Manufacturing and Macroscopic Properties of Cold Sprayed Cu-In Coating Material for Sputtering Target

This study attempted to manufacture a Cu-In coating layer via the cold spray process and to investigate the applicability of the layer as a sputtering target material. In addition, changes made to the microstructure and properties of the layer due to annealing heat treatment were evaluated, compared, and analyzed. To examine the microstructural and property changes made to the Cu-In coating layer and Cu coating layer (comparison material), ICP, XRD, SEM, and other tests were conducted; purity, density, hardness, porosity, and bond-strength were measured. The results showed that coating layers with thickness of 20 mm (Cu) and 810 μm (Cu-In) could be manufactured via cold spraying under optimal process conditions. With the Cu-In coating layer, the pure Cu and intermetallic compounds of Cu₇In₃ and CuIn₄ were found to exist inside the layer regardless of annealing heat treatment. The preannealing inconsistent microstructure of the layer, whose phases were difficult to distinguish was found to have transformed into one with clearer phase distinction and fine, consistent grains following thermal treatment via a progress of recovery, recrystallization, and grain growth. The porosity and hardness values of the coating layers were 1.4% and 133.9 HV, respectively, for Cu and 3.54% and 476.6 HV, respectively, for Cu-In. The values of the Cu-In layer were higher than those of the Cu layer in terms of porosity and hardness, which declined drastically after annealing. With the porosity of the Cu-In coating layer in particular, the higher value found during the preannealing stage dropped to 0.36% after heat treatment of 773 K/1 h as the level on a par with pure Cu (0.44%), thus indicating the improved quality of the Cu-In layer. Moreover, the results of the bond-strength measurement performed on the Cu-In coating layer and annealing treated materials revealed the strength to be relatively high for heat treated coating layers. Based on the findings of this study and on the comparison and discussion of the properties that are typically required of the target material, the Cu-In coating layer manufactured via cold spray process and annealing heat treatment can be said to be applicable as sputtering target in the future.     

Effect of Cathode Microstructure on Arc Velocity and Erosion Rate of Cold-Sprayed Copper Cathodes in a Magnetically Rotated Atmospheric Pressure Arc

Atmospheric pressure arc velocity and erosion measurements were performed on cold-sprayed cathodes in a continuously running arc system. Ultrahigh purity (99.99% pure) argon was used as plasma forming gas. An external magnetic field of 0.10 T was used to rotate the arc, which was operated at a constant power of 6 kW (40 V). Cathodes having microstructures with mean grain sizes, ranging from 1.12 to 3.06 μm, were produced using cold spraying (CS) and annealing methods. CS cathodes were tested in their as-sprayed state and annealed state. Annealed CS coatings with near equi-axed grains of 2.29 μm average size gave 60% higher steady-state arc velocities and up to 50% lower erosion rates than massive copper cathodes having 20-23 μm average grain size. An effect of cathode microstructure on arc velocity and on arc erosion rates was observed.     

Nanocrystalline copper coatings produced by cold spraying

Copper powder was cryomilled for 12 hours to achieve particle size in the range of 2 μm to 25 μm, which powder was subsequently used as feedstock for the deposition of nanocrystalline (nc) Cu coating via cold spraying. The as-milled copper powder was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The particle size of the cryomilled Cu powder was detected by laser scattering. The microstructure of the coating was analyzed using SEM and scanning transmission electron microscopy (STEM). The XRD and HRTEM analysis showed that the grain size of the cryomilled Cu powder was about 5 to 40 nm. This nanoscale structure was retained after the cold spraying. The nanoindentation analysis showed that the nc Cu coating hardness value reached 3.3 GPa, which was higher than that of its coarse grained counterpart.     

Microstructure evolution of cold-sprayed coating during deposition and through post-spraying heat treatment

The microstructural features of cold-sprayed coatings were investigated using Cu, Ti and Zn feedstocks by optical microscopy, scanning electron microscopy and transmission electron microscopy to reveal the microstructure evolution mechanisms in cold spray. Four typical effects including tamping, refinement, impact-induced fusion and annealing were examined on microstrueture. It is found that the microstructure of cold spray coating is remarkably influenced by spray materials. Ti coatings consist of evident porous layer and Cu coatings present a limited porous layer only near the surface. It is clear that the successive tamping effect and dynamic refinement of grains significantly influence the microstructure evolution of cold-sprayed coating. The tamping effect leads to the densification of porous coating layer gradually and the refinement effect leads to the formation of fine microstructure. It is considered that the large difference in the formation of porous layer is attributed to the dynamic impact pressure and hardenability of materials. It is also found that the impact-induced fusion during deposition of Zn coating can also modify the interfacial microstructure between particles in cold spray coating. Moreover, the nanocrystalline phase can be formed at the interfaces among particles resulting from the localized melting of the interfaces and tamping effect. Furthermore, the annealing treatment can modify the microstructure and property of a cold-sprayed coating.     

Effect of powder alloy composition on the microstructure and properties of kinetic sprayed Cu-Ga based coating materials

This study attempted to manufacture Cu-Ga coating materials via the kinetic spray process and examined the effect of powder alloy composition on the microstructure and properties of the kinetic sprayed Cu-Ga based coating materials. Cu-15 at%Ga, Cu-20 at%Ga, and Cu-30 at%Ga powders were prepared and used. Annealing heat treatments were conducted at 200 °C~800 °C. The results showed that the coating layers could be manufactured with Cu-15 at%Ga and Cu-20 at%Ga powders via the kinetic spray process, except for Cu- 30 at%Ga. A single phase of pure Cu was observed in the Cu-15 at%Ga coating layer and Cu and Cu₃Ga phases in the Cu-20 at%Ga coating layer. A small amount of Ga₂O₃ was also detected between deposited particles in both coating layers. It was difficult to obtain the coating layer due to the shattering of powders during the kinetic spraying with Cu-30 at%Ga powder, which is made up of a variety of inter-metallic compounds. Porosity and hardness decreased as the annealing temperature increased, and porosity decreased into 0.48% (Cu-15 at%Ga), 0.74%(Cu-20 at%Ga) at 800 °C. Annealing heat treatment appeared to be effective in enhancing the density of the coating layers without generating a new phase. This study also considered to suggest the optimal alloy composition of kinetic sprayed Cu-Ga based coating material for sputtering target.     

Deposition effects of WC particle size on cold sprayed WC-Co coatings

The WC particle size and its influence on the deposition of Co-based cermets are examined. Micron and nanostructured powders with similar Co content were employed. Varying the WC particle size influenced significantly the deposition efficiency of the coating process. Micrometer-structured WC-Co feedstocks did not permit coating build up when processed under comparable or elevated thermal spray parameters used for the nanostructured WC-Co feedstocks. In addition, micrometer-structured WC-Co coatings exhibited a conjoint erosion and deposition effect on the surface. Fine WC particles (< 1 μm) were observed near the substrate interface and larger WC particles (1-2 μm) in the vicinity of the coating surface. These observations indicate the existence of a critical WC particle size for deposition by the cold spray method and that the size criteria arises due to the formation and cohesion mechanisms within the coating layer.Nanostructured test specimens displayed (i) a dense microstructure with little presence of porosity, (ii) a crack free interface between the coating and substrate that indicated good adhesion, and (iii) no observable phase changes. The XRD patterns of each powder and their respective coatings did not have observable peak differences but the diffraction peak broadening of coatings indicated that there was grain refinement during the coating process. Furthermore, all nanostructured as-sprayed WC-Co coatings exhibited Vickers hardness values above HV1000. The nanostructured WC-Co coatings demonstrated adhesive strengths that exceeded the limits of the glue (60 MPa).     

Effect of annealing treatment on the microstructure and properties of cold-sprayed Cu coating

Copper (Cu) coating was deposited by cold spraying, and the electrical resistivity of the coating in both directions parallel and perpendicular to the coating surface was measured to investigate the anisotropy of the coating. Annealing treatment was applied to the coating to examine its effect on the microstructure and properties of the cold-sprayed Cu coating. The examination of coating microstructure evidently revealed that the coating was constituted by the flattened particles, and the interfaces were clearly observed between the deposited particles. The anisotropy in microstructure and electrical resistivity was present in cold-sprayed Cu coating. The electrical resistivity of the as-sprayed coating was higher than that of Cu bulk. Moreover, the electrical resistivity along the direction parallel to the coating surface was lower than that along the perpendicular direction. It was found that annealing treatment led to the enhancement of particle interface bonding and evident recry stallization of the elongated grains and remarkable grain growth as well. The annealed coating presented equiaxed grain structures similar to the annealed Cu bulk with particle interfaces almost disappearing under certain annealing conditions. The coalescence of voids or pores in the coating was clearly observed at high annealing temperatures. Moreover, the annealed coating yielded an electrical resistivity and microhardness comparable to Cu bulk. The original version of this paper was published in the CD ROM Thermal Spray Connects: Explore Its Surfacing Potential, International Thermal Spray Conference, sponsored by DVS, ASM International, and HW International Institute of Welding, Basel, Switzerland, May 2–4, 2005, DVS-Verlag GmbH, Düsseldorf, Germany.     

EBSD研究高纯金溅射靶材的微观组织与织构

溅射靶材的微观组织均匀性、晶粒尺寸大小及晶粒取向分布对溅射性能有着直接的影响。采用电子背散射衍射(EBSD)技术对制备的高纯Au溅射靶材不同区域的微观组织、织构组分和晶界取向差进行了研究。结果表明,高纯金靶材整体晶粒尺寸分布均匀,平均尺寸192.5 nm,边沿及中心晶界取向差分布比较相似,组织均匀性良好,对溅射高质量薄膜十分有利。     

Particle size versus grain size relation in the sprayformed Al-18Si composites

Various hypereutectic Al-18Si-X composites with different average Si particle sizes ranging from 0.2∼30 μm were produced by varying process parameters of spray forming. The effect of the Si particle size in determining the matrix grain size was investigated in order to design the optimum process for producing hypereutectic Al-18Si-X composites with fine microstructures. The experimental results suggested that the Si particle size greater than 2 μm is desirable for retarding the grain coarsening during subsequent forming processes, resulting in the fine microstructure. The observed results on the coarsening behavior of grains during spray-forming were analyzed from the free energy viewpoint.     

Effect of initial α-phase content on microstructure and flexural strength of macroporous silicon carbide ceramics

The effects of the initial α-phase content on the microstructure and flexural strength of macroporous silicon carbide (SiC) ceramics were investigated. When β powder or a mixture of α/β powders containing small (≤3%) amounts of α powder were used, the grains showed a platelet-shape. In contrast, the grains had an equiaxed-shape when α powder or a mixture of α/β powders containing large (≥50%) amounts of α powder was used. The flexural strength increased with increasing α-SiC content in the starting composition, whereas the porosity decreased with increasing α-SiC content. The strength of the macroporous SiC ceramics was affected mostly by the porosity when the grain size was smaller than 10 μm, whereas the strength was controlled by pore size and grain size when the microstructure consisted of large (>10 μm) platelet grains.     

A Study on Microstructure and Dielectric Performances of Alumina/Copper Composites by Plasma Spray Coating

In this study, surfaces of copper plates were coated with a thick alumina layer by the plasma spray coating to fabricate a composite with a dielectric performance that made them suitable as substrates in electronic devices with high thermal dissipation. The performance of alumina dielectric layer fabricated by the plasma spray coating and traditional screen-printing process was compared, respectively. Effects of the spraying parameters and size of alumina particles on the microstructure, thickness, and the surface roughness of the coated layer were explored. In addition, the thermal resistance perpendicular to the interface of copper and alumina and the breakdown voltage across the alumina layer of the composite were also investigated. Experimental results indicated that alumina particles with 5-22 μm in diameter tended to form a thicker layer with a poorer surface roughness than that of the particles with 22-45 μm in diameter. The thermal resistance increased with the surface roughness of the alumina layer, and the breakdown voltage was affected by the ambient moisture, the microstructure and the thickness of the layer. The optimal parameters for plasma spray coating were an alumina powder of particles size between 22 and 45 μm, a plasma power of 40 kW, a spraying velocity of 750 m/s, an argon flow rate of 45 L/min, a spraying distance of 140 mm, and a spraying angle of 90°. It can be concluded that an alumina layer thickness of 20 μm provided a low surface roughness, low thermal resistance, and highly reliable breakdown voltage (38 V/μm).     

等离子喷涂制备靶材的研究进展

靶材是磁控溅射沉积薄膜的原材料,其生产朝着尺寸大型化、高纯度和高利用率等方向发展,目前靶材的主要制备方法从工艺和经济效益上难以满足其生产要求, 等离子喷涂制备靶材是解决上述问题的有效方法之一。通过分析靶材对镀膜性能的影响,总结了靶材制备的技术要求,如纯度、致密度、晶粒尺寸及一致性等。介绍了制备靶材常用的熔融铸造法、粉末冶金法和等离子喷涂法的优点和缺点。熔融铸造法可制备高纯度金属靶材,但是靶材晶粒易粗大;粉末冶金法可制备难熔金属及陶瓷靶材,但是靶材的致密度较低,制作工艺繁琐。这2种方法都难以制作大尺寸靶材。针对等离子喷涂技术在制造靶材方面易于实现大尺寸及管状靶材的制备,并且具有生产工序简单、成本低和可实现废靶修复再利用等特点,重点综述了等离子喷涂制备金属靶材、陶瓷靶材、合金靶材和修复残靶等方面的研究现状。分析认为,喷涂参数、喷涂环境、原料状态、掺杂元素和喷涂后处理等因素是影响靶材性能的关键。通过合理选择喷涂工艺参数,能够实现粉末持续保持熔融状态和充足动量,涂层应力充分释放,以及形成良好的微观组织等方面的协同效果,进一步提升喷涂靶材的纯度和致密度等方面的性能。最后针对等离子喷涂制备靶材的特点,对未来的研究方向进行了展望。     

冷轧变形量和退火制度对超快速加热下5083铝合金晶粒尺寸的影响

利用Gleeble-3500 热模拟系统和电子背散射衍射(EBSD)技术对5083 铝合金的超快速退火组织演变规律进行研究,探讨了快速加热速度、退火温度及冷轧变形量对5083 铝合金晶粒尺寸的影响.结果表明,5083 铝合金经80％的冷轧变形后分别以25、250、500℃/s 的加热速度升温至450℃保温3s 后以40...     

Electro-deposition behaviors of trivalent chromium during pulse plating

Thick trivalent chromium layers were prepared in a modified chromium sulfate bath by pulse plating to replace hexavalent hard chromium coating in industrial fields; layer microstructure development was systematically studied by using electron microscopy and small angle neutron scattering (SANS) to give a model for nucleation and growth behaviors during the pulse plating. Finer columnar grain was formed by pulse plating due to its high nucleation rate at the same current density. Average deposition rate of the trivalent chromium layers is in the range of 32.4 μm/h to 49.7 μm/h. The deposition rate increases as the diameter of cylindrical shape of chromium cluster in a columnar grain is reduced. The highest deposition rate in this study was observed under the conditions of direct current density of 0.4 Acm⁻², combined with a rectangular shape pulse current density of 1.5 Acm⁻² with a 10/2 on-off time ratio. Most of the inner-cracks of the trivalent chromium layers have dimensions in the range of about 39 nm. Ultrasonic agitation during pulse plating resulted in an increase of neutral salt fog spray life, which is related to smaller crack size and broader size distribution in the trivalent chromium.     

Grain refinement and boundary misorientation transition by annealing in the laser rapid solidified 6FeNiCoCrAlTiSi multicomponent ferrous alloy coating

A 6FeNiCoCrAlTiSi multicomponent ferrous alloy coating with simple BCC solid solution phase has been prepared by laser cladding on a low carbon steel substrate. Grain boundary misorientation transition and abnormal microstructure refinement in the coating after annealing at 500 °C have been studied by electron backscatter diffraction (EBSD) observation. Before annealing, the microstructure of the coating is mainly composed of directionally solidified columnar grains with low angle grain boundaries distributed as networks. After annealing, the main phase and microhardness of the coating almost remain unchanged. However, the columnar grains transform to equiaxed refined grains with the grain boundary misorientation transition from low to high angles. This result supports such an argument that the reheating process in post-stage of solidification plays a key role on the grain refinement during rapid solidification process.     

Microstructure and corrosion performance of a cold sprayed aluminium coating on AZ91D magnesium alloy

A pure Al coating was deposited on AZ91D magnesium alloy through cold spray (CS) technique. The microstructure of the coating was characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that the grain interfaces and subgrains formed close to the particle/particle boundaries. Electrochemical tests revealed that the cold sprayed pure Al coating had better pitting corrosion resistance than bulk pure Al with similar purity in neutral 3.5 wt.% NaCl solution. In addition, a mass-transfer step was found to be involved in the corrosion during 10 days immersion.     

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 研究了冷轧00Crl2Ti汽车用铁素体不锈钢的试验钢板的再结晶晶粒显微织构、晶界角度分布和晶粒尺寸及其与力学性能的关系,采用两种不同保温时间的工艺退火试制出退火样,将退火样品首先经线切割、研磨和抛光制备成金相试样,然后,在光学显微镜观察两种退火工艺下的晶粒大小;同时采取EBSD技术扫描获取晶粒取向与亚结构分布图。试验结果表明：两种退火工艺钢板再结晶晶粒的显微织构、晶界角度分布和晶粒尺寸上存在着差异,这种差异印证出两种退火工艺钢板力学性能的差别。此外,利用EBSD还对两种退火工艺的再结晶程度作了分析。     

Effects of Post-spray Heat Treatment on Hardness and Wear Properties of Ti-WC High-Pressure Cold Spray Coatings

In this research, the effects of post-spray heat treatment at 550 and 650 °C for 1 h on a cermet Ti-WC nanostructured coating deposited onto AISI 304 stainless steel substrates by high-pressure cold spray was observed. A metallic Ti interlayer was further used to compensate for stresses resulting from subsequent heat treatment on the developed coating. Microstructural analysis of the as-deposited coating by scanning electron microscopy (SEM) showed mostly fine WC grain (below 1 µm) present in the coating with a few larger 4 µm grains dispersed homogeneously throughout. X-ray diffraction analysis of the as-sprayed coating showed no noticeable evidence of WC decarburization. Heat treatment of the coating caused porosity to decrease from above 1.7% to below 0.5%, traced by SEM image analysis. Post-spray heat treatment promotes the formation of new carbide phases caused by the reactions between the Ti binder and WC grains, resulting in significant increases to Vickers microhardness. Evidence of an SHS reaction that produces TiC with heat treatment is confirmed with SEM image analysis as well as (S)TEM area mapping techniques, further supported by selected area electron diffraction analysis. Three-body sliding wear/abrasion tests have shown that wear resistance of Ti-WC cold spray coatings increases with heat treatment as well. In all, the effect of post-spray heat treatment behavior of nanostructured Ti-WC coating will be compared with that of as-sprayed behavior and WC-Co cold spray coatings.     

Effects of cold rolling parameters on sagging behavior for three layer Al−Si/Al−Mn(Zn)/Al−Si brazing sheets

The effects of intermediate annealing (IA) and the final cold rolling (CR) condition on the microstructure and sagging resistance during brazing were investigated using three layer clad sheets composed of the Al−7.5 wt.%Si alloy (filler, thickness: 10 μm)/Al−1.3 wt.%Mn based alloy (core, 80 μm)/Al−7.5 wt.%Si alloy (filler, 10 μm). Also, the effect of 1.2≈2 wt.% Zn addition into the core on the sagging resistance of the clad sheets was determined. It was revealed that all the clad sheets fabricated by the optimum condition (IA at 690 K and CR to 20≈45%) show excellent sagging resistance with a limited erosion due to the formation of a coarsely recrystallized grain structure in the core during brazing. It was also revealed that the recrystallization behavior of the Al−1.3 wt.%Mn based alloy is hardly affected by the addition of 1.2≈2 wt.%Zn during the brazing cycle. Therefore, the sagging resistance of the clad sheets is found to be governed not by the Zn content added in the Al−1.3wt.%Mn based core, but by the intermediate annealing and final cold rolling condition.     

Impact of Impurity Content on the Sintering Resistance and Phase Stability of Dysprosia- and Yttria-Stabilized Zirconia Thermal Barrier Coatings

Dysprosia-stabilized zirconia (DySZ) is a promising candidate to replace yttria-stabilized zirconia (YSZ) as a thermal barrier coating due to its lower inherent thermal conductivity. It is also suggested in studies that DySZ may show greater stability to high temperature phase changes compared to YSZ, possibly allowing for coatings with extended lifetimes. Separately, the impurity content of YSZ powders has been proven to influence high-temperature sintering behavior. By lowering the impurity oxides within the spray powder, a coating more resistant to sintering can be produced. This study presents both high purity and standard purity dysprosia and YSZ coatings and their performance after a long heat treatment. Coatings were produced using powder with the same morphology and grain size; only the dopant and impurity content were varied. Samples have been heat treated for exposure times up to 400 h at a temperature of 1150 °C. Samples were measured for thermal conductivity to plot the evolution of coating thermal properties with respect to exposure time. Thermal conductivity has been compared to microstructure analysis and porosity measurement to track structural changes. Phase analysis utilizing x-ray diffraction was used to determine differences in phase degradation of the coatings after heat treatment.