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1.
Dominique Poirier Jean-Gabriel Legoux Rogerio S. Lima 《Journal of Thermal Spray Technology》2013,22(2-3):280-289
Chromium carbide-based thermally sprayed coatings are widely used for high temperature wear applications (typical temperature range from 540 to 900 °C). In these extreme environments at those temperatures, several phenomena will degrade, oxidize, and change the microstructure of the coatings, thereby affecting their wear behavior. Although it can be easily conceived that the Cr3C2-NiCr coating microstructure evolution after high temperature exposure will depend on the as-sprayed microstructure and spraying parameters, very little has been done in this regard. This study intends to develop a better understanding of the effect of spraying parameters on the resulting chromium carbide coating microstructure after high temperature operation and high temperature sliding wear properties. The microstructures of different coatings produced from two morphologies of Cr3C2-NiCr powders and under a window of in-flight particle temperature and velocity values were characterized through x-ray diffraction and scanning electron microscopy. Sliding wear at 800 °C was performed and the wear behavior correlated with the spraying parameters and coating microstructure. Vickers microhardness (300 gf) of the coatings before and after sliding wear was also measured. 相似文献
2.
Guan-Jun Yang Chang-Jiu Li Shi-Jun Zhang Cheng-Xin Li 《Journal of Thermal Spray Technology》2008,17(5-6):782-787
The comparison of the high-temperature erosion behavior of a High-velocity oxyfuel (HVOF) sprayed Cr3C2-NiCr coating with mild steel for circulating fluidized bed boiler tubes was investigated. Results showed that the erosion rate of the mild steel at 800 °C was four times that at 300 °C at an erosion angle of 30°. However, the erosion rate of the HVOF sprayed Cr3C2-NiCr coating was not influenced by the temperature in the range of 300-800 °C. It was found that the erosion resistance of HVOF sprayed Cr3C2-NiCr coating was more than three times higher than that of the mild steel at 700-800 °C. In addition to the ploughing on the coating surface, the cracking along splat interfaces in the coating was clearly observed on the cross-sectional microstructure. The results indicate that the erosion performance of the HVOF sprayed Cr3C2-NiCr coating is controlled by the cohesion between splats and can be further enhanced by improving splat cohesion. 相似文献
3.
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
4.
A selection of WC-Co and Cr3C2-25%NiCr coatings produced by plasma spray and high velocity oxygen fuel (HVOF) deposition techniques were subjected to various
wear tests designed to simulate abrasion, cavitation, sliding, and particle erosion type wear mechanisms. All of the coatings
were at least 200 μm thick and were deposited onto stainless steel substrates. In Part 1 of this contribution, the microstructures
of the coatings were characterized and their mechanical properties were assessed using microindentation procedures. In this
second part of the article, the behavior of the coatings when subjected to the various wear tests is reported and the utility
of microhardness testing as an indication of relative wear resistance is discussed. It is shown that correctly performed,
appropriate microhardness measurements are a good indication of abrasion resistance and sliding wear resistance, and also
correlate well with cavitation resistance in Cr3C2-NiCr. The measurements were less useful for predicting erosion resistance for both Cr3C2-NiCr and WC-Co, however, and for abrasion resistance when WC-Co was ground against SiC. Here the contribution of micromechanisms
involving fracturing and brittle failure is greater than that indicated by the coating microhardness, which is essentially
a measurement of resistance to plastic deformation under equilibrium conditions. 相似文献
5.
Cr3C2-NiCr, NiCr, WC-Co and Stellite-6 alloy coatings were sprayed on ASTM SA213-T11 steel using the HVOF process. Liquid petroleum
gas was used as the fuel gas. Hot corrosion studies were conducted on the uncoated as well as HVOF sprayed specimens after
exposure to molten salt at 900 °C under cyclic conditions. The thermo-gravimetric technique was used to establish the kinetics
of corrosion. XRD, SEM/EDAX and EPMA techniques were used to analyze the corrosion products. All these overlay coatings showed
a better resistance to hot corrosion as compared to that of uncoated steel. NiCr Coating was found to be most protective followed
by the Cr3C2-NiCr coating. WC-Co coating was least effective to protect the substrate steel. It is concluded that the formation of Cr2O3, NiO, NiCr2O4, and CoO in the coatings may contribute to the development of a better hot-corrosion resistance. The uncoated steel suffered
corrosion in the form of intense spalling and peeling of the scale, which may be due to the formation of unprotective Fe2O3 oxide scale. 相似文献
6.
Lingzhong Du Chuanbing HuangWeigang Zhang Tiegang LiWei Liu 《Surface & coatings technology》2011,205(12):3722-3728
NiCr clad hexagonal BN powder (NiCr/hBN) was added to NiCr/Cr3C2 feedstock to improve the tribological properties of chromium carbide nichrome coating. The microstructure, flowability and apparent density of the composite powder, as well as the structure and mechanical properties of the plasma sprayed coating were characterized. The friction and wear behavior of the NiCr/Cr3C2-NiCr/hBN coating from ambient temperature up to 800 °C was evaluated on a ball-on-disk wear tester and compared with that of NiCr/Cr3C2 coating and NiCr/Cr3C2-NiCr/BaF2·CaF2 coating. The results show that NiCr cladding can reduce the decarburization of Cr3C2 and oxidation of hBN during the thermal spray. The main wear mechanisms of the NiCr/Cr3C2-NiCr/hBN composite coating are ploughing and adhesive wear. Layered hexagonal BN particle reduce the direct contact and severe adhesion between friction pairs, thus decreasing the friction coefficient. The NiCr/Cr3C2-NiCr/hBN composite coating shows a promising application in the high temperature environment with the request of both wear resistance and friction reduction. 相似文献
7.
Mahantayya Mathapati Mrityunjay Doddamani M. R. Ramesh 《Journal of Materials Engineering and Performance》2018,27(4):1592-1600
This research examines the deposition of Cr3C2-NiCr/cenosphere and Cr3C2-NiCr coatings on MDN 321 steel through the process of plasma spray. In this process, the solid particle erosion test is established at 200, 400, 600 °C with 30° and 90° impact angles. Alumina erodent is adopted to investigate the erosive behavior of the coating at higher temperatures. The properties of the Cr3C2-NiCr/cenosphere coating are established based on the microhardness, the adhesive strength, the fracture toughness, and the ductility. To quantify volume loss as a result of erosion, an optical profilometer is used. At higher temperature, decrease in the erosion volume loss of Cr3C2-NiCr/cenosphere and Cr3C2-NiCr coatings is observed. The erosion-resistive property of Cr3C2-NiCr/cenosphere coating is higher than that of MDN 321 steel by 76%. This property is influenced by high-temperature stability of mullite, alumina, and protective oxide layer that is formed at elevated temperatures. The morphology of eroded coating discloses a brittle mode of material removal. 相似文献
8.
Lutz-Michael Berger Sabine Saaro Tobias Naumann Michaela Kašparova František Zahálka 《Journal of Thermal Spray Technology》2008,17(3):395-403
The composition WC-(W,Cr)2C-Ni is one of the standard compositions used for the preparation of thermally sprayed coatings by high velocity oxy-fuel
(HVOF) spraying. Surprisingly, this composition has been poorly investigated in the past. Frequent use of commercial designations
WC-‘CrC’-Ni, WC-Cr3C2-Ni, and WC-NiCr indicates the insufficient knowledge about the phase compositions of these powders and coatings. The properties
of these coatings differ significantly from those of WC-Co and WC-CoCr coatings. In this paper, the results of different series
of experiments conducted on HVOF-sprayed WC-(W,Cr)2C-Ni coatings are compiled and their specific benefits pointed out. The focus of this study is on the analysis of the microstructures
and phase compositions of the feedstock powders and coatings. Unlike WC-Co and Cr3C2-NiCr, WC-(W,Cr)2C-Ni is not a simple binary hard phase—binder metal composite. The phase (W,Cr)2C with unknown physical and mechanical properties appears as a second hard phase, which is inhomogeneously distributed in
the feedstock powders and coatings. As examples of coating properties, the oxidation resistance and dry sliding wear properties
are compared with those of WC-10%Co-4%Cr coatings. 相似文献
9.
Erosion Performance of HVOF-Sprayed Cr3C2-NiCr Coatings 总被引:1,自引:0,他引:1
Gang-Chang Ji Chang-Jiu Li Yu-Yue Wang Wen-Ya Li 《Journal of Thermal Spray Technology》2007,16(4):557-565
Cr3C2-NiCr coatings were deposited by high-velocity oxygen fuel (HVOF) spraying process under spray conditions of different flows
of oxygen and propane gases, and spray distances. The orthogonal regression experimental design method was used for systematic
investigation of the influence of spray parameters on the erosion performance of Cr3C2-NiCr coatings. Erosion tests were performed at different jet angles of abrasive particles. The erosion mechanism of Cr3C2-NiCr coatings was examined through the surface morphology and cross-sectional microstructure of the eroded coatings. The
correlations of the carbide particle size and carbide content with the erosion rate were examined. It was found that the erosion
occurred dominantly by spalling of splats from the lamellar interfaces. The spalling resulted from the propagation of cracks
parallel to the interfaces between the lamellae exposed to the surface and underlying coating. The carbide particle size and
content in the coating influenced significantly the erosion performance of Cr3C2-NiCr coatings. 相似文献
10.
Influence of the Spray Angle on the Characteristics of Atmospheric Plasma Sprayed Hard Material Based Coatings 总被引:1,自引:0,他引:1
Wolfgang Tillmann Evelina Vogli Benjamin Krebs 《Journal of Thermal Spray Technology》2008,17(5-6):948-955
This paper presents an investigation of the influence of the spray angle on thermally sprayed coatings. Spray beads were manufactured with different spray angles between 90 and 20° by means of atmospheric plasma spraying (APS) on heat-treated mild steel (1.0503). WC-12Co and Cr3C2-10(Ni20Cr) powders were employed as feedstock materials. Every spray bead was characterized by a Gaussian fit. This opens the opportunity to analyze the influence of the spray angle on coating properties. Furthermore, metallographic studies of the surface roughness, porosity, hardness, and morphology were carried out and the deposition efficiency as well as the tensile strength was measured. The thermally sprayed coatings show a clear dependence on the spray angle. A decrease in spray angle changes the thickness, width, and form of the spray beads. The coatings become rougher and their quality decreases. 相似文献
11.
T. S. Sidhu S. Prakash R. D. Agrawal 《Journal of Materials Engineering and Performance》2006,15(1):122-129
This article demonstrates the successful formulation of NiCrBSi, Cr3C2-NiCr, Ni-20Cr, and Stellite-6 coatings on an Fe-based superalloy by a high-velocity oxyfuel (HVOF) process for hot corrosion
applications. The microstructure, porosity, coating thickness, phase formation, and microhardness properties of the coatings
have been characterized using the combined techniques of optical microscopy, x-ray diffraction, scanning electron microscopy/energy-dispersive
x-ray analysis. A microhardness tester was used to determine the hardness of the coatings. The coatings in general exhibit
characteristic splat-like, layered morphologies due to the deposition and resolidification of successive molten or semimolten
powder particles. The NiCrBSi, Cr3C2-NiCr, and Ni-20Cr coatings have shown a nickel-base face-centered cubic (fcc) structure as a principal phase, whereas Stellite-6
coating has an fcc Co-rich metallic matrix. Oxides/spinel oxides are formed in small fraction as intersplat lamellae or globules
oriented parallel to the substrate surface. Coatings possess some unmelted/partially melted particles, inclusions, and porosity
less than 2%. The microhardness of the coatings is found to be higher than the superalloys. The Cr3C2-NiCr coating has indicated a maximum microhardness of 990 Hv, while a Ni-20Cr coating has shown a minimum value of about
600 Hv. This article is focused on the characterization of HVOF coatings. The hot corrosion behavior of these coatings in
a molten salt (Na2SO4-60%V2O5) environment at 900 °C under cyclic conditions is being presented as part II included in this issue. 相似文献
12.
Zichun Zhao Hui Li Tianlong Yang Hongbin Zhu 《Journal of Thermal Spray Technology》2018,27(4):718-726
Boride materials have drawn great attention in surface engineering field, owing to their high hardness and good wear resistance. In our previous work, a plasma-sprayed TiB2-based cermet coating was deposited, but the coating toughness was significantly influenced by the formation of a brittle ternary phase (Ni20Ti3B6) derived from the reaction between TiB2 and metal binder. In order to suppress such a reaction occurred in the high-temperature spraying process, the high-velocity oxygen-fuel spraying technique was applied to prepare the TiB2-NiCr coating. Emphasis was paid on the microstructure, the mechanical properties, and the sliding wearing performance of the coating. The result showed that the HVOF-sprayed coating mainly consisted of hard ceramic particles including TiB2, CrB, and the binder phase. No evidence of Ni20Ti3B6 phase was found in the coating. The mechanical properties of HVOF-sprayed TiB2-NiCr coating were comparable to the conventional Cr3C2-NiCr coating. The frictional coefficient of the TiB2-NiCr coating was lower than the Cr3C2-NiCr coating when sliding against a bearing steel ball. 相似文献
13.
Thermally sprayed carbide-based coatings are nowadays extensively considered as an alternative to electrolytic hard chrome (EHC) coatings to reduce the environmental impact and the overall cost associated with EHC process. In this investigation, high-velocity oxy-fuel (HVOF) spray process was employed to prepare coatings using the traditional carbide powders namely the WC-10Co4Cr, the Cr3C2-25NiCr and a new type of mixed carbide powder WC-40Cr3C2-25NiCr. The Powder deposition rate, basic mechanical properties, abrasive wear, slurry erosion and corrosion resistance of the three coatings were then compared with the EHC coating. The results show that WC-10Co4Cr coating exhibited the highest hardness, abrasive wear and slurry erosion resistance followed by WC-40Cr3C2-25NiCr, EHC, and Cr3C2-25NiCr coating. The deposition efficiency of the powders as per hierarchy was found to be WC-40Cr3C2-25NiCr > WC-10Co4Cr > Cr3C2-25NiCr and all the HVOF sprayed coatings exhibited higher corrosion resistance than EHC coating. The highest powder deposition efficiency coupled with low density, acceptable tribo-corrosion performance, as well as low post processing cost makes the HVOF sprayed WC-40Cr3C2-25NiCr coating a potential candidate to replace the EHC coating. 相似文献
14.
The role of microstructure in the high temperature oxidation mechanism of Cr3C2-NiCr composite coatings 总被引:1,自引:0,他引:1
Composites of Cr3C2-NiCr provide superior oxidation resistance to WC-Co composites, which has seen them applied extensively to components subjected to combined high temperature erosion and oxidation. This work characterises the variation in oxidation mechanism of thermally sprayed Cr3C2-NiCr composites at 700 °C and 850 °C as a function of heat treatment. Carbide dissolution during spraying increased the Ni alloy Cr concentration, minimising the formation of Ni oxides during oxidation. Compressive growth stresses resulted in ballooning of the oxide over the carbide grains. Carbide nucleation with heat treatment reduced the Ni alloy Cr concentration. The oxidation mechanism of the composite coating changed from being Cr based to that observed for NiCr alloys. 相似文献
15.
Jianhong He Michael Ice Julie M. Schoenung Enrique J. Lavernia Dong H. Shin 《Journal of Thermal Spray Technology》2001,10(2):293-300
The thermal stability behavior of nanostructured Cr3C2-NiCr coatings was investigated. The nanostructured Cr3C2-NiCr coatings, synthesized using mechanical milling and high-velocity oxygen fuel (HVOF) thermal spraying, were thermally
exposed in air at 473, 673, 873, and 1073 K for 8 h. The results show that microhardness of the conventional coating increased
slightly with increasing temperature, while that of the nanostructured coating drastically increased from 1020 to 1240 HV300 for the same temperature increases. Heat treatment led to increases in scratch resistance and decreases in the coefficient
of friction for the nanostructured Cr3C2-NiCr coatings. A high density of Cr2O3 oxide particles with average size of 8.3 nm was found in the nanostructured coatings exposed to high temperatures, which
is thought to be responsible for the observed increase in microhardness and scratch resistance and the decrease in the coefficient
of friction of the nanostructured coatings. 相似文献
16.
Cr3C2-NiCr thermal spray coatings are extensively used to mitigate high temperature erosive wear in fluidised bed combustors and power generation/transport turbines. The aim of this work was to characterise the variation in oxide erosion response as a function of the Cr3C2-NiCr coating microstructure. Erosion was carried out at 700 °C and 800 °C with erodent impact velocities of 225-235 m/s. The erosion behaviour of the oxide scales formed on these coatings, was influenced by the coating microstructure and erosion temperature. Development of the carbide microstructure with extended heat treatment lead to variations in the erosion-corrosion response of the Cr3C2-NiCr coatings. 相似文献
17.
Ji?í Nohava Petr Hau?ild ?árka Houdková Radek En?l 《Journal of Thermal Spray Technology》2012,21(3-4):651-658
This paper compares the results of two approaches of instrumented indentation for characterization of mechanical properties of HVOF coatings. Three types of HVOF sprayed coatings (Cr3C2-NiCr, WC-Co, (Ti, Mo)(C,N)-NiCo) were investigated by the means of isolated nanoindentation and grid indentation methods. The results of the isolated indentation revealed hardness and elastic modulus of the individual phases in very good agreement with the corresponding bulk material. The grid indentation method, based on statistical evaluation of a large number of indentations, was influenced by the carbide-matrix interface, which gave rise to a third peak apart from the two peaks corresponding to the carbides and metallic matrix. As a consequence, the bimodal Gaussian fit was insufficient and a trimodal fit had to be used. The results extracted from low load grid nanoindentations were quite close to the results of isolated indentations whereas higher load grid nanoindentation revealed overall properties of the coating. 相似文献
18.
Lutz-Michael Berger Sabine Saaro Michaela Kašparova 《Surface & coatings technology》2010,205(4):1080-94
The composition WC-(W,Cr)2C-Ni (commercial designations WC-‘CrC’-Ni, WC-Cr3C2-Ni and WC-NiCr) is unique among the WC-based materials used for the preparation of thermally sprayed hardmetal coatings. These coatings show a significantly higher oxidation resistance and high-temperature sliding wear resistance than WC-Co and WC-CoCr coatings do. Unlike WC-Co and Cr3C2-NiCr, WC-(W,Cr)2C-Ni is not a simple binary hard phase-binder metal composite as it is composed of two hard phases: WC and (W,Cr)2C. Surprisingly this composition has been poorly investigated in the past.In this paper coating microstructures and properties obtained from five commercial feedstock powders of different origins using two different liquid-fuelled high velocity oxy-fuel (HVOF) systems (K2 and JP-5000) were investigated. Additional experiments were performed with one powder using atmospheric and vacuum plasma spraying (APS and VPS, respectively). The microstructures and phase compositions of the powders and the coatings were studied. Focus was on the appearance, composition and distribution of the (W,Cr)2C phase which might form or might change its Cr/W ratio during the spray process. The composition of the (W,Cr)2C phase was estimated from the lattice parameters. Hardness HV0.3 was measured for all coatings. The density, Young's modulus and abrasion wear resistance of HVOF-sprayed coatings were studied. 相似文献
19.
WC-Co and Cr<Subscript>3</Subscript>C<Subscript>2</Subscript>-NiCr Coatings in Low- and High-Stress Abrasive Conditions 总被引:1,自引:0,他引:1
Michaela Kašparová František Zahálka Šárka Houdková 《Journal of Thermal Spray Technology》2011,20(3):412-424
The article deals with the evaluation of abrasive wear resistance and adhesive strength of thermally sprayed coatings. The
main attention was paid to differences between low- and high-stress abrasive conditions of the measuring. Conclusions include
the evaluation of specific properties of the WC-Co and the Cr3C2-NiCr High Velocity Oxygen Fuel coatings and the evaluation of the changes in the behavior of the abrasive media. Mainly,
the relationship between the low- and high-stress abrasion conditions and the wear mechanism in the tested materials was described.
For the wear test, the abrasive media of Al2O3 and SiO2 sands were chosen. During wear tests, the volume loss of the tested materials and the surface roughness of the wear tracks
were measured. The wear tracks on the tested materials and abrasive sands’ morphologies were observed using Scanning Electron
Microscopy. It was found that high-stress abrasive conditions change the coatings’ behavior very significantly, particularly
that of the Cr3C2-NiCr coating. Adhesive-cohesive properties of the coatings and relationships among individual structure particles were evaluated
using tensile testing. It was found that the weak bond strength among the individual splats, structure particles, and phases
plays a role in the poor wear resistance of the coatings. 相似文献
20.
The structure, hardness, and shear adhesion strength have been investigated for Cr3C2-NiCr cermet coatings sprayed onto a mild steel substrate by 200 kW high power plasma spraying (HPS) and high velocity oxy-fuel
(HVOF) processes. Amorphous and supersaturated nickel phases form in both as-sprayed coatings. The hardness of the HVOF coating
is higher than that of the HPS coating, because the HVOF coating contains more nonmelted Cr3C2 carbide particles. On heat treating at 873 K, the amorphous phase decomposes and the supersaturated nickel phase precipitates
Cr3C2 carbides so that the hardness increases in the HPS coating.
The hardness measured under a great load exhibits lower values compared with that measured with a small load because of cracks
generated from the indentation. The ratio of the hardnesses measured with different loads can be regarded as an index indicating
the coating ductility. The ductility of the HVOF coating is higher than that of the HPS coating. Adhesion strength of the
HVOF coating was high compared with the HPS coating. The adhesion of the coatings is enhanced by heat treating at 1073 K,
and that of the HVOF coating is over 350 MPa. 相似文献