Papers by Keyword: EB-PVD

Abstract: Yttria Stabilized Zirconia (YSZ) coating was developed using electron beam physical vapour deposition as a top coat material for thermal barrier application. In the present study, attempt to develop YSZ films by evaporating ZrO₂ stabilized with 8 wt% Y₂O₃ powder using EBPVD technique. YSZ films were deposited on Inconel-718 (Ni-Cr-Fe) substrate by varying the substrate temperature in the range of 673 K to 1073 K. The deposited films have shown good adherence to the substrate and exhibit uniform dense microstructure. The effect of substrate temperature, phase and surface morphology were investigated by XRD, AFM and SEM. The film deposited at 673 K shows crystalline nature and the crystallinity of the deposited films increase with increasing substrate temperature. The surface roughness of the films increases with increase in the deposition temperature due to the increase in crystallinity of the films. SEM images shows that the films are grown with triangular shaped morphology. Nanomechanical characteristics of the tetragonal phase of the YSZ films were investigated by nanointendation technique and the young’s modulus of the coating was found to be 118 GPa.

Abstract: The role of thermal barrier coatings is to ensure heat resistance of elements in the hot section of turbofan aircraft engines in high temperatures. Stages of the production process are made up of preparing the base material, forming the aluminide interlayer by chemical vapour deposition method and depositing of the ceramic coating. The paper presents results of tests into microstructure of ZrO₂ and Y₂O₃ ceramic coatings formed by EB-PVD method. The microstructure was assessed in several spots of the turbine blade of a high pressure turbofan engine by means of determining the coating thickness as well as height and width of ceramic columns, depending on the forming conditions.

Abstract: TiAl based micro-laminated sheet was deposited by electron beam physical vapor deposition (EB-PVD) with dual-target in this work, and then the microstructure and phase analysis of as-deposited samples were studied by SEM, XRD and TEM. The results show that the difference of melting points between Ti and Al led to the distinctive structure: the Ti-Al layers were mainly constituted of equiaxed grains and Ti layers were constituted of column grains. Because of the deviation of saturated vapor pressure between Ti and Al element, the component showed a gradient change periodically along the normal direction of Ti-Al layers and results in several sub-layers. The Ti layers, Ti-Al layers and interfacial layers were constituted of α phase, γ+α₂ phase and α₂ phase respectively.

Abstract: Ni₃Al based alloy IC10 has been developed for turbine blades and vanes of advanced aero-engines and other high temperature structural components. Conventional two-layered structure thermal barrier coatings (TBCs) were produced by EB-PVD onto Ni-based superalloy. The thickness of bond coat and top coat was approximately 60μm and 120μm, respectively. After thermal barrier coatings were produced, it was heated at 1523K for 2hs, 6hs, 14hs and 20hs under 1×10^-2Pa, respectively. After heat treatment was done, the thermal cyclic test was carried out by exposure to air at 1373K for 0.5h, and then cooled to room temperature within 5 minutes by forced air cooling. Scanning electron microscopy (SEM) was employed to study the microstructure of the coatings. After thermal cycled in air at 1373K for TBCs without heat treatment at 1523K, its lifetime is about 810 hours. After 760hs thermal cycles, the spallation occurred on the TBCs that the heat treatment was treated at 1523K for 2hs. The lifetime of TBCs, which the heat treatment was treated at 1523K for 6hs, was 710hs. The lifetime of TBCs, which the heat treatment was treated at 1523K for 14hs and 20hs, was 600hs and 560hs, respectively. The results showed that, with the increasing of the time of heat treatment, the weight gain increased evidently during thermal cycled. The results showed that heat treatment at 1523K affect the lifetime of TBCs during thermal cyclic evidently.

Abstract: Ti-Al multilaminate composite was prepared by high-power EB-PVD technology, and under vacuum condition, the samples were annealed at different temperatures. The changed microstructure of the samples after annealing was characterized by XRD, SEM and EDS. The experimental results show that, with the increment of temperature, the ordered phases reduce due to the diffusion of Al into Ti, and the breakdown of layered architecture was induced mainly by pore formation, grain growth and the grain boundary grooving.

Abstract: Titanium nitride (TiN) is a hard material, often used as coating to improve the wear properties of titanium alloys in machining, implant and aerospace applications. Electron Beam Physical Vapor Deposition (EB-PVD) is a technique which a target anode is bombarded with an electron beam given off by a charged tungsten filament under high vacuum, producing a thin film in a substrate. In this work, results of TiN films depositions on Ti-13Nb-13Zr substrates by EB-PVD are studied. Titanium targets were obtained by a purified ingot and the substrates produced by powder metallurgy. Sintered samples of Ti-13Nb-13Zr and TiN layers were characterized by X-ray diffraction, scanning electron microscopy, Vickers microhardness and wear tests. The TiN films presented high hardness values, continuity and large thickness. The coatings improved the tribological properties of the substrate due to high adhesion and low wear rate.

Abstract: Multilayer coatings are synthetic structures constituted by alternate layers of different materials. The technological applications of the multilayer coatings can involve optical, electromagnetism and wear areas. The target of this work is the production of multilayer TiN/ZrN coatings by Electron Beam Physical Vapor Deposition (EB-PVD) over titanium alloys produced by powder metallurgy. P/M-Ti-35Nb-7Zr-5Ta cylindrical samples used as substrates were produced by mixing of the elemental powders with subsequent cold pressing steps and sintering at 1400°C, in high vacuum. TiN/ZrN coatings were obtained by evaporation of alternating Ti and Zr cylindrical targets. The multilayers were characterized by optical and scanning electron microscopy (SEM), chemical analysis via energy dispersive spectrometry (EDS) and Vickers indentation. Besides the possibility of obtaining several layers, the results show coatings with coherent columnar structure, low discontinuity, large and homogenous thickness and high adhesion to substrate.

Abstract: One multiscalar microlaminate (MSML) with 5 thick layers of NiCoCrAl whose thickness were different interspersed with 66 thin layer stacks of NiCoCrAl/YSZ was fabricated by EB-PVD. Uniaxial tensile testing was performed and fracture was examined using SEM. The results show that the microlaminate exhibits brittle-like behavior without macroscopic plastic deformation in room temperature tensile tests and the maximum engineering stress is 212MPa. Examination of fracture surfaces from the samples reveals that ceramic layers fail by intergranular brittle fracture between columns, but metal layers display features of both ductile and brittle fracture. It is also found that the thicknesses of metal layers have a great effect on their failure modes. And interfacial debonding and bridging metal layers are observed. Moreover, the resistance of crack propagation in the microlaminate is discussed.

Abstract: High silicon electrical steel prepared by EB-PVD was subjected to high temperature rapid thermal annealing and subsequent pack rolling. The phase composition and Fe configurations were characterized by X-ray diffraction and Mössbauer spectroscopy. The results show that the as-deposited, as-annealed and as-rolled samples mainly consist of DO₃ ordering phase and the as-deposited electrical steel is composed of six kinds of Fe sites corresponding to 333.8KOe, 319KOe, 302 KOe, 284 KOe, 249 KOe, 196 KOe, respectively, while the Fe site corresponding to 196 KOe hasn’t been found in the other two samples. Moreover, the other two samples show a larger Fe site occupancy corresponding to 284 KOe.

Abstract: The effect of pressures on microstructure and properties of as-deposited high silicon electrical steel by EB-PVD during hot pressing was studied. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the phase composition and morphology; the density and electrical resistivity were measured using the bottle method and four-probing method, respectively. It was found that the density increased from 7.25×10³ kg/m³ to 7.5 ×10³ kg/m³, while the electrical resistivity decreased from 85µΩ•cm to 75µΩ•cm with the increase of the pressure from 30 MPa to 60 MPa.