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1.
Plasma spray forming of tungsten coatings on copper electrodes 总被引:3,自引:1,他引:3
蒋显亮 《中国有色金属学会会刊》2004,14(5):835-839
Both direct current dc plasma and radio frequency induction plasma were used to deposit tungsten coatings on copper electrodes. Fine tungsten powder with mean particle size of 5 um and coarse tungsten powder with particle size in the range from 45 um to 75 um were used as plasma spray feedstock. It is found that dc plasma is only applicable to spray the fine tungsten powder and induction plasma can be used to spray both the coarse powder and the fine powder. The tungsten coating deposited by the induction plasma spraying of the coarse powder is extremely dense. Such a coating with an interlocking structure and an integral interface with the copper substrate demonstrates high cohesion strength and adhesion strength. 相似文献
2.
冷喷涂TC4涂层临界沉积速度计算及制备涂层性能研究 总被引:1,自引:1,他引:0
目的研究冷喷涂TC4涂层的临界沉积速度及粒子温度对临界沉积速度的影响规律,并研究气体压强对沉积涂层性能的影响规律。方法理论研究上,采用有限元LS-DYNA软件中的Johnson-Cook塑性模型,选取3D164计算单元建立模型,研究粒子在不同温度和不同速度下碰撞基体后的形貌特征,确定粒子沉积临界速度。试验研究上,采用N_2作为冷喷涂驱动气体,在TC4合金上制备TC4涂层,然后采用SEM、Image J图像分析软件、硬度计等分析已沉积涂层的孔隙率和硬度等性能。结果 25、400、500、600℃温度下,计算表明10μm的TC4合金粒子在TC4基板上的临界沉积速度分别为730、465、392、361 m/s,即随粒子温度升高,粒子临界沉积速度降低,粒子沉积成涂层更容易。采用冷喷涂工艺在TC4基板上沉积TC4涂层,在N_2温度600℃、气体压力3 MPa的条件下,制备的TC4涂层厚度约1000μm,与TC4钛合金基体结合紧密,涂层孔隙率约为6.46%。结论气体温度升高,粒子临界沉积速度降低;气体压强变大,制备的涂层厚度就大且更加致密。 相似文献
3.
4.
The Influence of the Substrate on the Deposition of Cold-Sprayed Titanium: An Experimental and Numerical Study 总被引:1,自引:0,他引:1
D. K. Christoulis S. Guetta V. Guipont M. Jeandin 《Journal of Thermal Spray Technology》2011,20(3):523-533
The deposition of cold-sprayed titanium on various substrates is studied in this work. A rather coarse powder of titanium
(−70 + 45 μm) was sprayed under uniform spraying conditions using a cold spray system onto five different substrates: two
aluminum-based alloys (AISI 1050-H16 and AISI 2017-T4), copper, stainless steel AISI 304L, and Ti-6Al-4V. All the spraying
experiments were carried out using alternatively nitrogen (N2) or helium (He) as the process gas. Thick coatings were formed on the various substrates, with the exception of the AISI
2017 substrate. When N2 was used as the process gas, only a few particles remained adhering to the AISI 2017. The thick pre-existing superficial
oxide layer on AISI 2017, which was detected by Electron MicroProbe Analysis (EPMA), appeared to prevent adhesion of cold-sprayed
titanium particles. The interaction of the sprayed particles with the various substrates was also studied by means of numerical
simulations to better understand the adhesion mechanisms. The microstructure and the characteristics of the coatings were
investigated. Deposition efficiency and coating density were found both to be strongly improved by spraying helium as the
process gas. 相似文献
5.
Composite coatings of a Ti-B-C system were reactively produced by the electrothermally exploded powderspray (ELTEPS) technique.
First, the electrical characteristics of the ELTEPS system were determined. The starting powder of the coatings was titanium
powder mixed with boron carbide powder. This powder was prepared for production of Ti-B-C composite coatings on substrates
using the ELTEPS technique. The coatings obtained were composed of titanium carbide and titanium diboride. The thickness of
the coating obtained by onefold spray was not uniform. The coating obtained by the twofold spray covered the substrate. The
coating obtained by threefold spray was still more precise. The thickness of the coating obtained by threefold spray was about
50 μm and its hardness value was about 30.7±4.5 GPa. 相似文献
6.
大气等离子喷涂锆酸镧热障涂层 总被引:2,自引:0,他引:2
利用自制的稀土元素复合掺杂锆酸镧热喷涂粉末,采用大气等离子喷涂技术,在镍基高温合金表面制备La1.6Nd0.4Ce1.0Zr1.0O7(LNCZ)热障涂层,研究了喷涂参数对涂层沉积率、显微结构、结合强度及抗热震性能的影响。结果表明,增大喷涂功率,降低送粉速率可以有效地提高涂层的沉积率,但对涂层结合和抗热震性能不利。减小喷涂距离不仅提高沉积率,还有利于获得孔径细小、孔隙率适中的层状组织结构,该结构对提高涂层的抗热震性能极为有利。采用DH-1080大气等离子喷涂设备制备LNCZ涂层较好的喷涂条件为:功率40 kW,喷涂距离9 cm,送粉速率12 g/min。 相似文献
7.
Residual stress buildup in thick thermal spray coatings is a property of concern. The adhesion of these coatings to the substrate is influenced by residual stresses that are generated during the coating deposition process. In the HVOF spray process, significant peening stresses are generated during the impact of semimolten particles on the substrate. The combination of these peening stresses together with quenching and thermal mismatch stresses that arise after deposition can be of significant importance. Both numerical method, i.e., Finite Element Method (FEM), and experimental methods, i.e., the Modified Layer Removal Method (MLRM) and Neutron Diffraction, to calculate peening and quenching stresses have been utilized in this work. The investigation was performed on thick Inconel 718 coatings on Inconel 718 substrates. Combined, these numerical and experimental techniques yield a deeper understanding of residual stress formation in the HVOF process and thus a tool for process optimization. The relationship between the stress state and deposit/substrate thickness ratio is given particular interest. 相似文献
8.
The study aimed at characterizing mechanical properties of TiO2 coatings obtained by the use of aqueous suspensions of fine rutile and anatase particles onto metal substrates. Thickness of the coatings was found with the use of optical microscope observations of metallographical cross-sections. The coatings morphology was found with scanning electron microscope (SEM) and their phase composition was determined by X-ray diffraction method. The mechanical properties were characterized using scratch test. The test enabled to characterize the adhesion of coatings by determination of critical force necessary to peel off the coatings from the substrate and, on the other hand, to estimate their cohesion by the measurement of the scratch hardness. The hardness was calculated using the width of the scratch and the value of force applied. The design of experiments (DOE) of spraying with the use of a 23 full factorial plan was applied to rutile powder. The coatings were sprayed onto aluminium substrate. The DOE enabled to find the effects of three principal parameters, i.e. electric power input to plasma, spray distance and suspension feed rate onto coating adhesion expressed by critical force. A preliminary data for anatase powder sprayed with one set of operational parameters onto stainless steel substrate are also shown. 相似文献
9.
Tabbetha A. Dobbins Richard Knight Merrilea J. Mayo 《Journal of Thermal Spray Technology》2003,12(2):214-225
High velocity oxy-fuel (HVOF) thermal spray has been successfully used to deposit yttria-stabilized zirconia (YSZ) for thermal
barrier coating (TBC) applications. Adherent coatings were obtained within a limited range of spray conditions using hydrogen
as fuel gas. Spray parameters such as hydrogen-to-oxygen ratio, spray distance, and substrate cooling were investigated. Spray
distance was found to have a pronounced effect on coating quality; adherent coatings were obtained for spray distances between
75 and 125 mm from the gun exit for the hydrogen-to-oxygen ratios explored. Compared to air plasma spray (APS) deposited YSZ
coatings, the HVOF deposited coatings were more fully stabilized in the tetragonal phase, and of similar density, surface
roughness, and cross-sectional microhardness. Notably, fracture surfaces of the HVOF coatings revealed a more homogeneous
structure. Many theoretical models predict that it should not be possible to melt YSZ in an HVOF flame, and therefore it should
not be possible to deposit viable YSZ coatings by this process. The experimental results in the present work clearly contradict
those expectations. The present results can be explained by taking into account the effect of partial melting and sintering
on particle cohesion, as follows. Combustion chamber pressures (P
o) of ∼3.9 bar (58.8 psi) realized during HVOF gun operation allows adiabatic flame temperature values that are above the zirconia
melting temperature. Under these conditions, the Ranz-Marshall heat transfer model predicts HVOF sprayed particle surface
temperatures T
p that are high enough for partial melting of small (∼10 μm) zirconia particles, T
p=(1.10−0.95)T
m. Further analysis shows that for larger particles (38 μm), adherent coatings are produced when the particle temperature,
T
p=0.59−0.60 T
m, suggesting that sintering may have a role in zirconia particle deposition during HVOF spray. These results suggest two different
bonding mechanisms for powders having a broad particle size distribution. 相似文献
10.
Residual stresses play an important role in the formation and performance of thermal spray coatings. A curvature-based approach where the substrate–coating system deflection and temperature are monitored throughout the coating deposition process was used to determine residual stress formation during cold spray deposition of Al, Cu and Ti coatings. The effect of substrate material (carbon steel, stainless steel and aluminium) and substrate pre-treatment (normal grit blasting, grit blasting with the cold spray system and grinding for carbon steel substrate) were studied for all coating materials with optimized deposition parameters. Mainly compressive stresses were expected because of the nature of cold spraying, but also neutral as well as tensile stresses were formed for studied coatings. The magnitudes of the residual stresses were mainly dependent on the substrate/coating material combination, but the surface preparation was also found to have an effect on the final stress stage of the coating. 相似文献
11.
Nanocrystalline Al−Mg coatings were produced using the cold gas dynamic-spraying technique. Unsieved Al−Mg powder of average
nanocrystalline grain size in the range of 10 to 30 nm and with a particle size distribution from 10 to >100 μm was used as
the feedstock powder. The resulting coatings were evaluated using scanning electron microscopy (SEM), transmission electron
microscopy, as well as microhardness and nanoindentation measurements. Coating observations suggest that the wide particle
size distribution of the feedstock powder has a detrimental effect on the coating quality but that it can be successfully
mitigated by optimizing the spraying parameters. Nanohardness values close to 3.6 GPa were observed in both the feedstock
powder and coatings, suggesting the absence of cold-working hardening effects during the process. The effects of the substrate
surface roughness and thickness on coating quality were investigated. The deposited mass measurements performed on the coatings
showed that the effect of using different grit sizes for the substrate preparation is limited to small changes in the deposition
efficiency of only the first few layers of deposited material. The SEM observation showed that the substrate surface roughness
has no significant effect on the macrostructures and microstructures of the coating. The ability to use the cold gas dynamic
spraying process to produce coatings on thin parts without noticeable substrate damage and with the same quality as coatings
produced on thicker substrates was demonstrated in this work.
The original version of this paper was published in the CD ROM Thermal Spray Connects: Explore Its Surfacing Potential, International Thermal Spray Conference, sponsored by DVS, ASM International, and IIW International Institute of Welding,
Basel, Switzerland, May 2–4, 2005, DVS-Verlag GmbH, Düsseldorf, Germany. 相似文献
12.
Richard R. Chromik Dina Goldbaum Stephen Yue Jean-Gabriel Legoux 《Surface & coatings technology》2010,205(5):1409-1414
A modified ball bond shear test was developed to measure the adhesion of cold sprayed splats to both bulk substrates and cold sprayed coatings. The technique was applied to the deposition of Ti feedstock powder (spherical morphology, 29 μm average dia.) onto a commercially pure bulk Ti plate and onto Ti coatings prepared with the same feedstock powder. Both an adhesion strength and adhesion energy were measured, with trends in adhesion examined as a function of in-air particle velocities between 580 and 825 m/s. Comparisons between cold spray splat on bulk materials versus coatings were conducted for two deposition conditions (694 and 825 m/s). Generally, the adhesion for splats deposited at the higher deposition condition were insensitive to the substrate material, while splats deposited at the lower deposition condition adhered better to the bulk material than to the coatings. 相似文献
13.
E. F. Rybicki J. R. Shadley Y. Xiong DJ. Greving 《Journal of Thermal Spray Technology》1995,4(4):377-383
Young’s modulus and Poisson’s ratio for thermal spray coatings are needed to evaluate properties and characteristics of thermal
spray coatings such as residual stresses, fracture toughness, and fatigue crack growth rates. It is difficult to evaluate
Young’s modulus and Poisson’s ratio of thermal spray coatings be-cause coatings are usually thin and attached to a thicker
and much stiffer substrate. Under loading, the substrate restricts the coating from deforming. Since coatings are used while
bonded to a substrate, it is desirable to have a procedure to evaluate Young’s modulus and Poisson’s ratio in situ.
The cantilever beam method to evaluate the Young’s modulus and Poisson’s ratio of thermal spray coat-ings is presented. The
method uses strain gages located on the coating and substrate surfaces. A series of increasing loads is applied to the end
of the cantilever beam. The moment at the gaged section is calcu-lated. Using a laminated plate bending theory, the Young’s
modulus and Poisson’s ratio are inferred based on a least squares fit of the equilibrium equations. The method is verified
by comparing predicted values of Young’s modulus and Poisson’s ratio with reference values from a three-dimensional finite
ele-ment analysis of the thermal spray coated cantilever beam. The sensitivity of the method is examined with respect to the
accuracy of measured quantities such as strain gage readings, specimen dimensions, ap-plied bending moment, and substrate
mechanical properties. The method is applied to evaluate the Young’s modulus and Poisson’s ratio of four thermal spray coatings
of industrial importance. 相似文献
14.
The Effect of Deposition Conditions on Adhesion Strength of Ti and Ti6Al4V Cold Spray Splats 总被引:1,自引:0,他引:1
Dina Goldbaum J. Michael Shockley Richard R. Chromik Ahmad Rezaeian Stephen Yue Jean-Gabriel Legoux Eric Irissou 《Journal of Thermal Spray Technology》2012,21(2):288-303
Cold spray is a complex process where many parameters have to be considered in order to achieve optimized material deposition
and properties. In the cold spray process, deposition velocity influences the degree of material deformation and material
adhesion. While most materials can be easily deposited at relatively low deposition velocity (<700 m/s), this is not the case
for high yield strength materials like Ti and its alloys. In the present study, we evaluate the effects of deposition velocity,
powder size, particle position in the gas jet, gas temperature, and substrate temperature on the adhesion strength of cold
spayed Ti and Ti6Al4V splats. A micromechanical test technique was used to shear individual splats of Ti or Ti6Al4V and measure
their adhesion strength. The splats were deposited onto Ti or Ti6Al4V substrates over a range of deposition conditions with
either nitrogen or helium as the propelling gas. The splat adhesion testing coupled with microstructural characterization
was used to define the strength, the type and the continuity of the bonded interface between splat and substrate material.
The results demonstrated that optimization of spray conditions makes it possible to obtain splats with continuous bonding
along the splat/substrate interface and measured adhesion strengths approaching the shear strength of bulk material. The parameters
shown to improve the splat adhesion included the increase of the splat deposition velocity well above the critical deposition
velocity of the tested material, increase in the temperature of both powder and the substrate material, decrease in the powder
size, and optimization of the flow dynamics for the cold spray gun nozzle. Through comparisons to the literature, the adhesion
strength of Ti splats measured with the splat adhesion technique correlated well with the cohesion strength of Ti coatings
deposited under similar conditions and measured with tubular coating tensile (TCT) test. 相似文献
15.
Qiang Wang Kevin Spencer Nick Birbilis Ming-Xing Zhang 《Surface & coatings technology》2010,205(1):50-4671
Al-Al2O3 composite coatings were produced on AZ91D magnesium alloy substrates using kinetic metallization (KM), which is a special type of cold spray using a convergent barrel nozzle to attain sonic velocity. The effect of the volume fraction of Al2O3 particles and KM spray temperatures on the microstructure, hardness of the composite coatings, the deposition efficiency, and the bond strength between the coating and substrate was studied. Results show that addition of Al2O3 particles not only significantly improves the density of the coating, but also enhances the deposition efficiency to an optimum value. The bond strength of the composite coatings with the substrate was found to be much stronger than the coating itself, measured using a specially designed lug shear method. Furthermore, based on bond strength data and SEM analysis, higher Al2O3 content resulted in a failure mode transition from adhesive failure to cohesive failure. This is considered a result of a competition between the strengthening of the ceramic reinforcing particles at the coating/substrate interface, and the weakening of coating cohesive strength due to an increase in the proportion of weaker Al-Al2O3 bonds compared with stronger Al-Al bonds. Characterisation of the composite coating in terms of hardness, porosity and microstructure was also conducted. 相似文献
16.
T. Varis J. Knuuttila E. Turunen J. Leivo J. Silvonen M. Oksa 《Journal of Thermal Spray Technology》2007,16(4):524-532
The potential of the high-velocity oxy-fuel (HVOF) thermal spray process for reduced porosity in coatings compared to those
produced by other ambient thermal spray processes is well known. The ability to produce high-density ceramic coatings offers
potential in high-performance applications in the field of wear, corrosion resistance, and dielectric coatings. However, due
to operational limit of the HVOF process to effectively melt the ceramic particles, the process—structure relationship must
be well optimized. It has been also demonstrated that benefits from HVOF ceramic coatings can be obtained only if particles
are melted enough and good lamella adhesion is produced. One strategy to improve melting of ceramic particles in relative
low-flame temperatures of HVOF process is to modify particle crystal structure and composition. In this paper the effect of
the powder manufacturing method and the composition on deposition efficiency of spray process as well as on the mechanical
properties of the HVOF sprayed are studied. Effect of fuel gas, hydrogen vs. propane, was also demonstrated. Studied materials
were alumina-, chromia-, and titania-based agglomerated powders. Coating properties such as microstructure, hardness, abrasive
wear resistance, and relative fracture toughness were compared to the coating manufactured by using conventional fused and
crushed powders. It can be concluded that powder size distribution and microstructure should be optimized to fulfill process
requirements very carefully to produce coatings with high deposition efficiency, dense structure, improved fracture toughness,
and adhesion. 相似文献
17.
Tailoring powder characteristics to suit the plasma spray process can alleviate difficulties associated with the preparation
of hydroxyapatite (HA) coatings. Commercial HA feedstock normally exhibit an angular morphology and a wide particle size range
that present difficulties in powder transport from the powder hopper to the plasma spray gun and in nonuniform melting of
the powders in the plasma flame. Hence, combustion flame spheroidized hydroxyapatite (SHA) was used as the feedstock for plasma
spraying. Spherical particles within a narrow particle size range are found to be more effective for the plasma spray processes.
Results show coatings generated from spheroidized HA powders have unique surface and microstructure characteristics. Scanning
electron microscope (SEM) observation of the coating surface revealed well-formed splats that spread and flatten into disc
configurations with no disintegration, reflecting adequate melting of the HA in the plasma and subsequent deposition consistency.
The surface topography is generally flat with good overlapping of subsequent spreading droplets. Porosity in the form of macropores
is substantially reduced. The cross-section microstructure reveals a dense coating comprised of randomly stacked lamellae.
The tensile bond strengths of the SHA coatings, phase composition, and characteristics of the coatings generated with different
particle sizes (125 to 75 μm, 45 to 75 μm, 20 to 45 μm, and 5 to 20 μm) showed that a high bond strength of ∼16 MPa can be
obtained with SHA in the size range from 20 to 45 μm. This can be improved further by a postspray treatment by hot isostatic
pressing (HIP). However, larger particle size ranges exhibited higher degrees of crystallinity and relatively higher HA content
among the various calcium phosphate phases found in the coatings. 相似文献
18.
Coatings of a composite material consisting of an Al-12Si matrix reinforced with 20 wt.% B4C particles were produced using Cold Gas Dynamic Spray (CGDS) and Pulsed Gas Dynamic Spray (PGDS) processes onto Al-6061 and SS-316L substrates. Two types of composite feedstock powders (mechanically mixed and cryomilled) were used. The influence of the coating process as well as the nature of the feedstock material on the coating microstructure and mechanical properties was studied. The combination of cryomilling to synthesize the feedstock powder and the spray processes provides a unique opportunity to produce hard and dense composite coatings with good cohesion between the deformed particles and good adhesion to the substrate, no phase degradation, very low compressive stresses and high dry sliding wear resistance. The two spray processes have shown almost similar results regarding microstructure and mechanical properties. No effect of the substrate material, Al-6061 and SS-316L, on the coating microstructure and properties was observed. 相似文献
19.
Down-selection and optimization of thermal-sprayed coatings for aluminum mould tool protection and upgrade 总被引:1,自引:0,他引:1
This article details the down-selection procedure for thermally sprayed coatings for aluminum injection mould tooling. A down-selection
metric was used to rank a wide range of coatings. A range of high-velocity oxyfuel (HVOF) and atmospheric plasma spray (APS)
systems was used to identify the optimal coating-process-system combinations. Three coatings were identified as suitable for
further study; two CrC NiCr materials and one Fe Ni Cr alloy. No APS-deposited coatings were suitable for the intended application
due to poor substrate adhesion (SA) and very high surface roughness (SR). The DJ2700 deposited coating properties were inferior
to the coatings deposited using other HVOF systems and thus a Taguchi L18 five parameter, three-level optimization was used
to optimize SA of CRC-1 and FE-1. Significant mean increases in bond strength were achieved (147±30% for FE-1 [58±4 MPa] and
12±1% for CRC-1 [67±5 MPa]). An analysis of variance (ANOVA) indicated that the coating bond strengths were primarily dependent
on powder flow rate and propane gas flow rate, and also secondarily dependent on spray distance. The optimal deposition parameters
identified were: (CRC-1/FE-1) O2 264/264 standard liters per minute (SLPM); C3H8 62/73 SLPM; air 332/311 SLPM; feed rate 30/28 g/min; and spray distance 150/206 mm. 相似文献
20.
This research delivers a generic understanding of the design and integrated performance of the coating-substrate systems under
impact loading, and comprehends the understanding of underpinning failure mechanisms. Repeated severe impacts to the coatings
often result in poor performance by cracking and delamination from the coating-substrate interface. The durability of coatings
thus depends on the choice of coating and substrate materials, coating deposition process, and service conditions. The design
of thermal spray coatings thus requires an optimization of these parameters. This investigation provides insight into the
role of coating and substrate properties on the impact resistance of coated materials, and maps the relationship between the
impact resistance of WC cermet coatings on a variety of substrates. Results indicate that the delamination resistance of the
coating during impact loading not only depends upon the hardness and roughness of the substrate material, but, more importantly,
substrates with a higher work-hardening coefficient indicate a higher delamination resistance.
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