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1.
To enhance the bonding between hydroxyapatite (HA) coating and titanium alloy substrate, HA/TiO2 composite coatings have been fabricatedvia plasma spraying. Bonding strength evaluation, simulated body fluid tests, and cell culturein vitro were carried out to characterize the composite coatings. The results obtained showed that the addition of TiO2 to HA coating improved the bonding strength of the coating significantly. After being immersed in simulated body fluid (SBF)
for a period, the surfaces of HA/TiO2 composite coatings were completely covered by carbonate-containing apatite, which indicated that the coatings possess good
bioactivity. Thein vitro cell culture indicated good cytocompatibility for HA/TiO2 composite coatings. 相似文献
2.
Mechanical and tribological properties of plasma-sprayed Cr3C2-NiCr, WC-Co, and Cr2O3 coatings 总被引:1,自引:0,他引:1
Mechanical properties such as Young’s moduli and fracture toughness of plasma-sprayed Cr3C2-NiCr, WC-Co and Cr2O3 coatings were measured. The tribological properties of the three kinds of coatings were investigated with a block-on-ring
self-mated arrangement under water-lubricated sliding. Furthermore, the influences of the mechanical properties on the tribological
properties of the coatings were also examined. It was found that the Young’s moduli, bend strengths and fracture toughness
of the coatings were lower than the corresponding bulk materials, which may be attributed to the existence of pores and microcracks
in the coatings. Among the three kinds of coatings, the magnitude of wear coefficients, in decreasing order, is Cr3C2-NiCr, WC-Co and Cr2O3, and the wear coefficient of Cr2O3 coating was less than 1 × 10−6mm3N−1m−1. The wear mechanisms of the coatings were explained in terms of microcracking and fracturing, and water deteriorated wear
performance of the coatings. The higher the fracture toughness and the lower the porosity and length of microcracking of the
coating, the more the wear-resistance of the coating. 相似文献
3.
Voramon S. Dheeradhada David R. Johnson Mysore A. Dayananda 《Journal of Phase Equilibria and Diffusion》2006,27(6):582-589
Diffusional analyses were performed to understand the oxidation at 1300 °C of a multiphase Mo-13.2Si-13.2B (at.%) alloy. During
oxidation, a protective glass scale formed with an intermediate layer of (Mo+glass) between the base alloy and external glass
scale. Compositional profiles across the (Mo+glass) layer and the external glass scale were determined, and interdiffusion
fluxes and effective interdiffusion coefficients for the various components were determined by using “MultiDiFlux” software. The motion of the (alloy/Mo+glass) and (Mo+glass/glass) interphase boundaries after passivation was examined.
Additionally, vapor-solid diffusion experiments at 1300 °C were carried out with single-phase Mo3Si and T2 specimens in addition to a multiphase Mo-10Si-10B (at.%) alloy. These specimens were exposed to vacuum to induce
silicon loss resulting in the formation of a Mo layer. An average effective interdiffusion coefficient of Si in Mo at 1300
°C was estimated from the Mo3Si-vapor couple to be in the order of 8×10−17 m2/s.
This article was presented at the Multicomponent-Multiphase Diffusion Symposium in Honor of Mysore A. Dayananda, which was
held during TMS 2006, 135th Annual Meeting and Exhibition, March 12–16, 2006, in San Antonio, TX. The symposium was organized
by Yongho Sohn of University of Central Florida, Carelyn E. Campbell of National Institute of Standards and Technology, Richard
D. Sisson, Jr., of Worcester Polytechnic Institute, and John E. Morral of Ohio State University. 相似文献
4.
hBN含量对等离子喷涂NiCr/Cr_3C_2-hBN复合涂层力学性能的影响 总被引:1,自引:0,他引:1
采用化工冶金包覆、喷雾造粒和固相合金化技术以Cr3C2和hBN为核心制备了NiCr/Cr3C2-h BN复合粉体,并用等离子喷涂技术制备了NiCr/Cr3C2-hBN涂层,研究了涂层的显微结构、物相组成、显微硬度和结合强度。研究结果表明,等离子喷涂NiCr/Cr3C2-h BN复合涂层呈典型的层状结构,各层之间结合良好。涂层的显微硬度和结合强度均随hBN含量的增加逐渐降低,当hBN含量为20%时,涂层的显微硬度和结合强度分别为NiCr/Cr3C2涂层的66%和50%。涂层断裂位置发生在涂层内部,为典型的脆性断裂。 相似文献
5.
采用化工冶金包覆、固相合金化和喷雾造粒技术制备了NiCr/Cr3C2复合粉体,并采用大气等离子喷涂技术制备了NiCr/Cr3C2复合涂层,采用SEM、显微硬度计、万能试验机和马弗炉对粉体和涂层的显微结构、涂层的显微硬度、结合强度和氧化性能进行了分析。结果显示:NiCr/Cr3C2涂层呈典型的层状结构,各层间结合良好,结合强度为(27.4±5) MPa,涂层显微硬度约850 HV0.2,为结合层显微硬度的2.7倍,涂层为典型的脆性断裂,断裂的位置发生在涂层的层与层之间。NiCr/Cr3C2涂层850 ℃氧化动力学曲线基本符合抛物线氧化规律。在氧化过程中涂层表面生产了氧化膜,且氧化膜会发生脱落,同时涂层内部出现了偏析现象,析出了金属Cr。 相似文献
6.
针对纯陶瓷涂层由于结合强度低、孔隙率高、影响涂层耐磨性的实际,用等离子喷涂法制备了Cu-Al2O3梯度涂层,用电子扫描显微镜(SEM)、金相显微镜等手段对涂层进行微观组织和成分分析,用自制销盘式固定磨料磨损试验机,检测了Cu-Al2O3梯度涂层的耐磨料磨损性能.结果表明,采用等离子喷涂法制备的Cu-Al2O3梯度涂层无明显的组织突变和宏观层间界面,涂层的组织表现出宏观不均匀性和微观连续性分布特征;梯度涂层中当Al2O3含量(质量分数,%)达到80%时(GC6),涂层的耐磨性最高,约为基体的3倍,随着Al2O3含量继续增大,纯陶瓷涂层(GC7)的耐磨性有所下降. 相似文献
7.
Plasma-sprayed Al2O3 coatings contain both metastable and stable phases of Al2O3. The formation of these phases is influenced by various process parameters, such as stand-off distance (SOD), gas flow rates, nozzle diameter and is also dependent on the melting and solidification behaviour of feedstock particles, as these help in controlling the weight fraction of different phases formed in the coating. The present work reports the investigation on the effect of two major plasma spray parameters, namely secondary gas (H2) flow rate and SOD, on the formation of phases in plasma-sprayed Al2O3 coating. The phases were identified by X-ray diffraction analysis and to quantify those phases, the Rietveld refinement method was used. The influence of α-phase on the mechanical properties of the Al2O3 coatings was evaluated, and it has been observed that α-phase content decreases with the increase in secondary gas flow rate. With the increase in SOD, the α-Al2O3 phase content first decreases and then increases. 相似文献
8.
WCp/NiCrBSi composite coatings have been deposited by plasma spraying with the mixed powders of WC-12Ni and NiCrBSi. The coatings consist mainly of WC, γ-Ni, Ni3B, CrB, Cr2B, M7C3, M23C6 and W2C phases. The W2C content increases with increasing WC mass fraction in the powders. The porosity and microhardness of the coatings are related to the coating WC content. The excessive WC results in decreasing the microhardncss due to increasing the porosity. The WCp/ NiCrBSi coating with 35 % WC mass fraction powder has more excellent erosion resistance. With an increase of impact angles from 15°to 90°the erosion rate of the coating increases, the erosion rate at 15°impact angle being approximately two times lower than that at 90°impact angle. Based on the wear morphology of the coatings at different impact angles, the wear mechanisms were discussed. 相似文献
9.
A CO2 laser with cylindrical focal lens has been used to glaze the surface layer of plasma-sprayed ZrO2-20wt% Y2O3/MCrAlY coatings. Both a continuous-wave laser and a pulsed laser were used in this study. Different parameter settings for
power, travel speed, and pulse frequency were used, and their effects on the melting width, melting depth, coupling efficiency,
microstructure, surface roughness, and process defects have been evaluated. Results show that the melting width of the glazed
track was slightly smaller than the diameter of the raw beam. The melting depth increased with increasing energy density for
both a continuous-wave laser and a pulsed laser. The coupling efficiency as about 40 to 65% for a continuous-wave laser, which
increased with increasing laser travel speed, but decreased with an increase in energy density. The power density has no significant
effect on coupling efficiency. Defects, such as bubbles or depressions, occur easily with a continuous wave laser. A high-quality
glazed layer is successfully produced using a pulsed laser. The surface roughness of the plasma-sprayed ceramic coatings was
significantly improved by laser glazing. Surface roughness decreased slightly as the pulse frequency increased for the glazed
surface. Based on this study, proper processing parameters have been suggested. 相似文献
10.
Shunyan Tao Bo Liang Chuanxian Ding Hanlin Liao Christian Coddet 《Journal of Thermal Spray Technology》2005,14(4):518-523
Reconstituted nanostructured and conventional yttria partially stabilized zirconia coatings were deposited by atmospheric
plasma spray. The tribologic properties of the coatings against 100C6 steel were evaluated with a ball-on-disc configuration
under dry friction conditions at room temperature. Microstructure and the phase composition of the powders and the coatings
were examined using a scanning electron microscope, optical microscope, and x-ray diffraction. Microhardness and the Young’s
modulus of coatings were measured by indentation testing. Results showed that the wear resistance of the coatings produced
using the nanostructured powder is improved compared with the coating produced using the conventional powder. The wear rates
of nanostructured zirconia coatings are about four-fifths of those of conventional counterparts under a load of 5 N. The wear
mechanism is also discussed.
The original version of this paper was published as part of the DVS Proceedings: “Thermal Spray Solutions: Advances in Technology
and Application,” International Thermal Spray Conference, Osaka, Japan, 10–12 May 2004, CD-Rom, DVS-Verlag GmbH, Düsseldorf,
Germany. 相似文献
11.
The cross-sectional analysis on hydroxyapatite (HA) coating and HA TiO2 composite coating was conducted by using electron probe microanalyser (EPMA). The results reveal that annealing at 650℃ leads to the cracking within the HA coating or along the coating/substrate interface. The ribbon-like regions in HA coating are verified to contain less PO4^4- groups resulted from the high temperature melting of HA particles in plasma flame. From the viewpoint of microstructural observation, it can be concluded that the addition of TiO2 into HA coating can effectively strengthen and toughen the whole coating system with a shift of the well-bonded interface from the THA (top HA) coating/HTBC (HA TiO2 bond coat) interface in the as-sprayed THBC (top HA-HTBC) coating to the HTBC/Ti substrate interface in the heat treated THBC coating. The THA coating bonds well to Ti substrate per-haps via its TiO2 hobnobbing with the Ti oxides formed on the Ti substrate. 相似文献
12.
The failure mechanisms of thermal barrier coatings (TBCs) subjected to a thermal load are still not entirely understood. Thermal
stresses and/or oxidation cause the coating to fail and hence must be minimized. During the present investigation, TBCs up
to 1.0 mm were sprayed and withstood high thermal stresses during thermal testing. Owing to the substantial thickness, the
temperature at the top coat/bond coat interface was relatively low, resulting in a low oxidation rate. Furthermore, bond coats
were preoxidized before applying a top coat. The bond strength and the behavior during three different thermal loads of the
preoxidized TBCs were compared with a standard duplex TBC. Finite-element model (FEM) calculations that took account of bond
coat preoxidation and interface roughness were made to calculate the stresses occurring during thermal shock. It is concluded
that the thick TBCs applied during this research exhibit excellent thermal shock resistance and that a preoxidizing treatment
of the bond coat increases the lifetime during thermal loading, where oxidation is the main cause of failure. The FEM analysis
gives a first impression of the stress conditions on the interface undulations during thermal loading, but further development
is required. 相似文献
13.
N. Branland E. Meillot P. Fauchais A. Vardelle F. Gitzhofer M. Boulos 《Journal of Thermal Spray Technology》2006,15(1):53-62
Relationships between electrical properties of thermally sprayed titania coatings and their microstructures have been investigated.
It is well known that the quality and properties of the plasma-sprayed coatings are strongly dependent on the in-flight particle
characteristics, which directly influences the plasma-sprayed coating microstructures. As far as possible, a broad range of
microstructures was produced by using various processes of plasma spraying with different powder size ranges and variation
of the plasma operating parameters. The two plasma-spraying processes consisted of direct current (DC) and radio frequency
(RF) plasma spraying. The major concern of the study was that plasma-sprayed parameters influence also the stoichiometry of
the titania coating resulting in a large variation of their electrical properties. It is the reason why coatings with identical
stoichiometry were compared. The comparison between RF and DC plasmasprayed titania coatings highlighted that electrical resistivity
was directly linked to the quality of the contact between the splats and their density through the titania plasma-sprayed
coatings. 相似文献
14.
不同燃料超音速火焰喷涂NiCr-Cr3C2涂层 总被引:1,自引:0,他引:1
采用超音速火焰喷涂工艺在20CrMo钢圆片上成功制备25%NiCr-Cr3C2金属陶瓷涂层,研究了不同燃料对喷涂层组织性能的影响。结果表明,以丙烷为主要燃料所得喷涂层的组织不均匀,存在典型的层状结构,孔隙率约为3.2%,显微硬度仅为836 HV,涂层断裂韧性KIC为2.08 MPa.m3/2;以煤油为主要燃料所得喷涂层的组织分布均匀,细小致密,孔隙率约为2.4%,显微硬度可达1045 HV,涂层断裂韧性KIC为2.56 MPa.m3/2。前者的组成相为Ni(Cr)固溶体、Cr3C2和微量NiCrO4;后者的组成相除Ni(Cr)固溶体和Cr3C2外,还有Cr7C3、Cr23C6和Ni(Cr)相出现。 相似文献
15.
A ball-milled mixture of glass and alumina powders has been plasma sprayed to produce alumina-glass composite coatings. The
coatings have the unique advantage of a melted, ceramic secondary phase parallel to the surface in an aligned plateletlike-composite
structure. The alumina raises the hardness from 300 HV for pure glass coatings to 900 HV for a 60 wt.% alumina-glass composite
coating. The scratch resistance increases by a factor of 3, and the wear resistance increases by a factor of 5. The glass
wears by the formation and intersection of cracks, while the alumina wears by fine abrasion and supports most of the sliding
load. The wear resistance reaches a maximum at 40 to 50 vol.% alumina, above which there is little further improvement. This
critical alumina content corresponds to the changeover from a glass to a ceramic matrix. 相似文献
16.
The photoelectrochemical characteristics of plasma-sprayed porous TiO2, TiO2-5%ZnO, and TiO2-10%ZnO electrodes in 0.1 N NaOH solution were studied through a three-electrode cell system. The microstructure, morphology,
and composition of the electrodes were analyzed using an electron probe surface roughness analyzer (ERA-8800FE), scanning
electron microscopy, and x-ray diffraction. The results indicate that the sprayed electrodes have a porous microstructure,
which is affected by the plasma spray parameters and composition of the powders. The TiO2-ZnO electrodes consist of anatase TiO2, rutile TiO2, and Zn2Ti3O8 phase. The photoresponse characteristics of the plasma-sprayed electrodes are comparable to those of single-crystal TiO2, but the breakdown voltage is close to 0.5 V (versus that of a saturated calomel electrode). The short-circuit photocurrent
density (J
SC) increases with a decrease of donor concentration, which was calculated according to the Gartner-Butler model. For the lowest
donor concentration of a TiO2-5%ZnO electrode sprayed under an arc current of 600 A, the short-circuit J
SC is approximately 0.4 mA/cm2 higher than that of the TiO2 electrodes under 30 mW/cm2 xenon light irradiation. The J
SC increases linearly with light intensity.
The original version of this paper was published as part of the DVS Proceedings: “Thermal Spray Solutions: Advances in Technology
and Application,” International Thermal Spray Conference, Osaka, Japan, 10–12 May 2004, CD-Rom, DVS-Verlag GmbH, Düsseldorf,
Germany. 相似文献
17.
Al2O3, Al2O3-Cr2O3 and Cr2O3 coatings were deposited by atmospheric plasma spraying. Phase composition of powders and as-sprayed coatings was determined by X-ray diffraction. Electron probe microanalyzer was employed to investigate the polished and fractured surface morphologies of the coatings. Mechanical properties including microhardness, fracture toughness and bending strength were evaluated. The results indicate that the addition of Cr2O3 is conducive to the stabilization of α-Al2O3. Compared with the pure Al2O3 and Cr2O3 coatings, Al2O3-Cr2O3 composite coatings show lower porosities and denser structures. Heterogeneous nucleation of α-Al2O3 occurs over the isostructural Cr2O3 lamellae and partial solid solution of Al2O3 and Cr2O3 might be occurring as well. Furthermore, grain refining and solid solution strengthening facilitate the mechanical property enhancement of Al2O3-Cr2O3 composite coatings. 相似文献
18.
采用普通Metco 130粉末及纳米结构Al2O3-13% TiO2粉末通过等离子喷涂和激光重熔复合技术分别在Ti-6Al-4V合金表面制备了激光重熔涂层.采用扫描电镜(SEM)和维氏硬度计等手段观察和研究了激光重熔前后涂层的微观组织和硬度.结果表明,激光重熔后,消除了等离子喷涂涂层的层状结构,获得了致密的重熔涂层,且纳米结构重熔涂层传承了喷涂态涂层的双模态组织特征.随着扫描速度的降低,涂层表面的致密度提高.纳米结构重熔涂层的硬度为1150 HV0.3至1750 HV 0.3,比重熔之前的喷涂态涂层约提高了60%. 相似文献
19.
F. Grtner T. Stoltenhoff J. Voyer H. Kreye S. Riekehr M. Koak 《Surface & coatings technology》2006,200(24):6770-6782
The present investigation compares the mechanical properties of cold-sprayed and thermally sprayed copper coatings. The mechanical properties of the Cu-coatings are determined by in plane tensile test using micro-flat tensile specimen technique. A deeper view into the type of obtained defects, their stability and their influence on coating performance, is supplied by subsequent failure analyses and the comparison to annealed copper coatings. The results demonstrate that cold-sprayed coatings, processed with helium as propellant gas, show similar performance as highly deformed bulk copper sheets and respective changes in properties after annealing. In the as-sprayed condition, cold-sprayed coatings processed with nitrogen and thermally sprayed coatings show rather brittle behavior. Whereas subsequent annealing can improve the properties of the cold-sprayed coating, processed with nitrogen, such heat treatments have only minor influence on the tensile properties of thermally sprayed copper coatings. The investigation of failure modes for the as-sprayed states and after different heat treatments provided further information concerning particle–particle bonding and the effect of oxides on mechanical properties. 相似文献
20.
H. R. Salimijazi T. W. Coyle J. Mostaghimi L. Leblanc 《Journal of Thermal Spray Technology》2005,14(3):362-368
In the present study, boron carbide was deposited on Ti-6%Al-4%V alloy by vacuum plasma spraying. Chemical and phase compositions
of the initial starting powder and the as-sprayed deposit were characterized using hot gas extraction, x-ray photoelectron
spectroscopy, Raman spectroscopy, x-ray diffraction, and transmission electron microscopy. Mechanical properties of the deposition
were assessed by microhardness and nanohardness indentation. The microstructure consisted of equiaxed boron carbide grains,
microcrystalline particles, and amorphous carbon regions. The amount of boron oxide and amorphous carbon in the coating was
increased compared with the initial powder. The measured microhardness was slightly higher than values reported previously
(1033±200 HV). There was significant variation in measured nanohardness (−100 + 39 GPa) from point to point caused by multiple
phases, splat boundaries, and porosity in the deposited structure. Carbon segregation to grain boundaries and/or splat boundaries
in boron carbide was observed directly using spatially resolved electron energy loss spectroscopy method. 相似文献