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1.
The hybrid spray process that combines arc spray with a high-velocity oxyfuel (HVOF)/plasma jet has recently demonstrated
its effectiveness in deposition of functionally gradient coatings. This approach aims at exploiting the combined attributes
of the arc-spray technique and the HVOF/air plasma spraying (APS) technique. This paper presents high-speed visualization
and plume characterization of an arc/HVOF hybrid spray gun as well as a twin-wire arc-spray gun. The physics of atomization
in the hybrid spray process is examined using a high-speed camera. A DPV/CPS-2000 (Tecnar, St-Bruno, QC, Canada) particle
diagnostics sensor is used to measure particle velocity, temperature, size, and distribution. The influence of feed material,
arc parameters, and HVOF parameters on the particle characteristics is presented. Differences in the in-flight characteristics
between the hybrid and the twin-wire arc process are discussed aided by the observed atomization phenomena with the high-speed
camera.
This article was originally published inBuilding on 100 Years of Success, Proceedings of the 2006 International Thermal Spray Conference (Seattle, WA), May 15–18, 2006, B.R. Marple, M.M. Hyland, Y.-Ch. Lau, R.S. Lima, and J. Voyer, Ed., ASM International, Materials
Park, OH, 2006. 相似文献
2.
Fabrication and Characterization of Thermal-Sprayed Fe-Based Amorphous/Nanocrystalline Composite Coatings: An Overview 总被引:2,自引:0,他引:2
Wenmin Guo Yuping Wu Jianfeng Zhang Sheng Hong Gaiye Li Guobing Ying Ji Guo Yujiao Qin 《Journal of Thermal Spray Technology》2014,23(7):1157-1180
This review focuses on the recent development of iron (Fe)-based amorphous/nanocrystalline composite coatings, which have attracted much attention due to their attractive combination of high hardness/strength, elevated abrasive wear resistance, and enhanced corrosion resistance. Accompanying the advancements in various thermal spray technologies, industrial application fields of Fe-based amorphous/nanocrystalline composite coatings are becoming more diverse. In the main part, the typical empirical rules for the design of amorphous alloys with high glass-forming ability are generalized and discussed at first. Then various thermal spray technologies for the fabrication of Fe-based amorphous/nanocrystalline composite coatings, such as high velocity oxygen/air spray (HVOF/HVAF), air plasma spray (APS), low-pressure plasma spray (LPPS), high-energy plasma spray (HPS), and high velocity arc spray (HVAS) processes, are introduced. The microstructures, hardness, wear resistance, and corrosion resistance of Fe-based amorphous/nanocrystalline composite coatings formed using these thermal spray technologies are reviewed and compared. Finally, the existing challenges and future prospects are proposed. 相似文献
3.
Coating deposition on many industrial components with good microstructural, mechanical properties, and better wear resistance is always a challenge for the thermal spray community. A number of thermal spray methods are used to develop such promising coatings for many industrial applications, viz. arc spray, flame spray, plasma, and HVOF. All these processes have their own limitations to achieve porous free, very dense, high-performance wear-resistant coatings. In this work, an attempt has been made to overcome this limitation. Molybdenum coatings were deposited on low-carbon steel substrates using wire–high-velocity oxy-fuel (W-HVOF; WH) thermal spray system (trade name HIJET 9610®). For a comparison, Mo coatings were also fabricated by arc spray, flame spray, plasma spray, and powder-HVOF processes. As-sprayed coatings were analyzed using x-ray diffraction, scanning electron microscopy for phase, and microstructural analysis, respectively. Coating microhardness, surface roughness, and porosity were also measured. Adhesion strength and wear tests were conducted to determine the mechanical and wear properties of the as-sprayed coatings. Results show that the coatings deposited by W-HVOF have better performance in terms of microstructural, mechanical, and wear resistance properties, in comparison with available thermal spray process (flame spray and plasma spray). 相似文献
4.
P. S. Mohanty A. D. Roche R. K. Guduru V. Varadaraajan 《Journal of Thermal Spray Technology》2010,19(1-2):484-494
Oxide dispersion strengthened alloys (ODS), although not commonly used in coating applications, have long been used for high-temperature structural applications due to their superior creep properties. In this paper, we present the design, synthesis, and characterization of a new class of functionally engineered high-temperature coatings in which ultrafine oxide particulates are dispersed in the matrix alloy to achieve superior creep resistance along with improved high-temperature corrosion and erosion resistance. These coatings were fabricated using a novel technique called “hybrid spray process”. Hybrid spray technique combines arc spray and high-velocity oxy fuel (HVOF) spray processes; the metallic matrix alloys are fused by the wire arcing component of the process, whereas the ultrafine particles are synthesized in-flight by the HVOF component from liquid precursors. These particulate dispersed high-temperature composite coatings were fabricated using liquid precursors for SiO2, Cr2O3, Al2O3, and wire feed stock of 55/45 NiCr, in one step. The coatings were then characterized using electron microscopy (SEM/TEM) and thermogravimetric analysis (TGA). High-temperature erosion, oxidation, and corrosion performance of these coatings were also evaluated and compared with 304 stainless steel, arc sprayed NiCr coatings as well as Alloy 625 overlay cladding. The hybrid spray process produced dense coatings with uniform dispersion of the ultrafine oxide particles. Further, these coatings also demonstrated superior corrosion, erosion, and oxidation resistance; SiO2 particulate dispersion being most effective in terms of high-temperature corrosion resistance. 相似文献
5.
Mechanical and thermomechanical properties of metal spray invar for composite forming tooling 总被引:1,自引:0,他引:1
The subject of this paper is the assessment of the thermal and mechanical properties of Invar steel coatings, deposited using
electric arc spraying, and the correlation of these properties to the spray parameters and processes used to offer coatings
with characteristics appropriate to the requirements of tools used in the fabrication of precision polymer matrix composite
work pieces. In particular, two processing methods, inert and air atomization, and three arc spray gun configurations (air
cap design) were evaluated. The low coefficient of thermal expansion (CTE) properties of Invar are maintained in the spray-deposited
coatings using both high velocity oxy-fuel (HVOF) and air-atomized arc spraying, although HVOF coatings have significantly
lower CTE and greater durability than those deposited by arc spraying. The mechanical properties of the coatings are low compared
to bulk Invar, regardless of the spray parameters and hardware used. Inert arc spraying affords more consistent coating characteristics
but this comes with a compromised durability. The spray hardware was found to be more significant in determining the coating
properties than the parameters employed. 相似文献
6.
Characterization of thermal sprayed nanostructured WC-Co coatings derived from nanocrystalline WC-18wt.%Co powders 总被引:3,自引:0,他引:3
Nanostructured WC-Co coatings were synthesized using high velocity oxygen fuel (HVOF) thermal spray. The nanocrystalline feedstock
powder with a nominal composition of WC-18 wt.%Co was prepared using the novel integrated mechanical and thermal activation
(IMTA) process. The effects of HVOF thermal spray conditions and powder characteristics on the microstructure and mechanical
properties of the as-sprayed WC-Co coatings were studied. It was found that the ratio of oxygen-to-hydrogen flow rate (ROHFR)
and the starting powder microstructures had strong effects on decarburization of the nano-coatings. Decarburization was significantly
suppressed at low ROHFR and with the presence of free carbon in the powder. The level of porosity in the coatings was correlated
with the powder microstructure and spray process conditions. The coating sprayed at ROHFR=0.5 exhibited the highest microhardness
value (HV300g=1077), which is comparable to that of conventional coarse-grained coatings. 相似文献
7.
Optimization of Arc-Sprayed Ni-Cr-Ti Coatings for High Temperature Corrosion Applications 总被引:1,自引:0,他引:1
High Cr content Ni-Cr-Ti arc-spray coatings have proven successful in resisting the high temperature sulfidizing conditions found in black liquor recovery boilers in the pulp and paper industry. The corrosion resistance of the coatings is dependent upon the coating composition, to form chromium sulfides and oxides to seal the coating, and on the coating microstructure. Selection of the arc-spray parameters influences the size, temperature and velocity of the molten droplets generated during spraying, which in turn dictates the coating composition and formation of the critical coating microstructural features—splat size, porosity and oxide content. Hence it is critical to optimize the arc-spray parameters in order to maximize the corrosion resistance of the coating. In this work the effect of key spray parameters (current, voltage, spray distance and gas atomizing pressure) on the coating splat thickness, porosity content, oxide content, microhardness, thickness, and surface profile were investigated using a full factorial design of experiment. Based on these results a set of oxidized, porous and optimized coatings were prepared and characterized in detail for follow-up corrosion testing. 相似文献
8.
《Acta Materialia》2007,55(15):5089-5101
The application of thick thermally sprayed coatings on metallic parts has been widely accepted as a solution to improve their corrosion and wear resistance. Key attributes of these coatings, such as adherence to the substrate, are strongly influenced by the residual stresses generated during the coating deposition process. In high-velocity oxy-fuel (HVOF) thermal spraying, due to the relatively low temperature of the particle, significant peening stresses are generated during the impact of molten and semi-molten particles on the substrate. Whilst models exist for residual stress generation in plasma-based thermal spray processes, finite element (FE) prediction of residual stress generation for the HVOF process has not been possible due to the increased complexities associated with modelling the particle impact. A hybrid non-linear explicit–implicit FE methodology is developed here to study the thermomechanical processes associated with particle impingement and layer deposition. Attention is focused on the prediction of residual stresses for an SS 316 HVOF sprayed coating on an SS 316 substrate. 相似文献
9.
Current Status and Future Prospects of Warm Spray Technology 总被引:1,自引:0,他引:1
Seiji Kuroda Makoto Watanabe KeeHyun Kim Hiroshi Katanoda 《Journal of Thermal Spray Technology》2011,20(4):653-676
A modification of high-velocity oxy-fuel (HVOF) thermal spray process named as warm spray (WS) has been developed. By injecting
room temperature inert gas into the combustion gas jet of HVOF, the temperature of the propellant gas can be controlled in
a range approximately from 2300 to 1000 K so that many powder materials can be deposited in thermally softened state at high
impact velocity. In this review, the characteristics of WS process were analyzed by using gas dynamic simulation of the flow
field and heating/acceleration of powder particles in comparison with HVOF, cold spray (CS), and high-velocity air-fuel (HVAF)
spray. Transmission electron microscopy of WS and CS titanium splats revealed marked differences in the microstructures stemming
from the different impact temperatures. Mechanical properties of several metallic coatings formed under different WS and CS
conditions were compared. Characteristics of WC-Co coatings made by WS were demonstrated for wear resistant applications. 相似文献
10.
Effect of high-velocity oxygen-fuel thermal spraying on the physical and mechanical properties of type 316 stainless steel 总被引:1,自引:0,他引:1
T. C. Totemeier 《Journal of Thermal Spray Technology》2005,14(3):369-372
Data on the microstructural, physical, and mechanical characteristics of high-velocity oxygen-fuel (HVOF)-sprayed type 316
stainless steel coatings are presented and compared with properties of wrought 316 stainless steel. Coatings were prepared
at three different spray particle velocities; coating characteristics are presented as a function of velocity. The coatings
had relatively low porosity and oxide contents and were significantly harder than annealed, wrought 316 stainless steel. The
hardness difference is primarily attributed to high dislocation densities resulting from peening imparted by high-velocity
spray particles. The coating hardness increased with increasing spray particle velocity, reflecting increased peening effects.
The elastic modulus of the coatings was essentially identical to wrought material. The mean coefficient of thermal expansion
of as-sprayed coatings was lower than wrought material, but the expansion of annealed coatings matched the wrought behavior. 相似文献
11.
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
12.
High temperature protection requires full coating density, high adhesion, minor oxide inclusions, and preferably fine grains, which is not achievable in most thermal spray processes. High velocity oxygen fuel (HVOF) thermal spray process has been applied extensively for making such coatings with the highest density and adhesion strength, but the existence of not melted or partially melted particles are usually observed in the HVOF coatings because of relatively low flame temperature and short particle resident time in the process. This work has investigated the development of an innovative HVOF process using a liquid state suspension/slurry containing small alloy powders. The advantages of using small particles in a HVOF process include uniform coating, less defective microstructure, higher cohesion and adhesion, full density, lower internal stress, and higher deposition efficiency. Process investigations have proven the benefits of making alloy coatings with full density and high bond strength attributing to increased melting of the small particles and the very high kinetic energy of particles striking on the substrate. High temperature oxidation and hot corrosion tests at 800 °C have demonstrated that the alloy coatings made by novel LS-HVOF process have superior properties to conventional counterpart coatings in terms of oxidation rates and corrosion penetration depths. 相似文献
13.
超音速火焰喷涂纳米结构涂层研究进展 总被引:1,自引:0,他引:1
超音速火焰(High Velocity Oxy -Fuel,简称HVOF)喷涂具有高速和相对较低的温度两个重要特征,能够获得比普通火焰喷涂或等离子喷涂(Plasma Spray,简称PS)结合强度更高的致密涂层.纳米材料具有独特的表面效应、体积效应及量子尺寸效应,其电学、力学、磁学、光学和热学等性能产生了惊人的变化.随着材料科学技术的深入发展, 在实际生产和生活中运用性能优良的纳米材料倍受人们关注,其中,采用热喷涂技术制备纳米结构涂层是构筑纳米结构材料的最具前途的方法之一.从目前国内外的情况来看,HVOF喷涂纳米结构涂层技术的研究取得了较大的进展.综合国内外文献,总结了HVOF喷涂制备纳米结构涂层的研究现状,着重阐述了热喷涂纳米涂层的基本过程和结合机理,指出了利用HVOF喷涂纳米结构涂层存在的问题,并对热喷涂纳米结构涂层的发展前景作了展望. 相似文献
14.
15.
J. Tuominen P. Vuoristo T. Mäntylä M. Kylmälahti J. Vihinen P. H. Andersson 《Journal of Thermal Spray Technology》2000,9(4):513-519
Thermal spray processes are widely used to protect materials and components against wear, corrosion and oxidation. Despite
the use of the latest developments of thermal spraying, such as high-velocity oxy-fuel (HVOF) and plasma spraying, these coatings
may in certain service conditions show inadequate performance,e.g., due to insufficient bond strength and/or mechanical properties and corrosion resistance inferior to those of corresponding
bulk materials. The main cause for a low bond strength in thermalsprayed coatings is the low process temperature, which results
only in mechanical bonding. Mechanical and corrosion properties typically inferior to wrought materials are caused by the
chemical and structural inhomogeneity of the thermal-sprayed coating material. To overcome the drawbacks of sprayed structures
and to markedly improve the coating properties, laser remelting of sprayed coatings was studied in the present work. The coating
material was nickel-based superalloy Inconel 625, which contains chromium and molybdenum as the main alloying agents. The
coating was prepared by HVOF spraying onto mild steel substrates. High-power continuous wave Nd:YAG laser equipped with large
beam optics was used to remelt the HVOF sprayed coating using different levels of power and scanning speed. The coatings as-sprayed
and after laser remelting were characterized by optical microscopy and scanning electron microscopy (SEM). Laser remelting
resulted in homogenization of the sprayed structure. This strongly improved the performance of the laser-remelted coatings
in adhesion, wet corrosion, and high-temperature oxidation testing. The properties of the laser-remelted coatings were compared
directly with the properties of as-sprayed HVOF coatings and with plasma-transferred arc (PTA) overlay coatings and wrought
Inconel 625 alloy. 相似文献
16.
17.
NiCrBSi and Ni-50Cr coatings were deposited using the high velocity oxygen fuel (HVOF) spray process under different spray
parameters with two powders of different sizes to clarify the influence of the melting state of spray particles on the adhesive
strength of the coating. The adhesive strength of the coating was estimated according to the American Society for Testing
and Materials (ASTM) C633-79. The melting state of the spray droplet was examined from the coating microstructure. It was
found that the melting state of spray particles had a significant effect on the adhesive strength of HVOF sprayed Ni-based
coatings. The significant melting of the spray particle did not contribute to the increase in the adhesion of HVOF metallic
coatings. On the other hand, the deposition of a partially melted large particle contributed to the substantial improvement
of adhesive strength of the HVOF coating. The subsequent coating presented a dense microstructure and yielded an adhesive
strength of more than 76 MPa, which was double that of the coating deposited with completely molten particles. It can be suggested
that the good melting of the spray particle is mainly related to the mechanical interlocking effect, which reaches the limited
and approximately defined adhesive strength up to 40–50 MPa. 相似文献
18.
X. Q. Ma J. Roth D. W. Gandy G. J. Frederick 《Journal of Thermal Spray Technology》2006,15(4):670-675
High-velocity oxygen fuel (HVOF) thermal spray processes are used in applications requiring the highest density and adhesion
strength, which are not achievable in most other thermal spray processes. Similar to other thermal spray processes, however,
a normal HVOF process is unable to apply fine powders less than 10 μm via a powder feeder. The advantages of using smaller
and even nanosized particles in a HVOF process include uniform microstructure, higher cohesion and adhesion, full density,
lower internal stress, and higher deposition efficiency. In this work, a new process has been developed for HVOF forming of
fine-grained Inconel 625 alloy layers using a liquid feedstock containing small alloy particles. Process investigations have
shown the benefits of making single and duplex layered coatings with full density and high bond strength, which are attributed
to the very high kinetic energy of particles striking on the substrates and the better melting of the small particles.
This article was originally published inBuilding on 100 Years of Success, Proceedings of the 2006 International Thermal Spray Conference (Seattle, WA), May 15–18, 2006, B.R. Marple, M.M. Hyland, Y.-Ch. Lau, R.S. Lima, and J. Voyer, Ed., ASM International, Materials
Park, OH, 2006. 相似文献
19.
Thermal spray processes such as plasma spraying and HVOF have gained markets due to a steady process of development of materials
and equipment. One disadvantage of thermal spray processes is that costs must be competitive compared to techniques such as
PTA and electroplating. In order to reduce costs, the more economical spray processes like conventional wire flame spraying,
as well as arc spraying, are becoming more popular. There are modern arc spray gun designs on the market that meet the requirements
of modern coating properties, for example aviation overhaul applications as well as the processing of cored wires. Nevertheless,
the physical basis of arc spraying is well known. The aim of the present investigation is to show how the influence of spray
velocity (not particle velocity) affects coating structure with respect to arc spray parameters. 相似文献
20.
High Velocity Oxy-Fuel (HVOF) spray techniques can produce high performance alloy and cermet coatings for applications that require wear resistant surfaces. In HVOF process, the particle velocity and temperature determine the resultant coating properties and in many cases enables a better understanding of the process.The aim of this study is to investigate influences of different oxygen/fuel ratios on velocity and temperature of flying particles as well as properties of the HVOF thermal sprayed WC-CoCr coatings. Particle parameters were recorded just prior to impact on the substrate using in-flight particle diagnostic tool Accuraspray-g3®. Detailed correlation of particle parameters and the coating properties are evaluated in order to deduce particle parameter ranges providing coatings with optimum properties. 相似文献