Hastelloy C276 Substrates Research Articles

Investigation of Early Stage of Carbon Nanotube Growth on Plasma-Pretreated Inconel Plates and Comparison with Other Superalloys as Substrates.

We investigate the early stage of carbon nanotube (CNTs) growth on Inconel 600 to address the effect of pretreatments such as annealing and plasma pretreatment on growth behavior. In addition, we compare the growth results to other Ni-based superalloys including Invar 42 and Hastelloy C276. The growth substrates were prepared using mechanical polish, thermal annealing and plasma pretreatment. The air annealing was performed at 725 °C for 10 min and plasma pretreatment was subsequently undergone with 10.5 W at 500 °C for 30 min. The annealed and plasma-pretreated substrates exhibited different surface morphologies on the surface and enhanced growth behavior of CNT was observed from the region of particulate surface. The optimized growth temperature, which produces the highest CNT height, was determined at 525 °C for Ni and Inconel 600 and 625 °C for Invar 42 and Hastelloy C276 substrates. The difference of optimal growth temperature is expected to the existence of high temperature elements such as Mn or Mo in the alloys. X-ray diffraction spectroscopy revealed that the formation of roughened oxide layers caused by the pretreatments would promote the nucleation and growth of the CNTs.

Corrosion Properties of Thermally Sprayed Bond Coatings Under Plasma-Sprayed Chromia Coating in Sulfuric Acid Solutions

Plasma-sprayed chromia coatings are known to have excellent corrosion and wear properties in highly acidic conditions at ambient and elevated temperatures, but are not watertight due to their intrinsic porosity. Therefore, in applications involving aggressive environments, the whole component is usually made of a corrosion-resistant alloy, to which the Cr2O3 coating imparts the necessary wear resistance. However, in such aggressive environments, the survival of thermal spray metallic bond layers becomes an issue. The present study deals with the performance in sulfuric acid solutions of coated systems consisting of a Hastelloy C-276 substrate and a plasma-sprayed Cr2O3 top coating with four different intermediate bond coatings. The bond coatings were HVOF-sprayed Ni-20Cr, Hastelloy C-276 and Ultimet alloys and plasma-sprayed tantalum. Open-circuit measurement, electrochemical polarization and electrochemical impedance spectroscopy tests were carried out at room temperature (RT) in solutions with various concentrations. Also, static immersion tests were performed at RT and 60 °C. The results revealed that the HVOF-sprayed Ni-20Cr and Ultimet alloy coatings were significantly attacked by the sulfuric acid electrolyte, especially at 60 °C, whereas the HVOF-sprayed Hastelloy C-276 and plasma-sprayed Ta coatings performed significantly better.

The reactive element effect of yttrium and yttrium silicon on high temperature oxidation of NiCrAl coating

The microstructure formed on the bond coat affects the oxidation resistance, particularly the formation of a protective oxide layer. The adhesion of bond coat and TGO increased significantly by addition of reactive element. In the present work, the effect of yttrium and yttrium silicon as reactive element (RE) on NiCrAl coating was investigated. The NiCrAl (without RE) and NiCrAlX (X:Y or YSi) bond coating were deposited on Hastelloy C-276 substrate by High Velocity Oxygen Fuel (HVOF) method. Isothermal oxidation was carried out at 1000 °C for 100 hours. The results showed that the addition of RE could prevent the breakaway oxidation. Therefore, the coating with reactive element were more protective against high temperature oxidation. Furthermore, the oxidation rate of NiCrAlY coating was lower than NiCrAlYSi coating with the total mass change was ±2.394 mg/cm2 after 100 hours of oxidation. The thickness of oxide scale was approximately 1.18 μm consisting of duplex oxide scale of spinel NiCr2O4 in outer scale and protective α-Al2O3 in inner scale.

Solution deposition of ultrasmooth alumina on long-length metallic substrate for 2G superconducting tapes

Chemical solution deposition of smooth amorphous Al2O3 thin films has been successfully used for planarization of long-length metallic substrates for 2G HTS superconducting wires production. A series of metal-organic precursors based on Al(iPrO)3, Al(acac)3, acetic acid, monoethanolamine (MEA) and diethylenetriamine (DETA) was developed. Correlations between the precursor composition and the features of its two-step thermal-induced transformation to amorphous Al2O3 were studied by 1H NMR, IR spectroscopy and thermal analysis. Utilizing the solutions of {Al(iPrO)3+2.5MEA+6HAcet} in iPrOH and {Al(acac)3+nDETA} in HAcet (n=1−3) as precursors for dip-coating, we obtained the long-length Hastelloy C276 substrate covered by uniform amorphous 50–550nm thick alumina films with surface roughness of about 0.5–1.5nm. A 20m long sample of 2G HTS wire with a commercial level of superconducting critical current of up to 300A was prepared based on Hastelloy substrate tape planarized with Al2O3.

Investigation on influence of deposition rate of YBa2Cu3O7 − δ superconducting film prepared on Hastelloy C276 substrate by spray atomizing and coprecipitating laser chemical vapor deposition

YBa2Cu3O7−δ (YBCO) films were prepared at deposition rates ranging from 10 to 55μmh−1 on CeO2/LaMnO3/MgO/Gd2Zr2O7/Hastelloy C276 substrate by spray atomizing and coprecipitating laser chemical vapor deposition. At a deposition rate of 10μmh−1, a c-axis-oriented YBCO film with a high critical temperature (TC) of 91K and critical current density (JC) of 2.4MAcm−2 was prepared, which showed an epitaxial growth mode of YBCO [001]//CeO2 [100] (YBCO [100]//CeO2 [011]). The full width at half maximum (FWHM) of the ω-scan and that of the φ-scan of the YBCO film were 1.9° and 3.2°, respectively. At a deposition rate of 45μmh−1, an a-axis-oriented YBCO film with a TC of 78K and a JC of 0.4 MAcm−2 was obtained. The YBCO film showed an epitaxial growth mode of YBCO [100]//CeO2 [100] (YBCO [001]//CeO2 [011]) and had the FWHM of 4.9° for the ω-scan and that of 9.5° for the φ-scan, respectively.

Characterization of amorphous yttria layers deposited by aqueous solutions of Y-chelate alkoxides complex

Crack-free amorphous yttria layers were deposited by dip coating in solutions of different Y-chelate alkoxides complex. Three Y-chelate solutions of different concentrations were prepared using yttrium acetate tetrahydrate, yttrium stearic acid as Y source materials. PEG, diethanolamine were used as chelating agents, while ethanol, methanol and tetradecane were used as solvent. Three different combinations of chelating and solvents were used to prepare solutions for Y2O3 dip coating on SUS, electropolished and non-electropolished Hastelloy C-276 substrates. The thickness of the films was varied by changing the number of dipping cycles. At an optimized condition, the substrate surface roughness (rms) value was reduced from ∼50nm to ∼1nm over a 10×10μm2 area. After Y2O3 deposition, MgO was deposited using ion-beam assisted deposition (IBAD), then LaMnO3 (LMO) was deposited using sputtering and GdBCO was deposited using reactive co-evaporation by deposition and reaction (RCE-DR). Detailed X-ray study indicates that LMO/MgO/Y2O3 and GdBCO/LMO/MgO/Y2O3 stack films have good out-of-plane and in-plane textures with strong c-axis alignment. The critical current (Ic) of GdBCO/LMO/MgO/Y2O3 multilayer structure varied from 190 to 420A/cm with different solutions, when measured at 77K. These results demonstrated that amorphous yttria can be easily deposited by dip coating using Y-chelates complex as a diffusion barrier and nucleation layer.

Chemical solution derived planarization layers for highly aligned IBAD-MgO templates

The main goal of this research is to develop a chemical solution derived planarization layer to fabricate highly aligned IBAD-MgO templates for the development of high temperature superconductor (HTS) based coated conductors. The standard IBAD-MgO template needs an additional electrochemical polishing step of the mechanically polished 50 μm-thick Hastelloy C-276 substrates to ensure a flat and smooth surface for subsequent growth of multi-layer buffer architectures, which include: sputtered 80 nm Al2O3; sputtered 7 nm Y2O3; IBAD 10 nm MgO; sputtered 30 nm homo-epi MgO; and sputtered 30 nm LaMnO3 (LMO) layers. We have successfully developed a solution planarization layer that removes the electrochemical polishing step and also acts as a barrier layer. Crack-free, smooth Al2O3 layers were prepared on mechanically polished Hastelloy substrates using a chemical solution process. The average surface roughness value, Ra, for a starting substrate was 9–10 nm. After eight coatings of Al2O3 layer, the Ra was reduced to 2 nm. Highly aligned IBAD-MgO layers with out-of-plane and in-plane textures comparable to the standard IBAD-MgO layers were successfully deposited on top of the solution planarization Al2O3 layers with an Y2O3 nucleation layer using a reel-to-reel ion-beam sputtering system. Both homo-epi MgO and LMO layers were subsequently deposited on the IBAD-MgO layers using RF sputtering to complete the buffer stack required for the growth of HTS films. YBa2Cu3O7−δ (YBCO) films with a thickness of 0.8 μm deposited on these IBAD-MgO templates by pulsed laser deposition showed a high self-field critical current density, Jc, of 3.04 MA cm−2 at 77 K and 6.05 MA cm−2 at 65 K. These results demonstrate that a low-cost chemical-solution-based, high-throughput Al2O3 planarization layer can remove the electro-polishing step and replace sputtered Al2O3 layers for the production of high Jc YBCO-coated conductors.

High-Jc YBa2Cu3O7−δ superconducting film grown by laser-assisted chemical vapor deposition using a single liquid source and its microstructure

A YBa2Cu3O7-δ (YBCO) film was prepared on a multilayer-coated Hastelloy C276 substrate by laser-assisted metalorganic chemical vapor deposition using a single liquid source precursor. A c-axis-oriented YBCO film was grown epitaxially on a (100) CeO2 layer at a deposition rate of 11 μm h−1. A screw dislocation and stacking faults were observed in the cross-section of the YBCO film. The critical current density of the YBCO film reached 2.7 MA cm−2.

The suitability of selected austenitic stainless steels and hastelloy C276 alloys as substrates for thin film deposition using spray pyrolysis

Abstract To detect the suitability of the American Iron and Steel Institute grade 304, 309, 310, 316L steels and Hastelloy C276 substrates for thin film deposition using spray pyrolysis, the substrates were pre-heated between 400–700°C and soaked for one hour. American Society for Testing and Materials standards A262-A, E and G28-A were then applied. The substrates of 304 heated at 400, 600–700°C, the 310 heated between 450–700°C and the as-received 310 were not found suitable. However it was found that the 304, 309, and 310 substrates were suitable up to 550°C, the 316L up to 700°C and the C276 up to 550°C.

Fractal analysis and atomic force microscopy measurements of surface roughness for Hastelloy C276 substrates and amorphous alumina buffer layers in coated conductors

In coated conductors, surface roughness of metallic substrates and buffer layers could significantly affect the texture of subsequently deposited buffer layers and the critical current density of superconductor layer. Atomic force microscopy (AFM) is usually utilized to measure surface roughness. However, the roughness values are actually relevant to scan scale. Fractal geometry could be exerted to analyze the scaling performance of surface roughness. In this study, four samples were prepared, which were electro polished Hastelloy C276 substrate, mechanically polished Hastelloy C276 substrate and the amorphous alumina buffer layers deposited on both the substrates by ion beam deposition. The surface roughness, described by root mean squared (RMS) and arithmetic average (Ra) values, was analyzed considering the scan scale of AFM measurements. The surfaces of amorphous alumina layers were found to be fractal in nature because of the scaling performance of roughness, while the surfaces of Hastelloy substrates were not. The flatten modification of AFM images was discussed. And the calculation of surface roughness in smaller parts divided from the whole AFM images was studied, compared with the results of actual AFM measurements of the same scan scales.

Fracture behavior of coated layer and its influence on critical current of DyBCO coated conductor

The coated conductors are attractive due to their high superconducting properties. As the conductors are subjected to mechanical and electromagnetic stresses in preparation and service, the study on the mechanical behavior and its influence on superconducting properties is demanded for application. In the present work, the DyBa2Cu3O7−δ coated conductor with MgO buffer layer deposited on the Hastelloy C-276 substrate by inclined substrate deposition, prepared at THEVA, was used as the sample. The relation of the deformation and fracture behavior to the change of critical current under applied tensile strain was investigated. The experimental result of tensile test and critical current measurement revealed that the change of critical current with increasing applied tensile strain is caused in two stages; micro-cracking of the coated layer in the fist stage and extensive multiple cracking of the coated layer induced by the discontinuous yielding of the substrate in the second stage.

Fabrication and characterization of ferroelectric PLZT film capacitors on metallic substrates

We have grown ferroelectric Pb0.92La0.08Zr0.52Ti0.48O3 (PLZT) films on Hastelloy C276 (HC) substrates by chemical solution deposition. Samples of 1.15-μm-thick PLZT films were prepared on HC with and without lanthanum nickel oxide (LNO) films as an intermediate buffer layer. On samples with and without LNO buffers at room temperature, we measured dielectric constants of ≈1,300 and ≈450 and loss tangents of ≈0.06 and ≈0.07, respectively. For PLZT films grown on HC with LNO buffer, the dielectric constant increases, while the dielectric loss decreases, with increasing temperature. A dielectric constant of ≈2,000 and loss of ≈0.05 were observed at 150 °C. Samples with LNO buffer also exhibited slimmer hysteresis loops and lower leakage current density when compared to samples without LNO buffer. The following results were measured on samples with and without LNO buffers: remanent polarization (Pr) values of 21.3 and 36.4 μC/cm2, coercive electric field (Ec) values of 41 and 173 kV/cm, and leakage current densities of ≈1.1 × 10−8 and ≈1.6 × 10−7 A/cm2, respectively. The energy storage capability was measured at ≈65 J/cm3 for the PLZT film-on-foil capacitor deposited on HC with LNO buffer.

Fracture and flaking off behavior of coated layer of DyBCO coated conductor under applied tensile strain

The tensile behavior of the DyBa 2Cu 3O 7− δ (DyBCO) coated conductor with MgO buffer layer deposited on the Hastelloy C-276 substrate by inclined substrate deposition (ISD) was studied. The tensile stress–strain curve showed a flat region, characterized by the discontinuous yielding of the substrate due to the Lüders band extension from the gripped portions of the sample. In the area where the Lüders band had passed, the coating layer showed severe multiple transverse cracking due to the localized plastic deformation of the substrate. The flaking off of the coating layers took place at high applied strain, due to the buckling fracture of the coated layers in the sample width direction, accompanied by the interfacial debonding.

Change in fatigue property and its relation to critical current for YBCO coated conductor with additional Cu layer

YBa 2Cu 3O 7− δ , (YBCO) coated conductors with an additional Cu layer are expected to be applied as coils used in superconducting magnetic energy storage, SMES. In the operation of SMES, large cyclic hoop stress is applied to the coated conductor in the longitudinal direction. In the present study, we carried out fatigue tests in liquid nitrogen, LN 2, and measured the critical current, I c , after a specific number of fatigue cycles to clarify its fatigue fracture mechanism. All fatigue tests were carried out under a stress ratio (the ratio of the minimum to maximum load) of 0.5. The frequency of stress cycling was 30 Hz. Our results showed that the addition of a Cu layer increased the fatigue strength after 10 6 cycles, F N = 10 6 , by about 19%. Decrease of I c was more than 30% of the initial critical current, I c 0, without loading at the point of final overall fracture when the maximum load in the stress cycles was close to that corresponding to irreversible strain. Furthermore, microscopic observation and the change in I c showed that fatigue fracture mainly initiated from the Hastelloy C-276 substrate. Fatigue fracture also initiated from the Cu layer, but only when the maximum load was approximately F N = 10 6 .

Substrate surface treatment and YSZ buffer layers by IBAD method for coated conductors

In this work, an Ion Beam Assisted Deposition (IBAD) system was utilized to fabricate Yttria-Stabilized Zirconia (YSZ) template films for coated conductors. The surface of the Hastelloy C276 substrate was modified by rolling and electropolishing. The effect of the electropolishing parameters of the substrate on the texture of the YSZ buffer layers was studied. The electropolishing current and time were optimized for short samples of 1 cm×1 cm square shape as 1 A and 60 s, respectively. And the relationship between the roughness of the substrate surface and the texture of the YSZ layer is discussed. Reel-to-reel metal tape moving apparatus was installed and used to produce meter-long buffer layer for coated conductors. The YSZ template film was deposited by IBAD method on meter-long Hastelloy tape with tape shifting speed of 15–20 m/h, and the thickness of the buffer layer was up to about 1.7 μm. The Hastelloy substrate surface was measured by Atomic Force Microscope. The thickness of the YSZ films over length was measured by Thermal Field Emission Scan Electronic Microscopy. X Ray Diffraction Ω-scan and ϕ-scan measurements were performed in order to examine the out-of-plane and in-plane texture of the YSZ buffer layers, respectively.

Improvement of Strain Tolerance in RE-123 Coated Conductors by Controlling the Yielding Behavior of Hastelloy C-276 Substrates

Mechanical properties of Hastelloy C-276 substrate with different pre-treatment were investigated. Discontinuous yielding was observed in the solution treated substrate after annealing at the maximum process temperature of IBAD and ISD. In the smooth rolled substrates, yield strength higher than 1 GPa can be attained and even after annealing continuous yielding can be maintained. Annealing enlarges elastic limit by pinning of the mobile dislocations. Microstructure observation using transmission electron microscopy shows that two kinds of candidates for the pinning site of the dislocations exist such as precipitates and short range ordering region in the discontinuous yielding substrate. Improvement of strain at quenching was confirmed by utilizing continuous yielding substrate with higher elastic limit.

Tensile fracture behaviour of RE-123 coated conductors induced by discontinuous yieldingin Hastelloy C-276 substrate

We investigated the intrinsic strain effect on critical current,Ic, and tensile fracture behaviour in the RE-123 coated conductors(RE = Y, Dy or Sm) with Hastelloy C-276 substrates. It is found thatthe SmBCO coated conductors exhibit an intrinsic strain effect onIc which is similar to that in the DyBCO ones.Ic decreases monotonically with increasing applied tensile strain but it can recover reversiblyup to the strain of 0.32% when the strain is relieved. Quenching occurred for the coatedconductors with Hastelloy C-276 substrate in the narrow strain region of 0.27–0.35%regardless of the buffer layers and superconducting materials. In order to reveal the reasonfor such quenching, we measured mechanical properties of the Hastelloy C-276 tapes aloneand coated conductors at 77 K. The as-received and as-polished Hastelloy tapes showcontinuous yielding, which results from homogeneous plastic deformation. On the otherhand, the Hastelloy tape annealed at 963 K corresponding to the deposition conditionfor the superconducting layer exhibits discontinuous yielding. In the annealedHastelloy tapes, occurrence of Lüders bands is observed, indicating that plasticdeformation progresses inhomogeneously. Discontinuous yielding is also confirmed in thecoated conductor. The yield strains of the coated conductors are almost identicalto the strains at quenching. Characteristic fracture behaviour is observed, thattransverse crack arrays are initiated from the tape edge and they propagate intothe central part. The crack arrays orient to a certain angle to the loading axis,which is similar to that of the Lüders bands. The similarities in the initiation siteand the angle to the loading axis between the Lüders bands and the crack arraysand close values of quenching strains to the yielding one strongly suggest thatquenching is attributable to the discontinuous yielding in the Hastelloy substrate.

Influence of the Ion-to-Atom Ratio on the Structure of CeO2 Buffer Layer by Ion Beam Assisted E-Beam Evaporation

Using ion-beam assisted e-beam evaporation with the ion beam directed at 55° to the normal of the film plane, (200) oriented CeO2 films with biaxial texture were deposited on Hastelloy C276 substrates at room temperature. The crystalline quality and in-plane orientation of films was investigated by X-ray diffraction 2θ-scan and Φ-scan, atomic force microscopy (AFM). It was shown that the in-plane and out-of-plane textures of the CeO2 films were controlled by the deposition parameters. The orientation of the films was studied as a function of ion-to-atom ratio and film thickness. The ion-to-atom ratio was varied by independently adjusting the deposition rate and the ion current density. Under optimum condition, (200) textured CeO2 films have been successfully grown on Hastelloy C276.

Study of the growth of biaxially texturedCeO2 films during ion-beam-assisted deposition

Biaxially textured CeO2 films were deposited on Hastelloy C276 substrates at room temperatureusing ion-beam-assisted e-beam evaporation with the ion beam directed at55° to the normal of the film plane. The crystalline structure andin-plane orientation of films were investigated by x-ray diffraction2θ-scanand ϕ-scan. The orientation of the films was studied as a function of ion-to-atom ratio andfilm thickness. The ion-to-atom ratio was varied by independently adjusting thedeposition rate and the ion current density. Under optimum condition, (200) texturedCeO2 films have been successfully grown on Hastelloy C276.

Morphological and structural control of nanostructured <100> oriented CeO2 films grown on random metallic substrates

CeO2 (cubic fluorite) thin films have been deposited on no-rolled Hastelloy C276 substrates by metal-organic chemical vapour deposition (MOCVD) from the Ce(hfa)3·diglyme [Hhfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione; diglyme = (CH3O(CH2CH2O)2CH3)] precursor. The X-ray patterns of all samples grown in the 350–550 °C temperature range point to the formation of oriented CeO2 films, while at higher deposition temperatures (650–850 °C) random CeO2 films are formed. XRD data indicate that 450 °C is the best deposition temperature. Detailed studies of the influence of all deposition parameters (precursor vaporization temperature, O2 and Ar gas flows, deposition temperature and time) on the CeO2 film growth have been carried out. There is evidence that the deposition process occurs in a mass transport regime. A suitable rationale for the observed textural changes vs. temperature has been proposed and the present columnar grain morphology, depending upon deposition temperatures, has been related to the zone model proposed by Mochvan and Demchishin for physical vapour deposition processes.