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1.
Development of WC-Co Coatings Deposited by Warm Spray Process 总被引:1,自引:0,他引:1
Pornthep Chivavibul Makoto Watanabe Seiji Kuroda Jin Kawakita Masayuki Komatsu Kazuto Sato Junya Kitamura 《Journal of Thermal Spray Technology》2008,17(5-6):750-756
The high-velocity oxy-fuel (HVOF) process is commonly used to deposit WC-Co coatings. There are some problems with this process; especially the decomposition and decarburization of WC during spraying make a coating brittle. To suppress such degradation, the warm spray (WS) process was applied to deposit WC-Co coatings, which is capable of controlling the flame temperature in the range of 500-2000 °C. The microstructure and phases of the deposited coatings were characterized by using SEM and XRD, and the mechanical properties such as hardness, fracture toughness, and wear properties were also investigated. WS process successfully suppressed the formation of the detrimental phases such as W2C and W, which are usually observed in HVOF coatings. The WS coatings showed the similar trend of the hardness variation for Co content with a sintered bulk material. Improvement of toughness and wear behavior was also observed in WS coatings. 相似文献
2.
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
3.
Šárka Houdková Michaela Kašparová František Zahálka 《Journal of Thermal Spray Technology》2010,19(5):893-901
The spraying angle is one of the deposition parameters that influence the quality of thermally sprayed coatings. In theory,
decreasing the spraying angle results in lower process deposition efficiency, whereas the porosity of coatings increases,
becoming a cause of poorer microstructure and mechanical properties. In this study, the dependence of microstructure together
with the basic mechanical properties and wear of WC-Co and Cr3C2-NiCr high-velocity oxyfuel (HVOF) sprayed coatings on the spraying angle was investigated. For each coating, the maximum
spraying angle was determined that can be used without significantly decreasing coating quality. Based on the changes in properties
of coatings and requirements for the process deposition efficiency, a maximum 30° diversion from the normal spray direction
is recommended for WC-Co and 15° diversion for Cr3C2-NiCr coatings. 相似文献
4.
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
5.
There has been an increase in interest of late regarding the properties of thermally sprayed WC-Co cermets with nanograin
carbide particles. These powders have shown interesting properties in sintered components, giving high values of hardness
(2200–2300 VHN) and improved wear properties. The method used for the processing for these materials—solution formation, spray
drying and chemical conversion, rather than introduction of WC as solid particles to a molten binder—allows the formation
of sub-100 nm WC particles as a hard second phase.
The work presented here examined the effect of composition on the microstructure and wear properties of some nanostructured
WC-Co materials. WC-Co cermets with 8, 10, 12, and 15% Co binder phase were deposited using a Sulzer Metco hybrid DJ HVOF
thermal spray system. Optimization of deposition conditions was necessary because of the unique morphology of the powders
(thick-shelled hollow spheres) to produce dense consolidated deposits.
There is a higher degree of decarburization of the WC phase in the nanostructured materials compared with the conventional
WC-Co. This dissolution of the hard phase is also noted to increase on decreasing binder phase content.
The nanostructured WC-Co coatings have a lower wear resistance compared with the conventional WC-Co for abrasive wear and
small particle erosion. The abrasive wear resistance of these nanostructured materials was found to increase on decreasing
cobalt binder content. This trend in abrasive wear resistance is consistent with studies on conventional sized cermets and
is believed to be more dependent upon proportion of binder phase content than degree of decarburization for the materials
studied. The small particle erosion resistance of the nanostructured coatings was found to increase on increasing cobalt content. 相似文献
6.
Parameter study of HP/HVOF deposited WC-Co coatings 总被引:3,自引:0,他引:3
H. L. de Villiers Lovelock P. W. Richter J. M. Benson P. M. Young 《Journal of Thermal Spray Technology》1998,7(1):97-107
The deposition parameters of WC-17% Co coatings produced using the JP-5000 liquid-fuel HP/HVOF system (Eutectic TAFA) were
investigated with the initial purpose of parameter improvement and optimization. The coating microstructures, porosities,
phase compositions, and abrasion resistance were characterized. Preliminary work using the Taguchi statistical experimental
design method aimed at optimizing the spray parameters in terms of the microstructure and phase composition was unsuccessful.
The variations in the measured properties were too small to be correlated with the spray parameters. Subsequent experiments
showed this was primarily due to the fact that the properties, particularly the abrasion resistance, of the WC-Co coatings
were not primarily influenced by variations in the spray parameters, but were more dependent on the powder composition, particle
size range, and manufacturing route. Hence, the application of Taguchi techniques would have been more effective over a much
wider parameter space than was originally used. This result is valuable because it suggests that this process is robust and
can be used for WC-Co coatings without large investments in spray parameter optimization and control once the coating and
powder type have been fixed. 相似文献
7.
W. Tillmann I. Baumann P. S. Hollingsworth L. Hagen 《Journal of Thermal Spray Technology》2014,23(1-2):262-280
Fine structured and nanostructured materials represent a promising class of feedstock for future applications, which has also attracted increasing interest in the thermal spray technology. Within the field of wear protection, the application of fine structured or nanostructured WC-Co powders in the High Velocity Oxy-Fuel flame spraying technique (HVOF) provides novel possibilities for the manufacturing of cermet coatings with improved mechanical and tribological characteristics. In this study the tribological behavior of HVOF sprayed coatings derived from conventional, fine and nanostructured WC-12Co powders under sliding and rolling wear are investigated and the results are compared to C45 steel (Mat.-No. 1.0503). In addition, sliding and rolling wear effects on a microscopic level are scrutinized. It has been shown that under optimized spray conditions the corresponding fine and nanostructured WC-12Co coatings are able to obtain higher wear resistances and lower friction coefficients than the conventional coatings. This can be attributed to several scaling effects of the microstructure and to the phase evolution of the coating, which are discussed. 相似文献
8.
High velocity oxygen fuel (HVOF) thermal spray has been widely used to deposit hard composite materials such as WC-Co powders
for wear-resistant applications. Powder morphology varies according to production methods while new powder manufacturing techniques
produce porous powders containing air voids which are not interconnected. The porous microstructure within the powder will
influence in-flight thermal and aerodynamic behavior of particles which is expected to be different from fully solid powder.
This article is devoted to study the heat and momentum transfer in a HVOF sprayed WC-Co particles with different sizes and
porosity levels. The results highlight the importance of thermal gradients inside the particles as a result of microporosity
and how HVOF operating parameters need to be modified considering such temperature gradient. 相似文献
9.
10.
WC-Co coatings are primarily deposited using the high velocity oxy-fuel (HVOF) spray process. However, the decomposition and decarburization of carbides during spraying affects the wear performance and fracture toughness of the coatings. In this paper, a novel high pressure HVOF was developed to achieve lower particle temperature and higher particle velocity. It enables combustion chamber pressures up to 3.0 MPa. The influence of combustion chamber pressure and oxygen/fuel ratio on WC-Co particle velocity and temperature levels were analyzed by numerical simulation. The experimental results show that the combustion chamber pressure and the oxygen/fuel ratio have a significant influence on particle velocity and melting degree, as well as on the microstructure and microhardness of the coating. High velocity WC-Co particles in different states, i.e., molten, semi-molten, and non-molten can be readily obtained by changing the spraying conditions. A comparison to the conventional JP-5000 was also performed. 相似文献
11.
High Velocity Oxy-Fuel (HVOF) has the potential to produce hydroxyapatite (HA; Bio-ceramic) coatings based on its experience with other sprayed ceramic materials. This technique should offer mechanical and biological results comparable to other thermal spraying processes, such as atmospheric plasma thermal spray, currently FDA approved for HA deposition. Deposition of HA via HVOF is a new venture especially using the Sulzer Metco Diamond Jet (DJ) process, and the aim of this article was to establish this technique's potential in providing superior HA coating results compared to the FDA-approved plasma spray technique. In this research, a Design of Experiment (DOE) model was developed to optimize the Sulzer Metco DJ HVOF process for the deposition of HA. In order to select suitable ranges for the production of HA coatings, the parameters were first investigated. Five parameters (factors) were researched over two levels namely: oxygen flow rate, propylene flow rate, air flow rate, spray distance, and powder flow rate. Coating crystallinity and purity were measured at the surface of each sample as the responses to the factors used. The research showed that propylene, air flow rate, spray distance, and powder feed rate had the largest effect on the responses, and the study aimed to find the preferred optimized settings to achieve high crystallinity and purity of percentages of up to 95%. This research found crystallinity and purity values of 93.8 and 99.8%, respectively, for a set of HVOF parameters which showed improvement compared to the crystallinity and purity values of 87.6 and 99.4%, respectively, found using the FDA-approved Sulzer Metco Atmospheric Plasma thermal spray process. Hence, a new technique for HA deposition now exists using the DJ HVOF facility; however, other mechanical and biorelated properties must also be assessed. 相似文献
12.
The mechanical behavior of high-velocity oxyfuel (HVOF) sprayed titania (TiO2) coatings was evaluated using Vickers hardness measurements on the cross section and top surface. The distribution of hardness
values for the cross-section and top surface under 25, 50, 100, 300, 500, and 1000 g loads was analyzed via Weibull statistics.
The coating microstructure was evaluated using scanning electron microscopy (SEM). It was observed that the microstructural
features were similar in the top surface and cross-section, different from the lamellar structure commonly found in thermal
spray coatings. X-ray diffraction (XRD) analysis identified rutile as the major coating phase. The in-flight sprayed particle
parameters such as temperature and velocity were determined using a commercial diagnostic system based on pyrometry and time-of-flight
measurements. The uniformity of the microstructure resulted in a near isotropic behavior of the mechanical properties, such
as hardness, in the coating cross-section and top surface. High Weibull modulus values were observed when compared with results
of other thermal spray coatings available in the literature. These initial results should contribute to a more general understanding
of the conditions necessary to achieve coatings with high uniformity and assist in the engineering of coating microstructures
for specific applications. 相似文献
13.
The high velocity oxy-fuel(HVOF) based thermal spray process has developed as a potential advantageous approach for fabricating various kinds of functional coatings.In this article,the coatings of Mo-based alloy were synthesized using the HVOF process.The microstructure and the mechanical properties of the HVOF-processed coatings were investigated using SEM,TEM,XRD,and hardness and wear tests.Annealing treatment was applied to the as-sprayed coatings to develop the microstructure and its effect on the microstructure and mechanical properties of the coatings was examined.It is found that the HVOF-processed Mo-based alloy coatings are comprised of an amorphous splat matrix embedded with nano-sized crystalline particles.Annealing at temperatures over 950 ℃ results into crystallization of the amorphous matrix.The mechanical properties of the as-sprayed coatings are enhanced with annealing temperature up to 750 ℃ and from 950 to 1050 ℃,keeps constant between 750 and 950 ℃,and reduce over 1050 ℃.The change of the mechanical property with the microstructure was illustrated in the study. 相似文献
14.
S. Thiele L. -M. Berger M. Herrmann M. Nebelung R. B. Heimann T. Schnick B. Wielage P. Vuoristo T. Schnick 《Journal of Thermal Spray Technology》2002,11(2):218-225
The preparation of thermally sprayed, dense, Si3N4-based coatings can be accomplished using composite spray powders with Si3N4 embedded in a complex oxide binder matrix. Powders with excellent processability were developed and produced by agglomeration
(spray drying) and sintering. Optimization of the heat transfer into the powder particles was found to be the most decisive
factor necessary for the production of dense and well-adhering coatings. In the present work, different thermal spray processes
such as detonation gun spraying (DGS), atmospheric plasma spraying (APS) with axial powder injection, and high-velocity oxyfuel
spraying (HVOF) were used. The coatings were characterized using optical and scanning electron microscopy (SEM), x-ray diffraction
(XRD), and microhardness testing. The wear resistance was tested using a rubber wheel abrasion wear test (ASTM G65). In addition,
thermoshock and corrosion resistances were determined. The microstructure and the performance of the best coatings were found
to be sufficient, suggesting the technical applicability of this new type of coating. 相似文献
15.
Elastic modulus measurements via laser-ultrasonic and knoop indentation techniques in thermally sprayed coatings 总被引:1,自引:0,他引:1
R. S. Lima S. E. Kruger G. Lamouche B. R. Marple 《Journal of Thermal Spray Technology》2005,14(1):52-60
Nondestructive techniques for evaluating and characterizing coatings were extensively demanded by the thermal spray community;
nonetheless, few results have been produced in practice due to difficulties in analyzing the complex structure of thermal
spray coatings. Of particular interest is knowledge of the elastic modulus values and Poisson’s ratios, which are very important
when seeking to understand and/or model the mechanical behavior or to develop life prediction models of thermal spray coatings
used in various applications (e.g., wear, fatigue, and high temperatures). In the current study, two techniques, laser-ultrasonics
and Knoop indentation, were used to determine the elastic modulus of thermal spray coatings. Laser-ultrasonics is a noncontact
and nondestructive evaluation method that uses lasers to generate and detect ultrasound. Ultrasonic velocities in a material
are directly related to its elastic modulus value. The Knoop indentation technique, which has been widely used as a method
for determining elastic modulus values, was used to compare and validate the measurements of the laser-ultrasonic technique.
The determination of elastic modulus values via the Knoop indentation technique is based on the measurement of elastic recovery
of the dimensions of the Knoop indentation impression. The approach used in the current study was to focus on evaluating the
elastic modulus of very uniform, dense, and near-isotropic titania and WC-Co thermal spray coatings using these two techniques.
Four different coatings were evaluated: two titania coatings produced by air plasma spray (APS) and high-velocity oxyfuel
(HVOF) and two types of WC-Co coatings, conventional and multimodal (nanostructured and microsized particles), deposited by
HVOF.
The original version of this article was published as part of the ASM Proceedings, Thermal Spray 2003: Advancing the Science and Applying the Technology, International Thermal Spray Conference (Orlando, FL), 5–8 May, 2003, Basil R. Marple and Christian Moreau, Eds., ASM International,
2003. 相似文献
16.
This article reports on a series of experiments with various high-velocity oxygen fuel spray systems (Jet Kote, Top Gun, Diamond
Jet (DJ) Standard, DJ 2600 and 2700, JP-5000, Top Gun-K) using different WC-Co and WC-Co-Cr powders. The microstructure and
phase composition of powders and coatings were analyzed by optical and scanning electron microscopy and x-ray diffraction.
Carbon and oxygen content of the coatings were determined to study the decarburization and oxidation of the material during
the spray process. Coatings were also characterized by their hardness, bond strength, abrasive wear, and corrosion resistance.
The results demonstrate that the powders exhibit various degrees of phase transformation during the spray process depending
on type of powder, spray system, and spray parameters. Within a relatively wide range, the extent of phase transformation
has only little effect on coating properties. Therefore, coatings of high hardness and wear resistance can be produced with
all HVOF spray systems when the proper spray powder and process parameters are chosen.
This paper originally appeared in Thermal Spray: Meeting the Challenges of the 21st Century; Proceedings of the 15th International Thermal Spray Conference, C. Coddet, Ed., ASM International, Materials Park, OH, 1998. This proceedings paper has been extensively reviewed according
to the editorial policy of the Journal of Thermal Spray Technology. 相似文献
17.
M. H. Enayati F. Karimzadeh M. Tavoosi B. Movahedi A. Tahvilian 《Journal of Thermal Spray Technology》2011,20(3):440-446
Nanocrystalline NiAl intermetallic powder was prepared by mechanical alloying (MA) of Ni50Al50 powder mixture and then deposited on low carbon steel substrates by high velocity oxy fuel (HVOF) thermal spray technique
using two sets of spraying parameters. X-ray diffraction (XRD), scanning electron microscopy (SEM), transition electron microscopy
(TEM), differential scanning calorimetry (DSC), and hardness test were used to characterize the prepared powders and coatings.
The MA of Ni50Al50 powder mixture led to the formation of NiAl intermetallic compound. The resulting powder particles were three dimensional
in nature with irregular morphology and a crystallite size of ~10 nm. This powder was thermally sprayed by HVOF technique
to produce coating. The deposited coating had a nanocrystalline structure with low oxide and porosity contents. The hardness
of coatings was in the range of 5.40-6.08 GPa, which is higher than that obtained for NiAl coating deposited using conventional
powders. 相似文献
18.
Nanostructured titania (TiO2) coatings were produced by high-velocity oxyfuel (HVOF) spraying. They were engineered as a possible candidate to replace
hydroxyapatite (HA) coatings produced by thermal spray on implants. The HVOF sprayed nanostructured titania coatings exhibited
mechanical properties, such as hardness and bond strength, much superior to those of HA thermal spray coatings. In addition
to these characteristics, the surface of the nanostructured coatings exhibited regions with nanotextured features originating
from the semimolten nanostructured feedstock particles. It is hypothesized that these regions may enhance osteoblast adhesion
on the coating by creating a better interaction with adhesion proteins, such as fibronectin, which exhibit dimensions in the
order of nanometers. Preliminary osteoblast cell culture demonstrated that this type of HVOF sprayed nanostructured titania
coating supported osteoblast cell growth and did not negatively affect cell viability.
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.
The aim of this experimental study was to ascertain the fatigue failure modes of thermal spray coatings in rolling/sliding
contact. These failure modes outline the design requirements of thermal spray coatings for high-stress tribological applications
including impact and point or line contact loading. Recently, a number of scientific studies have addressed the fatigue performance
and durability of thermal spray coatings in rolling/sliding contact, but investigations on the mechanisms of these failures
are seldom reported. The understanding of such failure mechanisms is, however, critical in optimizing the generic design of
these overlay coatings. This study takes a holistic approach to summarize the results of ongoing research on various cermet
(WC-Co) and ceramic (Al2O3) coatings deposited by detonation gun (D-Gun), high-velocity oxyfuel (HVOF), and high-velocity plasma spraying (HVPS) techniques,
in a range of coating thickness (20–250 μm) on various steel substrates to deliver an overview of the various competing failure
modes. Results indicate four distinct modes of fatigue failure in thermal spray cermet and ceramic coatings: abrasion, delamination,
bulk failure, and spalling. The influences of coating process, thickness, materials, properties of substrate materials, and
prespray conditions on these fatigue failure modes are also discussed. A modified four-ball machine was used to investigate
these failure modes under various tribological conditions of contact stress and lubrication regimes in conventional steel
and hybrid ceramic contact configurations. Results are discussed in terms of pre- and post-test surface examination of rolling
elements using scanning electron microscopy (SEM), electron probe microscopy analysis (EPMA), and surface interferometry,
as well as subsurface observations using x-ray diffraction (XRD), residual stress analysis, and dye-penetrant investigations. 相似文献
20.
Carbide based thermal spray coatings are routinely applied to mitigate erosion under industrial conditions. However, the mechanism of erosion response under aggressive high velocity impact conditions remains unclear. In this work Cr3C2-25%NiCr thermal spray coatings were eroded at an impact velocity of 150 m/s by 20-25 µm alumina grit. Coatings were deposited by High Velocity Air Fuel (HVAF) and High Velocity Oxygen Fuel (HVOF) thermal spray techniques to generate a range of coating quality spanning that applied industrially. In Part 1 of this two-part series, the mechanism of erosion as a function of coating composition and microstructure variation is discussed. The HVOF coating underwent significant in-flight dissolution of the carbide phase. The erosion response of the supersaturated NiCr matrix was characterised by brittle cracking and fracture. The HVAF coating retained a high carbide content with minimal phase dissolution. However, the rapid solidification of the matrix material made the coating prone to brittle interphase cracking during impact. On a larger scale, splat based erosion mechanisms played a significant role, especially in the HVOF coating. The mechanisms of impact response of these coatings were dependent upon the depth of erodent penetration and could not, therefore, be extrapolated from erosion testing at lower velocities. 相似文献