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1.
The aim of this investigation was the development of a new quality of thermally sprayed coatings with high resistance against
wear and corrosion and to evaluate the application potential of nano-sized hard phases in thermally sprayed layers. The newly
developed material consists of a highly corrosion-resistant matrix of stainless steel (even without nickel) combined with
nano-structured hard phases of vanadium nitrides (VN). On the other hand, matrices consisting of cobalt-chromium (CoCr) with
submicron hard phases of tungstencarbides (WC) were investigated with respect to microstructure and wear resistance compared
with conventional ones. 相似文献
2.
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
3.
Three Al2O3-13wt.% TiO2 powders, with the same chemical composition but different Al2O3-TiO2 distribution patterns, are plasma sprayed and the resulting coatings are compared in terms of their phase composition, microstructure, hardness, crack growth resistance, and abrasive wear performance. It is demonstrated that the degree of mixing of the Al2O3 and TiO2 ingredients in the feed powder has immense impact on the phase composition, microstructure, hardness, crack growth resistance, and abrasive wear performance of the coatings. A high degree of mixing of Al2O3 and TiO2 in the powder state results in more uniform microstructure, higher hardness, higher crack growth resistance, and consequently better abrasive wear resistance of the coating. 相似文献
4.
A comparative study of tribological behavior of plasma and D-gun sprayed coatings under different wear modes 总被引:3,自引:0,他引:3
Sundararajan G. Prasad K. U. M. Rao D. S. Joshi S. V. 《Journal of Materials Engineering and Performance》1998,7(3):343-351
In recent years, thermal sprayed protective coatings have gained widespread acceptance for a variety of industrial applications.
A vast majority of these applications involve the use of thermal sprayed coatings to combat wear. While plasma spraying is
the most versatile variant of all the thermal spray processes, the detonation gun (D-gun) coatings have been a novelty until
recently because of their proprietary nature. The present study is aimed at comparing the tribological behavior of coatings
deposited using the two above techniques by focusing on some popular coating materials that are widely adopted for wear resistant
applications, namely, WC-12% Co, A12O3, and Cr3C2-MCr.
To enable a comprehensive comparison of the above indicated thermal spray techniques as well as coating materials, the deposited
coatings were extensively characterized employing microstructural evaluation, microhardness measurements, and XRD analysis
for phase constitution. The behavior of these coatings under different wear modes was also evaluated by determining their
tribological performance when subjected to solid particle erosion tests, rubber wheel sand abrasion tests, and pin-on-disk
sliding wear tests. The results from the above tests are discussed here. It is evident that the D-gun sprayed coatings consistently
exhibit denser microstructures and higher hardness values than their plasma sprayed counterparts. The D-gun coatings are also
found to unfailingly exhibit superior tribological performance superior to the corresponding plasma sprayed coatings in all
wear tests. Among all the coating materials studied, D-gun sprayed WC-12%Co, in general, yields the best performance under
different modes of wear, whereas plasma sprayed Al2O3 shows least wear resistance to every wear mode. 相似文献
5.
6.
The principal aim of this study was to compare the sliding wear performance of as-sprayed and Hot Isostatically Pressed (HIPed)
thermal spray cermet (WC-12Co) coatings. Results indicate that HIPing technique can be successfully applied to post-treat
thermal spray cermet coatings for improved sliding wear performance, not only in terms of coating wear, but also in terms
of the total volume loss for test couples. WC-12Co coatings sprayed by a HVOF system were deposited on SUJ-2 bearing steel
substrate and then encapsulated and HIPed at 850 °C for one hour. A high frequency reciprocating ball on plate rig was used
to measure the sliding wear resistance of these coatings in dry conditions under steel and ceramic contact configurations
at two different loads. Results are discussed in terms of coating microstructure, microhardness, fracture toughness and residual
stress evaluations. Microstructural investigations indicate fundamental changes in grain morphology, whereas x-ray diffraction
revealed beneficial transformations in phase composition of these coatings during the HIPing post treatment. The effects of
these microstructural changes on the physical properties and wear resistance are discussed. 相似文献
7.
In this work, the hot and cold erosive wear mechanisms of HVOF and plasma-sprayed NiCr-based coatings are evaluated. Erosion tests were carried out in specially developed equipment, with possible variations in temperature and attack angle. The effects of erodent incrustation (SEM/EDS mapping) and oxidation of metallic coating (mass weight) were considered. The results were associated with the microstructural characteristics of the coatings (porosity, size of lamellae) and with the mechanical properties, such as microhardness and elasticity modulus. The obtained results showed that NiCr coatings are ductile, a property similar to monolithic metallic materials. The porosity influenced both the amount of incrusted alumina particles and oxidation. The increase in temperature caused higher oxidation and erodent incrustation. 相似文献
8.
Reactive plasma spraying of wear-resistant coatings 总被引:8,自引:0,他引:8
A method for producing wear-resistant, carbide-reinforced coatings has been investigated. A conventional low-pressure plasma
gun has been modified with a downstream reactor into which carbon-containing gases are mixed, heated, and disassociated. The
disassociated gas ions—H* and C* —are subsequently brought into contact with heated, molten metal matrix powders. Experiments
with NiCr/Ti blends and W powders have shown that uniformly dispersed carbides such as, TiC, Cr^Cy, WC, and W2C were formed
in situ on the metal precursor powders during deposition. The in situ formed particles, being formed directly from the matrices,
show excellent matrix cohesion and lead to high and uniform deposit microhardnesses. The process is described and several
evaluations of materials, reactive gases, and spray conditions are reported. Microanalysis of the coatings are presented,
microhardness values are reported, and XRD identifies the in situ formed phases. 相似文献
9.
To find an alternate coating to hard electroplated chrome in internal combustion engines, wear tests and metallurgical characterization
have been performed on plasma-sprayed chromium oxide, metal-arc-sprayed martensitic stainless steel, and electroplated chromium
coatings applied to steel base material. A wear test rig was fabricated that simulated the reciprocating sliding wear under
lubrication encountered in internal combustion engines. The chromium oxide coating was found to perform equally well compared
to the hard chrome coating that is conventionally used. 相似文献
10.
To testify to the advantage of large ceramic powder spraying, numerical simulations and experimental studies on the behavior
of large yttria-stabilized zirconia (YSZ) powder in a high-power hybrid plasma spraying process have been carried out. Numeric
predictions and experimental results showed that, with the high radio frequency (RF) input power of 100 kW, the most refractory
YSZ powder with particle sizes as large as 88 μm could be fully melted and well-flattened splats could be formed. A large
degree of flattening (ξ) of 4.7 has been achieved. The improved adhesive strength between the large splat and the substrate
was confirmed based on the measurement of the crack density inside of the splats. A thick YSZ coating >300 μm was successfully
deposited on a large CoNiCrAlY-coated Inconel substrate (50×50×4 mm in size). The ultradense microstructure without clear
boundaries between the splats and the clean and crack-free interface between the top-coat and the bond-coat also indicate
the good adhesion. These results showed that highpower hybrid plasma spraying of large ceramic powder is a very promising
process for deposition of highquality coatings, especially in the application of thermal barrier coatings (TBCs). 相似文献
11.
为研究铸造碳化钨粉末物性对激光熔覆陶瓷颗粒增强Fe基复合材料耐磨性能的影响,将不同制备方法和粒径的铸造碳化钨粉末添加到Fe基合金粉中,在45号钢表面进行激光熔覆以获得高硬度和高耐磨的合金化层。利用金相显微镜、扫描电子显微镜(SEM)、X射线衍射仪(XRD)、硬度计分别分析了合金化层的显微组织、物相组成以及显微硬度。利用轮式磨损试验机测试了其常温下的耐磨性能,并进行了比较。结果表明:熔覆层主要由莱氏体组成,碳化钨粉末的制备方法和粒径差异对复合材料的耐磨性能具有重要影响。等离子旋转电极雾化法制备的碳化钨粉末能起到最好的增强耐磨作用,粒径细的碳化钨粉末比粒径粗的粉末增强耐磨效果要好。 相似文献
12.
13.
14.
粉末结构对HVOF金属陶瓷涂层腐蚀冲蚀磨损性能的影响 总被引:1,自引:0,他引:1
采用3种不同NiCr粘结相含量和两种不同尺度WC颗粒的金属陶瓷粉末,运用超音速火焰喷涂(HVOF)方法制备了Cr3 C2-NiCr、WC-12%Co涂层,在5%H2 SO4、15%棕刚玉和水混合介质条件下,运用腐蚀冲蚀磨损试验机测定了涂层在45°冲蚀角下的失重量变化规律,研究了喷涂粉末NiCr含量和WC颗粒尺度对所沉积金属陶瓷涂层耐腐蚀冲蚀磨损性能的影响。结果表明,HVOF喷涂Cr3C2-NiCr、WC-12%Co涂层在5%H2SO4、15%棕刚玉和水混合介质条件下的腐蚀冲蚀率均低于低碳钢,并且Cr3 C2-NiCr涂层的抗腐蚀冲蚀性能要优于WC-12%Co涂层。Cr3 C2-40%NiCr和Cr3 C2-25%NiCr涂层其腐蚀冲蚀率低于Cr3 C2-10%NiCr涂层,与纳米尺度WC颗粒相比,微米尺度WC颗粒所制备的WC-12%Co涂层的抗腐蚀冲蚀性能较好。 相似文献
15.
等离子喷涂热障涂层的隔热性分析 总被引:4,自引:0,他引:4
采用大气等离子喷涂方法制备不同类型的氧化钇部分稳定氧化锆热障涂层:传统涂层、纳米团聚粉末制备的纳米涂层和空心球粉末制备的空心球涂层。通过扫描电镜、透射电镜、压汞仪和激光脉冲法观察和测试各种涂层的组织形貌、空隙分布和导热系数,并在相同条件下测试各种涂层的隔热性能。结果表明:纳米涂层空隙率最低,内部孔洞细小。空心球涂层组织相对疏松,内部层片更薄,有最高的空隙率和最大的平均空隙大小。传统涂层介于二者之间。纳米涂层和传统涂层均表现出双态空隙大小分布。涂层的导热系数均随着温度的上升而升高。传统涂层的热导率最高,纳米涂层与空心球涂层的热导率相接近。纳米涂层具有最好的隔热性能,空心球涂层接近纳米涂层的隔热效果。隔热效果与涂层厚度呈线性关系。随着厚度增加,导热系数低的纳米涂层和空心球涂层的隔热效果增长幅度高于传统涂层。 相似文献
16.
A. C. Savarimuthu H. F. Taber I. Megat J. R. Shadley E. F. Rybicki W. C. Cornell W. A. Emery D. A. Somerville J. D. Nuse 《Journal of Thermal Spray Technology》2001,10(3):502-510
Tungsten carbide (WC) thermal spray coatings have gained increased acceptance for commercial aircraft applications driven
by the desire to replace chromium electroplate due to environmental and economic considerations. In order to confidently replace
electroplated chrome with WC thermal spray coatings in aircraft applications, the coatings must demonstrate fatigue and wear
characteristics as good as or better than those of electroplated chrome. Previous research in this area has shown that the
fatigue life of the WC thermal spray coatings can be improved by inducing compressive residual stresses in the coating. This
paper compares the wear characteristics of several types of WC thermal spray coatings with those of electroplated chrome in
sliding wear tests using the “block-on-ring” procedures described in the ASTM G77 standard. Wear results are interpreted in
terms of coating residual stresses and in terms of x-ray diffraction (XRD) and scanning electron microscope (SEM) analyses. 相似文献
17.
Nanostructured WC-12Co coatings were deposited by high velocity oxy-fuel (HVOF) spraying with an agglomerated powder. The effect of flame conditions on the microstructure of the nanostructured coatings was investigated. The wear properties of the coatings were characterized using a dry rubber-wheel wear test. The results show that the nanostructured WC-Co coatings consist of WC, W2C, W and an amorphous binder phase. The microstructure of the coating is significantly influenced by the ratio of oxygen flow to fuel flow. Under the lower ratio of oxygen/fuel flow, the nanostructured coating presents a relative dense microstructure and severe decarburization of WC phase occurs during spraying. With increasing ratio of oxygen/fuel flow, the bonding of WC particles in the coating becomes loose resulting from the original structure of feedstock and the decarburization of WC becomes less owing to limited heating to the powder. Both the decarburization of WC particles in spraying and the bonding among WC particles in the coatings affect the wear performance. The examination of the worn surfaces of the nanostructured coatings reveals that the dominant wear mechanisms would be spalling from the interface of WCCo splats when spray particles undergo a limited melting. While the melting state of the spray particles is improved,the dominant wear mechanisms become the plastic deformation and plowing of the matrix and spalling of WC particles from the matrix. 相似文献
18.
Robert Vaßen Franziska Traeger Detlev Stöver 《Journal of Thermal Spray Technology》2004,13(3):396-404
It is generally known that the porosity of thermal barrier coatings is essential to guarantee a sufficiently high strain tolerance
of the coating during thermal cycling. However, much less is known about the influence of the specific morphology of porosity,
such as microcracks and typically larger pores, on the performance of the coatings. Both features are usually formed during
plasma spraying of yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBCs). In this investigation, the influence
of microcracks on the thermal cycling behavior was studied. The amount of microcracks within YSZ thermal barrier coatings
was changed by changing the powder-feeding rate. Only small changes of the total porosity were observed. Mercury porosimetry
served as a tool to investigate both the amount of microcracks and pores in the coating. Additionally, microcrack densities
were determined from metallographical investigations. A linear dependence between the amount of fine pores determined by Hg
porosimetry and the crack density was obtained for one set of coatings. Thermal cycling TBC specimens with different microcrack
densities were produced and tested in a gas burner test facility. At high surface temperatures (above 1300 °C), failure occurred
in the ceramic close to the surface. Under these conditions, the samples with increased horizontal microcrack densities showed
a significant increase of thermal cycling life. 相似文献
19.
20.
Andreas Wank Bernhard Wielage Hanna Pokhmurska Eduard Friesen Guido Reisel 《Surface & coatings technology》2006,201(5):1975-1980
Electroplated hard chromium and thermal spray hardmetal coatings are widely used in a variety of applications for wear protection of component surfaces. The two protective coating types are tested in direct comparison for tribological conditions of dry abrasive wear (Taber Abraser test) and dry oscillating wear load. Oscillating wear tests are carried out both with hardened 100Cr6 steel and alumina balls as counterbody. Different types of hardmetal coatings are imparted. Besides HVOF sprayed coatings also coatings sprayed by an APS gun with axial powder feed are tested. For HVOF spraying besides standard WC/Co(Cr) feedstock also coarse (d50 = 5 μm) and fine carbide feedstock (d50 = 0.8 μm) and ultrafine powders, i.e. 2 μm < d < 12 μm, are considered. Use of ultrafine powders is particularly interesting from the economical point of view, as belt grinding can be sufficient for finishing in many cases. The optimum coating solution for wear protection depends on the specific tribosystem. The choice of feedstock, spraying process, equipment and processing conditions does not only depend on the resultant tribological properties. Therefore simultaneous influence on corrosion protection capability and thermal conductivity might have to be considered. 相似文献