共查询到20条相似文献,搜索用时 31 毫秒
1.
E. Sánchez E. Bannier V. Cantavella M.D. Salvador E. Klyatskina J. Morgiel J. Grzonka A.R. Boccaccini 《Journal of Thermal Spray Technology》2008,17(3):329-337
Al2O3-13%TiO2 coatings were deposited on stainless steel substrates from conventional and nanostructured powders using atmospheric plasma
spraying (APS). A complete characterization of the feedstock confirmed its nanostructured nature. Coating microstructures
and phase compositions were characterized using SEM, TEM, and XRD techniques. The microstructure comprised two clearly differentiated
regions. One region, completely fused, consisted mainly of nanometer-sized grains of γ-Al2O3 with dissolved Ti+4. The other region, partly fused, retained the microstructure of the starting powder and was principally made up of submicrometer-sized
grains of α-Al2O3, as confirmed by TEM. Coating microhardness as well as tribological behavior were determined. Vickers microhardness values
of conventional coatings were in average slightly lower than the values for nanostructured coating. The wear resistance of
conventional coatings was shown to be lower than that of nanostructured coatings as a consequence of Ti segregation. A correlation
between the final properties, the coating microstructure, and the feedstock characteristics is given. 相似文献
2.
Fabrication and Properties of Plasma-Sprayed Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/ZrO<Subscript>2</Subscript> Composite Coatings 总被引:1,自引:0,他引:1
N. Dejang A. Limpichaipanit A. Watcharapasorn S. Wirojanupatump P. Niranatlumpong S. Jiansirisomboon 《Journal of Thermal Spray Technology》2011,20(6):1259-1268
Al2O3
/xZrO2 (where x = 0, 3, 13, and 20 wt.%) composite coatings were deposited onto mild steel substrates by atmospheric plasma spraying of mixed
α-Al2O3 and nano-sized monoclinic-ZrO2 powders. Microstructural investigation showed that the coatings comprised well-separated Al2O3 and ZrO2 lamellae, pores, and partially molten particles. The coating comprised mainly of metastable γ-Al2O3 and tetragonal-ZrO2 with trace of original α-Al2O3 and monoclinic-ZrO2 phases. The effect of ZrO2 addition on the properties of coatings were investigated in terms of microhardness, fracture toughness, and wear behavior.
It was found that ZrO2 improved the fracture toughness, reduced friction coefficient, and wear rate of the coatings. 相似文献
3.
The Effect of Heat Treatment on the Oxidation Behavior of HVOF and VPS CoNiCrAlY Coatings 总被引:1,自引:0,他引:1
Free-standing VPS and HVOF CoNiCrAlY coatings were produced. The as-sprayed HVOF coating retained the γ/β microstructure of
the feedstock powder, and the VPS coating consisted of a single (γ) phase. A 3-h, 1100 °C heat treatment in vacuum converted
the single-phase VPS coating to a two-phase γ/β microstructure and coarsened the γ/β microstructure of the HVOF coating. Oxidation
of free-standing as-sprayed and heat-treated coatings of each type was carried out in air at 1100 °C for a duration of 100 h.
Parabolic rate constant(s), K
p, were determined for free-standing, as-sprayed VPS and HVOF coatings as well as for free-standing coatings that were heat
treated prior to oxidation. The observed increase in K
p following heat treatment is attributed to a sintering effect eliminating porosity from the coating during heat treatment.
The lower K
p values determined for both HVOF coatings compared to the VPS coatings is attributed to the presence of oxides in the HVOF
coatings, which act as the barrier to diffusion. Oxidation of the as-sprayed coatings produced a dual-layer oxide consisting
of an inner α-Al2O3 layer and outer spinel layer. Oxidation of the heat-treated samples resulted in a single-layer oxide, α-Al2O3. The formation of a thin α-Al2O3 layer during heat treatment appeared to prevent nucleation and growth of spinel oxides during subsequent oxidation. 相似文献
4.
Microstructural characterization of radio frequency and direct current plasma-sprayed Al2O3 coatings
Microstructures of radio frequency (RF) and direct current (DC) plasma-sprayed Al2O3 coatings deposited onto steel substrates were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD),
electron microprobe analysis (EMPA), polarizing optical microscopy (OM), and transmission electron microscopy (TEM). Because
RF and DC plasmas produce different particle heating and acceleration, the morphology, phase structure, and fracture modes
of the coatings vary substantially. In the case of RF coatings, a clear lamellar microstructure with relatively thick lamellae
was observed, which is due to the large particles and the low particle velocities, with α-Al2O3 as the predominant phase and with delamination type of fracture detected on the fracture surface. In contrast, the DC coatings
consisted of predominantly metastable γ-Al2O3 as well as amorphous phases, with a mixed fracture mode of the coating observed. In spite of limited interfacial interdiffusion
detected by EMPA, TEM showed an interfacial layer existing at the interface between the coating and the substrate for both
cases. For RF coatings, the interfacial layer on the order of 1 μm was composed of three sublayers, each of which was different
in composition and morphology. However, the interfacial layer for the DC coating consisted primarily of an amorphous phase,
containing both coating and substrate materials with or without platelike microcrystals; although in some regions a thick
amorphous Al2O3 layer was in direct contact with the substrate. 相似文献
5.
Characterization of plasma sprayed Fe-17Cr-38Mo-4C amorphous coatings crystallizing at extremely high temperature 总被引:5,自引:0,他引:5
A Fe-17Cr-38Mo-4C alloy powder was plasma sprayed by three processes: an 80 kW low-pressure plasma spray (LPPS), a 250 kW
high-energy plasma spray (HPS), and a 40 kW conventional plasma spray (APS). The as-sprayed coating obtained by the LPPS process
is composed of only amorphous phase. As-sprayed coatings obtained by the HPS and APS processes are a mixture of amorphous
and crystalline phases. The three as-sprayed coatings exhibit a high hardness of 1000 to 1100 DPN. The amorphous phase in
these coatings crystallizes at a high temperature of about 920 K. A very fine structure composed of hard ϰ-phase and carbides
is formed after crystallization. The hardness of the coating obtained by LPPS reaches a maximum of 1450 DPN just after crystallization
on tempering and retains a high hardness more than 1300 DPN after tempering at high temperatures of 1173 or 1273 K. The corrosion
potential of the amorphous coating is the highest among the three coatings and higher than that of a SUS316L stainless steel
coating. The anodic polarization measurements infer that the corrosion resistance of the amorphous coating is superior or
comparable to SUS316L stainless steel coating in H2SO4 solution. 相似文献
6.
Ni-Al-SiC powder mixture containing 12 wt.% SiC was prepared by conventional ball milling. Morphological and microstructural
investigations showed that powder particles after 15 h of milling time had the optimum characteristics with respect to their
size and microstructure. X-ray diffraction patterns of powder particles included only the elemental Ni, Al, and SiC peaks
without any traces of oxides or intermetallic phases. The powder mixture was then deposited onto a steel substrate by atmospheric
plasma spray (APS) process under different conditions. The results showed that under APS conditions used here, the coatings
were composed of various intermetallics including Ni-Al and Ni2Al3. The mean hardness of coating was found to be about 567 HV. It was also found that by increasing current density of APS,
the coating/substrate adhesive strength was increased. 相似文献
7.
Emine Bakan Diana Marcano Dapeng Zhou Yoo Jung Sohn Georg Mauer Robert Vaßen 《Journal of Thermal Spray Technology》2017,26(6):1011-1024
Dense, crack-free, uniform, and well-adhered environmental barrier coatings (EBCs) are required to enhance the environmental durability of silicon (Si)-based ceramic matrix composites in high pressure, high gas velocity combustion atmospheres. This paper represents an assessment of different thermal spray techniques for the deposition of Yb2Si2O7 EBCs. The Yb2Si2O7 coatings were deposited by means of atmospheric plasma spraying (APS), high-velocity oxygen fuel spraying (HVOF), suspension plasma spraying (SPS), and very low-pressure plasma spraying (VLPPS) techniques. The initial feedstock, as well as the deposited coatings, were characterized and compared in terms of their phase composition. The as-sprayed amorphous content, microstructure, and porosity of the coatings were further analyzed. Based on this preliminary investigation, the HVOF process stood out from the other techniques as it enabled the production of vertical crack-free coatings with higher crystallinity in comparison with the APS and SPS techniques in atmospheric conditions. Nevertheless, VLPPS was found to be the preferred process for the deposition of Yb2Si2O7 coatings with desired characteristics in a controlled-atmosphere chamber. 相似文献
8.
Plasma-sprayed nanostructured Al2O3/TiO2 powders and coatings 总被引:1,自引:0,他引:1
B. H. Kear Z. Kalman R. K. Sadangi G. Skandan J. Colaizzi W. E. Mayo 《Journal of Thermal Spray Technology》2000,9(4):483-487
Air plasma spray has been used to produce metastable oxide-ceramic powders and coatings, starting with commercially available
Al2O3/13TiO2 powder feed. The feed material undergoes rapid melting and homogenization in the high-temperature zone of the plasma jet.
A metastablex-Al2O3·TiO2 phase is formed when the molten droplets are quenched on a chilled substrate. The metastable phase has a defect spinel structure
and a nanocrystalline grain size. When heated, it decomposes into an equilibrium two-phase structure, consisting ofα-Al2O3 andβ-Al2O3·TiO2. Both types of ceramic materials have potential as hard, wear-resistant coatings. 相似文献
9.
B. Liang G. Zhang H. L. Liao C. Coddet C. X. Ding 《Journal of Thermal Spray Technology》2010,19(6):1163-1170
In this study, nanostructured ZrO2-3 mol% Y2O3 coatings were deposited by air plasma spray using reconstituted feedstock. The coating structures were characterized by x-ray
diffractometer, micro-Raman spectrometer, field emission scanning electron microscope, and transmission electron microscope.
It is revealed that the as-sprayed coating is mainly composed of columnar grains with diameters <100 nm and demonstrates the
better toughness, higher microhardness, and lower porosity. It consists only of nontransformable tetragonal ZrO2 phase. The tribological performance of the coating was examined with a ball-on-disk apparatus under dry sliding conditions.
The results show that the friction coefficient of as-sprayed coating was approximately one-fifth of the conventional zirconia
coating and wear rate was lower one order of magnitude than the conventional zirconia coating. The dominant wear mechanism
is abrasive wear. The improved wear resistance can be attributed to the increased mechanical properties of as-sprayed coating. 相似文献
10.
Xuemei Song Ziwei Liu Mingguang Kong Yongzhe Wang Liping Huang Xuebin Zheng Yi Zeng 《Journal of Thermal Spray Technology》2016,25(4):770-777
The microstructures of three atmospheric plasma-sprayed (APS) Al2O3-ZrO2 coatings were investigated using x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The differences in the microstructures of the three Al2O3-ZrO2 coatings, including their phase compositions, cracks, pores, grain sizes, and solid solutions, were analyzed in detail. A close relationship was observed between the thermal conductivities of the coatings and the microstructures, and the Al2O3-YSZ coatings with more spherical pores, fewer vertical cracks, and finer grains exhibited the lowest thermal conductivity of 0.91 W/m·K. Compared with YSZ coatings, Al2O3-YSZ coatings can exhibit lower thermal conductivity, which may be attributed to the formation of an amorphous phase, smaller grains, and Al2O3-YSZ solid solution. 相似文献
11.
Yaran Niu Zhong Wang Jun Zhao Xuebin Zheng Yi Zeng Chuanxian Ding 《Journal of Thermal Spray Technology》2017,26(1-2):100-107
In this work, ZrB2-20 vol.% MoSi2 (denoted as ZM) composite coatings were fabricated by atmospheric plasma spray (APS) and vacuum plasma spray (VPS) techniques, respectively. Phase composition and microstructure of the composite coatings were characterized. Their oxidation behaviors and microstructure changes at 1500 °C were comparatively investigated. The results showed that VPS-ZM coating was composed of hexagonal ZrB2, tetragonal and hexagonal MoSi2, while certain amount of ZrO2 existed in APS-ZM coating. The oxide content, surface roughness and porosity of VPS-ZM coating were apparently lower than those of APS-ZM coating. The mass gain of APS-ZM coating was maximum at the beginning (1500 °C, 0 h) and then decreased with the oxidation time extending, while the mass of VPS-ZM coating gradually increased with increasing the oxidation time. The possible reasons for the different oxidation behaviors of the two kinds of coatings were analyzed. 相似文献
12.
Mechanical and Thermal Transport Properties of Suspension Thermal-Sprayed Alumina-Zirconia Composite Coatings 总被引:1,自引:1,他引:0
Jörg Oberste Berghaus Jean-Gabriel Legoux Christian Moreau Fariba Tarasi Tomas Chráska 《Journal of Thermal Spray Technology》2008,17(1):91-104
Micro-laminates and nanocomposites of Al2O3 and ZrO2 can potentially exhibit higher hardness and fracture toughness and lower thermal conductivity than alumina or zirconia alone.
The potential of these improvements for abrasion protection and thermal barrier coatings is generating considerable interest
in developing techniques for producing these functional coatings with optimized microstructures. Al2O3-ZrO2 composite coatings were deposited by suspension thermal spraying (APS and HVOF) of submicron feedstock powders. The liquid
carrier employed in this approach allows for controlled injection of much finer particles than in conventional thermal spraying,
leading to unique and novel fine-scaled microstructures. The suspensions were injected internally using a Mettech Axial III
plasma torch and a Sulzer-Metco DJ-2700 HVOF gun. The different spray processes induced a variety of structures ranging from
finely segregated ceramic laminates to highly alloyed amorphous composites. Mechanisms leading to these structures are related
to the feedstock size and in-flight particle states upon their impact. Mechanical and thermal transport properties of the
coatings were compared. Compositionally segregated crystalline coatings, obtained by plasma spraying, showed the highest hardness
of up to 1125 VHN3 N, as well as the highest abrasion wear resistance (following ASTM G65). The HVOF coating exhibited the highest erosion wear
resistance (following ASTM G75), which was related to the toughening effect of small dispersed zirconia particles in the alumina-zirconia-alloyed
matrix. This microstructure also exhibited the lowest thermal diffusivity, which is explained by the amorphous phase content
and limited particle bonding, generating local thermal resistances within the structure. 相似文献
13.
W. Z. Sun J. G. Cheng Z. K. Huang Y. Jiang L. E. Wu L. M. Liu 《Journal of Phase Equilibria and Diffusion》2017,38(1):30-36
The present work determined the phase relations in Si-Al-M-O-C (M = Zr, Mg) systems, involving SiC-Al2O3-ZrO2, SiC-Al2O3-MgO, SiC-SiO2-Al2O3-ZrO2 and SiC-SiO2-Al2O3-MgO systems by XRD phase analyses of the solid-state reacted samples from powder mixtures of SiC, Al2O3, ZrO2, MgO and SiO2. Within these systems, SiC was respectively compatible with other neighboring phases, forming a set of four-phase compatibility tetrahedrons. The subsolidus phase diagrams of the SiC-SiO2-Al2O3-ZrO2 and SiC-SiO2-Al2O3-MgO quaternary systems were presented. 相似文献
14.
Consolidation of Al2O3/Al Nanocomposite Powder by Cold Spray 总被引:1,自引:0,他引:1
Dominique Poirier Jean-Gabriel Legoux Robin A. L. Drew Raynald Gauvin 《Journal of Thermal Spray Technology》2011,20(1-2):275-284
While the improvement in mechanical properties of nanocomposites makes them attractive materials for structural applications, their processing still presents significant challenges. In this article, cold spray was used to consolidate milled Al and Al2O3/Al nanocomposite powders as well as the initial unmilled and unreinforced Al powder. The microstructure and nanohardness of the feedstock powders as well as those of the resulting coatings were compared. The results show that the large increase in hardness of the Al powder after mechanical milling is preserved after cold spraying. Good quality coating with low porosity is obtained from milled Al. However, the addition of Al2O3 to the Al powder during milling decreases the powder and coating nanohardness. This lower hardness is attributed to non-optimized milling parameters leading to cracked particles with insufficient Al2O3 embedding in Al. The coating produced from the milled Al2O3/Al mixture also showed lower particle cohesion and higher amount of porosity. 相似文献
15.
Mohammed Shahien Motohiro Yamada Toshiaki Yasui Masahiro Fukumoto 《Journal of Thermal Spray Technology》2013,22(8):1283-1293
Reactive plasma spraying (RPS) is a promising technology for in situ formation of aluminum nitride (AlN) coatings. Recently, AlN-based coatings were fabricated by RPS of alumina (Al2O3) powder in N2/H2 thermal plasma. This study investigated the feasibility of RPS of a fine Al2O3/AlN mixture and the influence of the plasma gases (N2, H2) on the nitriding conversion, and coating microstructure and properties. Thick AlN/Al2O3 coatings with high nitride content were successfully fabricated. The coatings consist of h-AlN, c-AlN, Al5O6N, γ-Al2O3, and a small amount of α-Al2O3. Use of fine particles enhanced the nitriding conversion and the melting tendency by increasing the surface area. Furthermore, the AlN additive improved the AlN content in the coatings. Increasing the N2 gas flow rate improved the nitride content and complete crystal growth to the h-AlN phase, and enhanced the coating thickness. On the other hand, though the H2 gas is required for plasma nitriding of the Al2O3 particles, increasing its flow rate decreased the nitride content and the coating thickness. Remarkable influence of the plasma gases on the coating composition, microstructure, and properties was observed during RPS of the fine particles. 相似文献
16.
Corrosion resistance and wear resistance are the two important parameters for high performance of zinc galvanic coating. In the present work, the improvement of these two characteristics was achieved by the incorporation of Al2O3-ZrO2 mixed oxide composite in the coating. Al2O3-ZrO2 mixed oxide composite was synthesized from ZrOCl2·8H2O. Aluminium rich zinc coatings with high sliding wear resistance was developed from a galvanic bath containing the mixed oxide. Based on the performance of the coating during physicochemical and electrochemical characterization, the concentration of mixed oxide composite in the bath was optimized as 0.50 wt% Al2O3-0.50 wt% ZrO2. While rich in Al-metal content in the coating caused high corrosion resistance, the incorporation of the mixed oxide improved structural characteristics of the coating resulting in high wear resistance also. The coating was nonporous in nature and even the interior layers had high stability. The coatings have potential scope for high industrial utility. 相似文献
17.
In-situ formed γ-Al2O3 nanocrystals repaired and toughened Al2O3 coating prepared by plasma spraying
During process of plasma spraying of alumina with the stable α phase in the as-received powder, metastable γ phase tends to form in the as-deposited coating. In this paper, plasma-sprayed Al2O3 coating was investigated using transmission electron microscopy. In situ formation of γ-Al2O3 nanocrystals was observed in the pre-existing cracks of the as-sprayed Al2O3 coating, which contributes to self-repairing and self-toughening of the Al2O3 coating. Except for the predominant intergranular fracture, the pre-formed γ-Al2O3 nanocrystals would effectively obstruct the crack development in the coating and then the coating fracture toughness is enhanced. 相似文献
18.
Column Formation in Suspension Plasma-Sprayed Coatings and Resultant Thermal Properties 总被引:1,自引:0,他引:1
Kent VanEvery Matthew J. M. Krane Rodney W. Trice Hsin Wang Wallace Porter Matthew Besser Daniel Sordelet Jan Ilavsky Jonathan Almer 《Journal of Thermal Spray Technology》2011,20(4):817-828
The suspension plasma spray (SPS) process was used to produce coatings from yttria-stabilized zirconia (YSZ) powders with
median diameters of 15 μm and 80 nm. The powder-ethanol suspensions made with 15-μm diameter YSZ particles formed coatings
with microstructures typical of the air plasma spray (APS) process, while suspensions made with 80-nm diameter YSZ powder
yielded a coarse columnar microstructure not observed in APS coatings. To explain the formation mechanisms of these different
microstructures, a hypothesis is presented which relates the dependence of YSZ droplet flight paths on droplet diameter to
variations in deposition behavior. The thermal conductivity (k
th) of columnar SPS coatings was measured as a function of temperature in the as-sprayed condition and after a 50 h, 1200 °C
heat treatment. Coatings produced from suspensions containing 80 nm YSZ particles at powder concentrations of 2, 8, and 11 wt.%
exhibited significantly different k
th values. These differences are connected to microstructural variations between the SPS coatings produced by the three suspension
formulations. Heat treatment increased the k
th of the coatings generated from suspensions containing 2 and 11 wt.% of 80 nm YSZ powder, but this k
th increase was less than has been observed in APS coatings. 相似文献
19.
Kai Yang Jingwei Feng Jian Rong Chenguang Liu Shunyan Tao Chuanxian Ding 《Journal of Thermal Spray Technology》2016,25(3):518-525
In the present study, the phase composition and generation mechanism of the nanocrystals located in the microcracks of plasma-sprayed Al2O3 coating were reevaluated. The Al2O3 coatings were investigated using transmission electron microscopy and x-ray diffraction. We supply the detailed explanations to support the new viewpoint that in situ formation of α-Al2O3 nanocrystals in the preexisting microcracks of the as-sprayed Al2O3 coating may be due to the stress-induced phase transformation. Owing to the partially coherent relationship, the phase interfaces between the α-Al2O3 nanocrystals with the preferred orientation and the γ-Al2O3 matrix may possess better bonding strength. The α-Al2O3 nanocrystals could repair the microcracks in the coating, which further strengthens grain boundaries. Grain boundary strengthening is beneficial to the coating fracture toughness enhancement. 相似文献
20.
C. Giolli M. Turbil G. Rizzi M. Rosso A. Scrivani 《Journal of Thermal Spray Technology》2009,18(4):652-664
Invar alloy (Fe-36%Ni) is used in industrial applications that require high dimensional stability because of its exceptionally
low thermal expansion coefficient. The purpose of this work is to improve the wear resistance of the molds in the production
of carbon-fiber reinforced plastic (CFRP) components applying thermal spray coatings. Four different kinds of commercial powders
were coated on an Invar substrate: ZrO2-8Y2O3, Al2O3-13TiO2, and Cr2O3 by air plasma spray (APS) and WC-CoCr by high-velocity oxygen fuel (HVOF). Metallographic microscopy observation and scanning
electron microscopic analysis were carried out, microhardness and fracture toughness were evaluated using the microindentation
method. Friction behavior and wear resistance were evaluated with pin-on-disk apparatus. Tungsten carbide coating had the
lowest average coefficient of friction. Cermet and alumina-titania coatings showed the lowest wear mass loss. Among the APS
ceramic coatings, alumina-titania exhibited the best wear behavior and the HVOF cermet coating exhibited the best behavior
among all the coatings. 相似文献