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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,009 records · Page 56
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

A Comparative Study of the Microstructure, Mechanical Properties and Corrosion Resistance of Ni- or Fe- Based Composite Coatings by Laser Cladding

Ni- and Fe-based composite coatings were laser cladded on 40Cr steel to improve the surface mechanical property and corrosion resistance, respectively. The microstructure and phase composition were analyzed by x-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) equipped with an energy-dispersive spectrometer (EDS). The micro-hardness, tribological properties and electrochemical corrosion behavior of the coatings were evaluated. The results show that the thickness of both the coatings is around 0.7 mm, the Ni-based coating is mainly composed of γ-(Ni, Fe), FeNi{sub 3}, Ni{sub 31}Si{sub 12}, Ni{sub 3}B, CrB and Cr{sub 7}C{sub 3}, and the Fe-based coating is mainly composed of austenite and (Fe, Cr){sub 7}C{sub 3}. Micro-hardness of the Ni-based composite coating is about 960 HV{sub 0.3}, much higher than that of Fe-based coating (357.4 HV{sub 0.3}) and the 40Cr substrate (251 HV{sub 0.3}). Meanwhile, the Ni-based composite coating possesses better wear resistance than the Fe-based coating validated by the worn appearance and the wear loss. Electrochemical results suggested that Ni-based coating exhibited better corrosion resistance than the Fe-based coating. The 40Cr substrate could be well protected by the Ni-based coating.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Electrochemical Corrosion and In vitro Biocompatibility Performance of AZ31Mg/Al{sub 2}O{sub 3} Nanocomposite in Simulated Body Fluid

In this present investigation, AZ31 alloy nanocomposite was prepared with the inclusion of Al{sub 2}O{sub 3} nanoparticles using innovative disintegrated melt deposition (DMD) process followed by hot extrusion to improve the corrosion resistance and in vitro biocompatibility in simulated body fluid (SBF). This investigation systematically inspected the degradation performances of AZ31 alloy with Al{sub 2}O{sub 3} nanoparticles through hydrogen evolution, weight loss and electrochemical methods in SBF. Further, the surface microstructure with the in vitro mineralization of the alloys in SBF was characterized by XRD, XPS, and SEM/EDS analysis. It was seen that the addition of Al{sub 2}O{sub 3} nanoparticles significantly decreased the weight loss of AZ31 alloy substrates after 336 h of exposure in SBF. The corrosion resistance of the monolithic and nanocomposite samples was evaluated using potentiodynamic polarization tests, electrochemical impedance spectroscopy measurements in short- and long-term periods. Accordingly, the electrochemical analysis in SBF showed that the corrosion resistance performance of the AZ31 alloy enhanced considerably due to the incorporation of Al{sub 2}O{sub 3} nanoparticles as reinforcement. Moreover, the rapid formation of bone-like apatite layer on the surface of the nanocomposite substrate demonstrated a good bioactivity of the nanocomposite samples in SBF.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Corrosion-Resistant Hydrophobic Nanostructured Ni-Reduced Graphene Oxide Composite Coating with Improved Mechanical Properties

In the present work, corrosion-resistant and hydrophobic nickel-reduced graphene oxide (Ni-RGO) composite coating prepared by electroless deposition technique on mild steel (MS), without the use of toxic chemicals, is reported. The field emission scanning electron microscopy micrographs show a uniform composite coating of Ni-RGO with smaller grain size, whereas cuboidal and larger grains were observed in the case of Ni coating on MS. A reduction in crystallite size from 30 to 13 nm with the incorporation of RGO to the Ni matrix was estimated from XRD. The corrosion activity was investigated with potentiodynamic polarization and electrochemical impedance spectroscopy measurements. The surface of Ni-RGO composite coating remained intact, almost undamaged and showed a robust resistance to corrosion with an inhibition efficiency of about 95% in aggressive 3.5 wt.% NaCl solution. Nanoindentation test revealed that the hardness and Young’s modulus of Ni-RGO composite coating are increased by about 25 and 19%, respectively, as compared to Ni coating.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Influence of Thermal Treatment on the Microstructure, Mechanical Properties, and Corrosion Resistance of Newly Developed Ti20Nb13Zr Biomedical Alloy in a Simulated Body Environment

The effect of thermal treatments on the microstructure, hardness, and electrochemical performance in a simulated body fluid were studied for the newly developed (β + α) Ti20Nb13Zr alloy (TNZ) for biomedical applications. The alloy was heat-treated for 1 h at 900 °C and then cooled at different cooling rates. Then, the solution-treated samples were aged at 400, 500, or 600 °C for 5 h. The phase evolution and microstructure of the treated alloy were examined using XRD and SEM/EDX analysis. The mechanical properties were assessed using microindentation. The surface protection performance against corrosion was assessed by potentiodynamic polarization and electrochemical impedance spectroscopic analysis. The obtained results showed that the wide range of microstructure with varied volume fraction and morphology of β and α were obtained with different heat treatment conditions. The different phases’ sizes and distributions influenced the microstructure obtained during the heat treatment, thereby affecting the mechanical properties. The corrosion performance significantly altered with variations in the microstructure of the TNZ alloy as a result of the different thermal treatments. The heat treatment of TNZ conferred enhanced combination of mechanical and corrosion protection compared to that of the commercial Ti6Al4V alloy.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Microstructure of X-120 Steel on CO{sub 2} Corrosion Inhibition by 2-Mercaptobenzimidazole

The use of 2-mercaptobenzimidazole (2MBI) as corrosion inhibitor for API X-120 pipeline with two different microstructures in a CO{sub 2}-saturated 3.5% NaCl solution has been investigated. One microstructure was predominantly martensitic and bainitic (steel A), whereas the second one was mainly ferritic (steel B). It was found that 2MBI behaved as a mixed type of corrosion inhibitor and it changed the corrosion-controlled mechanism. In the uninhibited solution, steel A had a dissolution rate higher than steel B. However, in the presence of inhibitor, dissolution rate for steel A was lower than that for B because the film-formed inhibitor is adsorbed in a better way for steel A which has smaller precipitates distributed in a more homogeneous way than that for steel B.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Elucidating the Effect of TiB{sub 2} Volume Percentage on the Mechanical Properties and Corrosion Behavior of Al5083-TiB{sub 2} Composites

Al5083-TiB{sub 2} in situ composites with 1, 3, and 5 volume percentages of TiB{sub 2} were fabricated. The effect of different volume percentages of TiB{sub 2} reinforcement particles on the mechanical properties and corrosion resistance of these composites was investigated. The hot extrusion process resulted in fragmentation and more homogeneous distribution of TiB{sub 2} particles throughout the Al5083 matrix. Also, the grain size reduced as the amount of TiB{sub 2} reinforcement particles increased which caused the improvement of both the strength and ductility of the material. It was shown that the hardness, the ultimate tensile strength (UTS), and the yield strength (YS) of both the as-cast and extruded materials increased with increasing TiB{sub 2} content. Also, TiB{sub 2} addition combined with the extrusion process improved both UTS and elongation (El.%) of the extruded structures which can be attributed to the presence of TiB{sub 2} particles and obtained microstructural refinement by hot extrusion process. However, the extruded Al5083-5 vol.% TiB{sub 2} composite showed lower ductility in comparison with the extruded Al5083-1 vol.% TiB{sub 2} and Al5083-3 vol.% TiB{sub 2} composites. Moreover, it could be concluded that the corrosion resistance and also the pitting corrosion behavior of the Al5083 alloy do not significantly change in the presence of TiB{sub 2} reinforcement particles.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Corrosion resistance of steel fibre reinforced concrete - A literature review

Steel fibre reinforced concrete (SFRC) is increasingly being used in the construction of civil infrastructure. However, there are inconsistencies among international standards and guidelines regarding the consideration of carbon-steel fibres for the structural verification of SFRC exposed to corrosive environments. This paper presents a review of the published research regarding carbonation- and chloride-induced corrosion of SFRC, and proposes a deterioration theory for cracked SFRC exposed to chlorides and carbonation, based on the damage at the fibre-matrix interface. The review confirms an overall agreement among academics and regulators regarding the durability of uncracked SFRC exposed to chlorides and carbonation. Contrariwise, the durability of cracked SFRC is under discussion at the technical and scientific level, as there is a large dispersion on the experimental results and some of the mechanisms governing the corrosion of carbon-steel fibres in cracks and its effects on the fracture behaviour of SFRC are not fully understood.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Modeling of High-Temperature Corrosion of Zirconium Alloys Using the eXtended Finite Element Method (X-FEM)

Oxidation modeling in modern nuclear fuel performance codes is currently limited by the lack of coupling with mechanics, thus preventing proper description of how high-temperature oxidation impacts mechanical properties. This is mostly due to the fact that the finite difference formalism adopted in corrosion models is incompatible with the direct coupling with mechanics in the finite element modeling employed in modern nuclear fuel performance codes. In this study, a physically based zirconium alloy corrosion model called the Coupled-Current Charge Compensation (C4) model, which was initially developed for operating temperature conditions, has been updated to include high-temperature corrosion in order to provide additional critical information (e.g., oxygen concentration profile) under loss-of-coolant accident (LOCA) conditions—information lacking in existing empirical models. The C4 model was implemented in the MOOSE finite-element framework developed at Idaho National Laboratory, enabling it to be used in the BISON nuclear fuel performance code based on the MOOSE framework. To precisely track the different interfaces at a relatively low computational cost, the eXtended Finite Element Method (X-FEM) was applied in MOOSE. The model’s results were compared to those of existing empirical models as well as metallographic analysis of high-temperature oxidized Zircaloy-4 coupons. Oxygen diffusivities in the a and ß phases resulting from this comparison closely agree with those found in the literature. The C4 model implemented with X-FEM in MOOSE now has the capability to accurately predict oxide, oxygen-stabilized a, and prior ß phase layer growth kinetics under isothermal exposure at high temperature (1000–1500°C). Furthermore, in contrast with the empirical models, the C4 model accounts for the finite thickness of the fuel cladding. It can predict the oxygen concentration profile evolution through the whole cladding, enabling evaluation of the remaining ductile thickness—a crucial variable for modeling the mechanical behavior of the fuel cladding under LOCA. Furthermore, this implementation allows direct coupling with mechanics, at a low computing cost, using finite-element-based nuclear fuel performance codes such as BISON.

36 MATERIALS SCIENCE↗
DOE OSTI2025

In-service corrosion and grain boundary oxidation in neutron-irradiated 316 stainless steel baffle-former bolts

Reactor core internal components such as baffle-former bolts (BFBs) are subjected to significant mechanical stress, corrosive environment, and neutron irradiation from the reactor core during the plant operation. Over the long operation period, these conditions lead to potential degradation and of the bolts. In this work, characterization was performed on the oxidized surface of stainless steel BFBs harvested from a commercial pressurized water reactor (PWR) after 40 years of operation. The analysis shows that a complex multilayered surface oxide with six identified layers formed that is different from 2-layer structure commonly observed in model experiments. The oxide varies by composition – predominantly Fe, Cr, and Ni, grain size, and phase, and has features resembling both unirradiated and radiation/ corrosion experiments likely due to the low radiation flux compared to ion-irradiation or the test reactor radiation. In addition, grain boundary oxidative attack featured a pathway for Fe and other elements to move from the metal matrix to the outermost oxide. In conclusion, the results help assess PWR lifetime extension, put into context previous experimental studies, and provide input for designing experiments combining radiation and corrosion effects.

Baffle-former bolt↗
DOE OSTI2019

Localized corrosion behavior of a single-phase non-equimolar high entropy alloy

In another work, a design method combining computational modeling and empirical knowledge has been reported to establish a more efficient paradigm for developing future corrosion resistant alloys. Using this approach, a single-phase non-equimolar high entropy alloy (HEA) was successfully designed and synthesized. In this work, a detailed experimental investigation of the localized corrosion behavior of this alloy is presented. The HEA was found to possess superior intrinsic pitting resistance and exhibit strong passivity, even in 6 M HCl. The ability of this HEA to initiate and propagate a pit has been studied. The pitting resistance was shown to result from the formation of a passive film with exceedingly strong resistance to breakdown and from a high resistance to pit propagation. Pitting was discovered to be significantly inhibited because of the extremely strong passivity, even in solutions with lower pH and higher chloride concentration than found in a typical local pit environment. The outstanding properties of the HEA validate the approach used for designing corrosion-resistant HEAs.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Effect of electrodeposition temperature on grain orientation and corrosion resistance of nanocrystalline pure nickel

The nanocrystalline pure nickels with different grain orientations were fabricated by direct current electrodeposition process. The grain size slightly decreased with the increasing of electrodeposition solution temperature. However, grain orientation was affected significantly. Comparing with samples obtained at 50 °C and 80 °C, sample obtained at 20 °C had the strongest (111) orientation plane which increased electrochemical corrosion resistance of this sample. At the same time, the lowest (111) orientation plane deteriorated electrochemical corrosion resistance of sample obtained at 50 °C. - Graphical abstract: The increased electrodeposition temperature promoted slightly grain refinement. The grain orientation was affected significantly by electrodeposition solution temperature. The (111) orientation plane of sample increased significantly corrosion resistance. Display Omitted.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Influence of multi-step heat treatments in creep age forming of 7075 aluminum alloy: Optimization for springback, strength and exfoliation corrosion

Multi-step heat treatments comprise of high temperature forming (150 Degree-Sign C/24 h plus 190 Degree-Sign C for several minutes) and subsequent low temperature forming (120 Degree-Sign C for 24 h) is developed in creep age forming of 7075 aluminum alloy to decrease springback and exfoliation corrosion susceptibility without reduction in tensile properties. The results show that the multi-step heat treatment gives the low springback and the best combination of exfoliation corrosion resistance and tensile strength. The lower springback is attributed to the dislocation recovery and more stress relaxation at higher temperature. Transmission electron microscopy observations show that corrosion resistance is improved due to the enlargement in the size and the inter-particle distance of the grain boundaries precipitates. Furthermore, the achievement of the high strength is related to the uniform distribution of ultrafine {eta} Prime precipitates within grains. - Highlights: Black-Right-Pointing-Pointer Creep age forming developed for manufacturing of aircraft wing panels by aluminum alloy. Black-Right-Pointing-Pointer A good combination of properties with minimal springback is required in this component. Black-Right-Pointing-Pointer This requirement can be improved through the appropriate heat treatments. Black-Right-Pointing-Pointer Multi-step cycles developed in creep age forming of AA7075 for improving of springback and properties. Black-Right-Pointing-Pointer Results indicate simultaneous enhancing the properties and shape accuracy (lower springback).

36 MATERIALS SCIENCE↗
DOE OSTI2014

Characterization and corrosion behaviour of CoNi alloys obtained by mechanical alloying

CoNi alloys including Co{sub 30}Ni{sub 70}, Co{sub 50}Ni{sub 50} and Co{sub 70}Ni{sub 30} were prepared via mechanical alloying using Co and Ni powders. The crystallinity and short-range order were studied using X-ray diffraction and X-ray absorption spectroscopy. The results show that the milling process increases the number of vacancies, especially around the Co atoms, while the milling time decreases the crystalline size and enhances the crystallinity. X-ray photoelectron spectroscopy was used to characterise the chemical composition of the samples surface. The magnetic properties were analysed using zero-field cooling, field cooling and a magnetic hysteresis loops. The magnetic saturation moment is approximately 1.05 μ{sub B}/atom; this value decreases with the mechanical alloying time, and it is proportional to the cobalt concentration. The polarization and impedance curves in different media (NaCl, H{sub 2}SO{sub 4} and NaOH) showed similar corrosion resistance values. The corrosion resistance increased in the order NaCl, H{sub 2}SO{sub 4} and NaOH. A good passivation layer was formed in NaOH due to the cobalt and nickel oxides on the particle surfaces. - Highlights: • Ni{sub x}Co{sub 100-x} alloys were synthesized by mechanical alloying • Milling time decrease size and enhances crystallinity. • Oxygen is not present in a significant percentage in bulk but is detected on the surface. • Magnetic saturation moment is 1.05 mB/atom and decrease with mechanical allowing time • Corrosion resistance is higher in NaOH than in NaCl or HCl solutions.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Agro-waste shaped porous Al2O3/Ni composites: Corrosion resistance performance and artificial neural network modelling

Highlights: • Porous Al{sub 2}O{sub 3}/Ni composites were developed with agro-waste pore-forming agents. • The RH and SCB graded composites showed Ni{sub 3}Al{sub 2}SiO{sub 8} and NiAl{sub 2}O{sub 4} spinels respectively. • Superior chemical stability was demonstrated by the Al{sub 2}O{sub 3}-2Ni-RH composite. • The ANN model demonstrated a good performance with R{sup 2} value of approx. 0.99. - Abstract: In the present study, an analysis on the combined effect of nickel (Ni) reinforcement and pore former type in characterizing the corrosion behavior of composite porous alumina ceramics was performed. In order to showcase the potential of the new porous ceramics, pore-forming agents (PFAs) from rice husk (RH) and sugarcane bagasse (SCB) were used in shaping the plain and composite porous alumina samples having sample formulation of Al{sub 2}O{sub 3}-xNi-PFA; x = 0, 2, 4, 6 and 8 wt%. Results showed that the emergence of a highly stable Ni{sub 3}Al{sub 2}SiO{sub 8} spinelloid phase in the RH-graded composites enhanced their chemical stability in the corrosive mediums (10 wt% NaOH and 20 wt% H{sub 2}SO{sub 4}) relative to the plain and the corresponding SCB-graded counterparts. An artificial neural network (ANN) model has been developed for predicting the corrosion behavior of the plain and composite porous alumina ceramics based on the experimental data. The developed ANN model satisfactorily predicted the percent mass losses of the porous ceramics in strong alkali and strong acid solutions with coefficient of determination (R{sup 2}) of approximately 0.99.

36 MATERIALS SCIENCE↗
DOE OSTI2018

The relation between Mn additions, microstructure and corrosion behavior of new wrought Mg-5Al alloys

Highlights: • The influence of high Mn content (1.4 and 3.1 wt%) on Mg-5Al wrought alloys. • Core and shell Al-Mn particles formed when Mn content was 1.4 wt%. • 3.1 wt% Mn effectively mitigate the effect of Fe when it exceeds the tolerance limit. • Large Mn content stabilize the passive layer in long immersion periods. - Abstract: Three wrought Mg-5Al alloys with different Mn contents (0.5, 1.4, and 3.1 wt%) were examined and compared with a reference wrought Mg-5Al alloy. Additions of Mn decreased the grain size and caused precipitation of various Al-Mn intermetallide with different Al/Mn ratio. The corrosion resistance of the Mn-containing alloys significantly increased in comparison to the reference alloy. This contributed to a reduced harmful effect of the impurities, refined microstructure and formation of corrosion products layer. However, further increasing of Mn content caused greater precipitation of the Al-Mn intermetallics, which in its turn increased the galvanic micro-coupling. The alloy with 3.1 wt% Mn additions formed a relatively protective oxide film, which balances the increased number of cathodic particles, and its corrosion rate was very close to that of alloy with 1.4 wt% Mn content.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Stress corrosion cracking mechanism of cold spray coating on a galvanically similar substrate

Here, the chloride-induced stress corrosion cracking (CISCC) mechanism of cold spray (CS) coating on a galvanically similar substrate is investigated. Arc welded 304L stainless steel (SS) specimens are loaded into four-point bend fixtures, cold sprayed with 304L SS, then immersed in boiling MgCl 2 . Interconnected porosity forms through crevice corrosion along CS splat boundaries, allowing corrosive species to penetrate through the CS layer. Nevertheless, the substrate is resistant to CISCC likely because of compressive stress introduced by peening during CS particle impacts. These findings underscore the importance of residual stress in the environmental degradation of CS coatings or repairs of engineering structures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

The corrosion effects of neutron activation of 2LiF-BeF 2 (FLiBe)

The redox effect of activation reactions in molten salts has been previously qualitatively defined but never quantified. Here, we quantify the corrosion effects of neutron activation of FLiBe. Rates of change of activation products are computed for FHR and ARC. The impact of activation reactions on salt chemistry is quantitatively compared to other environmental effects of similar consequences on the salt. The results are applied to a redox control case-study and an irradiation-corrosion experiment. The results are presented in a manner useful to the reactor chemist and designer concerned with corrosion and chemistry control and tritium management in irradiated FLiBe, and design of salt-irradiation experiments.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2012

Nanoscale Chemical Imaging of Zinc Oxide Nanowire Corrosion

Nanoscale chemical images of individual bare and alumina-coated zinc oxide nanowires (NWs) were recorded using tip-enhanced second harmonic generation (SHG) spectroscopy before and after exposure to carbon dioxide and water vapor. The NWs were exposed for 0, 2, 4 and 6 days, and images were collected for the same bare nanowire after each two-day exposure period. Corrosion of the bare ZnO NW to zinc carbonate was evident from far-field and near-field SHG images and simultaneously recorded AFM data. The expected zinc carbonate corrosion product is SHG inactive. The AFM profile of the NW showed vertical and lateral expansion in different regions of the nanowire. The lower resolution far-field SHG signal decreased gradually and uniformly. The near-field SHG signal provided a profile of the evolving NW under investigation with a spatial resolution of ~100 nm which is in agreement with the AFM results. In contrast, alumina-coated ZnO NWs that were exposed in the same gas environment showed reduced, but still observable, degradation. The 3-nm thick alumina protective layer may have been insufficient to fully protect the NW, or the coating may have been incomplete. Thicker coatings preclude the tip-enhanced method. Nevertheless, the ability to monitor corrosion on a nanometer scale is a powerful tool for a fundamental understanding of surface chemical processes and should lead to the discovery of protective layers to prevent or delay degradation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗