is investigated.  相似文献   

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