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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 1,045 records · Page 58
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Cyclic Corrosion and Chlorination of an FeCrAl Alloy in the Presence of KCl

The KCl-induced corrosion of the FeCrAl alloy Kanthal® APMT in an O 2 + N 2 + H 2 O environment was studied at 600 °C. The samples were pre-oxidized prior to exposure in order to investigate the protective nature of alumina scales in the present environment. The microstructure and composition of the corroded surface was investigated in detail. Corrosion started at flaws in the pre-formed α-alumina scales, i.e. α-alumina was protective in itself. Consequently, KCl-induced corrosion started locally and, subsequently, spread laterally. An electrochemical mechanism is proposed here by which a transition metal chloride forms in the alloy and K 2 CrO 4 forms at the scale/gas interface. Scale de-cohesion is attributed to the formation of a sub-scale transition metal chloride.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Effect of Oxidizing Impurities on the Corrosion Behavior of Structural Alloys Exposed to MgCl 2 Molten Salt Vapor

The corrosion behavior of structural alloys SS304 and IN617 when exposed to vapors of MgCl 2 molten salt at 764 °C for 100 h in an argon atmosphere was investigated as a function of the level of oxidizing impurities (e.g., NaOH) present in the salt. Increasing the concentration of oxidizing impurities in the salt caused an increase in corrosion in both structural alloys, as measured by Cr depletion layers. A poorly adhered oxide scale layer containing Mg, Al, and Cr was observed on the surface of the metals, and local attack was observed as well. The Ni-based IN617 showed lower Cr depletion and less scale formation than the Fe-based SS304. These results demonstrate that oxidizing impurities in the molten salt will impact the vapor phase corrosion for structural members exposed to the molten salt headspace. This finding is highly relevant for understanding the effects of the vapor phase in molten salt applications, including molten salt thermal energy storage, molten salt nuclear reactors, and molten salt electrochemistry.

25 ENERGY STORAGE↗
DOE OSTI2017

Corrosion Behavior of Carbon Steel Coated with Octadecylamine in the Secondary Circuit of a Pressurized Water Reactor

Corrosion and particle deposition in the secondary circuits of pressurized water reactors can be mitigated by alternative water chemistries featuring film-forming amines. In the present work, the corrosion of carbon steel in secondary side water with or without octadecylamine (ODA) is studied by in situ electrochemical impedance spectroscopy, combined with weight loss/gain measurements, scanning electron microscopy and glow-discharge optical emission spectroscopy. The impedance spectra are interpreted using the mixed-conduction model to extract kinetic parameters of oxide growth and metal dissolution through it. From the experimental results, it can be concluded that ODA addition reduces the corrosion rate of both fresh and pre-oxidized carbon steel in secondary circuit significantly by slowing down both interfacial reactions and transport through the oxide layer.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effects of Scandium Addition and T7 Heat Treatment on Thermal Stability and Corrosion Properties of A201 Alloy

This study elucidates how scandium addition and T7 heat treatment affects thermal stability and corrosion properties of A201 alloy. The as-cast and the T7 heat-treated specimens were thermally exposed at 300 °C for 120 h to investigate the evolution of the Sc-free and the Sc-containing alloys. The results indicated that adding 0.6 wt.% scandium to A201 alloy could produce Al{sub 3}Sc, W phase (Al{sub 8-5.4}Cu{sub 6.6-4}Sc) and grain refinement, significantly enhancing the hardness and tensile strength in as-cast condition. The as-cast A201 alloy containing Sc also showed the least loss of hardness and strength during thermal exposure at 300 °C. In addition, the presence of W phase weakened the peak hardness and tensile strength of the Sc-containing A201 alloy during T7 heat treatment. Adding Sc to A201 alloy increased corrosion resistance in T7 heat-treated condition, but slightly decreased corrosion resistance in as-cast condition.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effects of Voltage on Microstructure and Corrosion Resistance of Micro-arc Oxidation Ceramic Coatings Formed on KBM10 Magnesium Alloy

Micro-arc oxidation (MAO) coatings on KBM10 magnesium alloy were prepared in an electrolyte system with sodium silicate, potassium hydroxide, sodium tungstate, and citric acid. The effects of voltage on the microstructure and corrosion resistance of MAO coatings were studied using stereoscopic microscopy, scanning electron microscopy, x-ray diffraction, scratch tests, potentiodynamic polarization, and electrochemical impedance spectroscopy. The results showed that the roughness of the MAO coatings, diameter, and number of pores increase with the increase in voltage. The coating formed at the voltage of 350 V exhibited the best adhesive strength when evaluated by the automatic scratch tester. The coatings were mainly composed of MgO, MgWO{sub 4}, and Mg{sub 2}SiO{sub 4}, and the content of Mg{sub 2}SiO{sub 4} increased with the increase in voltage. The corrosion resistance of MAO coatings could be improved by changing the applied voltage, and the best corrosion resistance of MAO coating was observed at the voltage of 350 V.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Tribological and Corrosion Properties of Coatings Produced by Plasma Electrolytic Oxidation on the ZA27 Alloy

In this paper, a continuous and dense coating was deposited on samples of the ZA27 alloy through the plasma electrolytic oxidation (PEO) process to improve its wear and corrosion performance. A nontoxic and environmentally friendly inorganic salt, Na{sub 2}SiO{sub 3}, is chosen as electrolytes with different concentrations. The effect of the concentration of Na{sub 2}SiO{sub 3} aqueous solutions on the coating performances was investigated. The coatings with 3Al{sub 2}O{sub 3}·2SiO{sub 2} (mullite), Zn{sub 2}SiO{sub 4} and Al{sub 2}O{sub 3} (either crystal phase or with some amorphous SiO{sub 2} phases) were formed by the PEO processes. It was found that the coating thickness increased with the increase in electrolyte concentration. However, the wear and corrosion resistance performance of the coatings did not improve as the coating’s thickness increased. This was due to the fact that the coating produced with electrolytes of 10 g/L has a porous structure with large pore size. Among all the samples, coating produced by 15 g/L Na{sub 2}SiO{sub 3} has the best wear and corrosion resistance, which is attributed to its continuous and dense structure with thickness of about 47 μm.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Corrosion and Mechanical Degradation of Ni-Ti Superelastic Alloy in Neutral Fluoride Solution

The corrosion behavior and mechanical degradation of Ni-Ti superelastic alloy in neutral fluoride solution were investigated with a focus on the effect of temperature during immersion. Corrosion was accelerated by increasing the temperature, and mass loss increased with immersion time. Furthermore, Ti ions (Ni ions) preferentially dissolved in the early (later) stage of immersion. The tensile strength of the immersed specimen decreased when the mass loss was approximately 0.040-0.050 mg/mm{sup 3}. The fracture mechanisms of specimens immersed in 2.0% NaF solution were active path corrosion at room temperature and presumably hydrogen embrittlement at 80 °C. For long-term (e.g., 180 days) immersions at 80 °C, hydrogen embrittlement did not occur, because the absorbed hydrogen diffused to the center of the immersed specimens, rendering the hydrogen distribution comparatively uniform. These findings suggest that the fracture mechanism of immersed specimens can change as a result of the temperature during immersion.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Comparative Atmospheric Corrosion Behavior of a Mild Steel and an Interstitial Free Steel

The present work discusses the effect of structure and morphology of rust on the corrosion behavior of a mild steel and an interstitial free steel exposed to open atmosphere for 2 years involving extreme weather conditions, where temperature varies from 2-3 to 45 °C, rainfall varies from 10 to 320 mm and humidity varies from ~ 20 to 75%. Effect of duration of atmospheric exposure, change in morphological characteristics of rust, and atmospheric parameters, such as temperature, humidity, rain and SO{sub 2} content on the corrosion behavior of both the steels was analyzed. Corrosion resistance of the interstitial free steel was better than the mild steel due to lower carbon content and better compactness of the rusts formed on the interstitial free steel.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Corrosion Performance of Composite MAO/TiO{sub 2} Sol–Gel Coatings on Magnesium Alloy AZ91D

In this paper, the composite coatings on the surface of magnesium alloy were successfully prepared by the combination of micro-arc oxidation (MAO) and sol–gel method. Oxide ceramic layers were formed on AZ91D magnesium alloy using MAO process. The sol–gel layers were coated on MAO ceramic layers. The composition of the composite coatings was analyzed by x-ray diffraction and x-ray photoelectron spectroscopy. The microstructure of the composite coatings was analyzed by scanning electron microscope. The results show that the composite coatings can reduce the gap membrane effectively. The polarization curves and electrochemical impedance spectroscopy were used to evaluate the corrosion resistance. The results of corrosion tests show that the sol–gel layer enhances the corrosion resistance of the magnesium alloys significantly.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of Lithium on the Discharge and Corrosion Behavior of Mg-3 wt.% Al Alloy as the Anode for Seawater Activated Battery

The discharge and corrosion behavior of Mg-3 wt.% Al alloys added with different contents of lithium in 3.5 wt.% NaCl aqueous solution is studied by electrochemical methods and microstructure characterization. The results indicate that adding 4 wt.% lithium severely promotes the self-corrosion and the addition of 12 wt.% lithium is not valuable to the spalling of discharge products. In contrast, doping Mg-3 wt.% Al with 8 wt.% lithium negatively shifts the discharge potentials and inhibits the self-discharge, attributed to the dual-phase structure of α-Mg plus β-Li that removes the discharge products and favors the uniform dissolution in the course of discharge. Moreover, the multi-pass rolling with 40% reduction could tailor the microstructure of Mg-3 wt.% Al-8 wt.% Li alloy and further enhance its discharge activity, even though the corrosion resistance is slightly reduced. This means that the rolled Mg-3 wt.% Al-8 wt.% Li sheet is suitable to serve as the anode for seawater activated battery.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Enhancement of Hot Corrosion Resistance of Modified 9Cr-1Mo Steel Through Surface Nanostructuring and Pre-oxidation

Nanosize grains of ~ 65 nm were developed with large misorientation angles of grain boundaries in surface region of normalized and tempered modified 9Cr-1Mo steel by ultrasonic shot peening (USSP) with hard steel balls of 3 mm diameter. The surface roughness and the depth of nanostructured surface region were found to increase with the duration of USSP from 0.5 to 5 min. Hot corrosion tests were performed for the Un-USSP and the samples USSPed for the durations of 0.25 and 1.5 min and also for the samples subjected to USSP and subsequently pre-oxidation at 600 °C for 4 h. The hot corrosion resistance at 600 °C under 100% NaCl coating was significantly improved by USSP for 1.5 min and subsequent pre-oxidation at 600 °C for 4 h. The results are discussed in terms of the formation of more uniform and effective protective iron–chromium oxide layer on the USSPed surface from the subsequent pre-oxidation treatment, prior to hot corrosion of the specimens under 100% NaCl coating at 600 °C.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Tribo-corrosion and Albumin Attachment of Nitrogen Ion-Implanted CoCrMo Alloy During Friction Onset

In this paper, CoCrMo alloy surface was implanted with 100 keV nitrogen ions to modify it. Bovine serum albumin (BSA) adsorption and the initial behavior of tribo-corrosion in the simulated system were studied. Nitrogen ion implantation can promote BSA dynamic adsorption due to the change of friction and wear mechanisms. From the tribo-corrosion test results, the open circuit potential (OCP) increased to about 0.6 V and the coefficient of friction (COF) decreased to about 0.2 for the nitrogen ion-implanted CoCrMo compared with the untreated sample before the modified layer failure. The point when the open circuit potential and the coefficient of friction changed during long wear time (1, 2 and 4 h) is considered the sign of the worn through modified layer. Then, the OCP of the implanted sample rose by 0.3 V compared with the untreated sample, and the COF remained at around 0.3, which is lower compared with the COF of untreated sample after the modified layer has been worn through. Thus, nitrogen ion implantation not only improved wear and corrosion resistance of the CoCrMo alloy, but also promoted BSA adsorption on the CoCrMo alloy surface, which effectively reduced the wear volume and metal ions release.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Influence of Multidirectional Forging on Microstructural, Mechanical, and Corrosion Behavior of Mg-Zn Alloy

Multidirectional forging (MDF) was applied to Mg-6%Zn alloy up to 5 passes successfully at 280 °C. MDF-processed materials were characterized using optical microscope, scanning electron microscope, electron backscatter diffraction, transmission electron microscope, and x-ray diffraction. Obtained results showed a significant reduction in grain size (up to 3.8 μm) having a large fraction of high-angle grain boundaries after 5 passes of MDF process. Maximum tensile strength of 230 MPa was achieved for 5-pass MDF-processed Mg-6%Zn alloy which is about ~ 2.0 times higher in comparison with that of homogenized alloy (117 MPa) and was attributed to higher dislocations density and grain refinement. Corrosion behavior of the alloy was investigated in 0.1 M NaCl solution using potentiodynamic polarization test, electrochemical impedance spectra analysis, and immersion tests. It was found that the corrosion rate of 5-pass MDF sample improved (0.34 mm/year) ~2.5 times in comparison with that of homogenized Mg-6%Zn alloy (0.86 mm/year) due to fine grain structure, which creates more grain boundaries that act as a corrosion barrier.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effects of Ce Addition on Grain Boundary Character Distribution, Corrosion Behavior and Impact Toughness of AISI 204Cu Stainless Steel

In this study, the effects of Ce addition on grain boundary character distribution, corrosion behavior and impact toughness of AISI 204Cu stainless steel were investigated. The results revealed that rare earth Ce affected the characteristics and size of inclusions, and the change in the austenite grain size was attributable to Ce multi-phase inclusions as the core of heterogeneous nucleation in stainless steel. The high adjacent probability of γ-fiber textures comprising {111} 〈110〉 and {111} 〈112〉 components was available for more ∑3{sup n} boundaries with increasing Ce contents, which was believed to have a contribution to the enhancement of corrosion resistance. Meanwhile, the austenite grain refinement and ∑3{sup n} boundaries increment were beneficial for the impact toughness improvement of Ce-added steel by increasing the difficulty of crack initiation and propagation. Adding excessive Ce caused a decline in the corrosion behavior and impact toughness of 204Cu stainless steel.

36 MATERIALS SCIENCE↗
DOE OSTI2019

The Mechanical and Corrosion Properties of Hot-Rolled TiB{sub 2}/Ni Composites

To quickly prepare TiB{sub 2}/Ni composites at low temperatures, a method combining spark plasma sintering and hot rolling was used. This paper presents the preparation, microstructural and mechanical properties, strengthening mechanism and corrosion properties of TiB{sub 2}/Ni composites in detail. X-ray diffraction analysis shows that the texture degree of the TiB{sub 2}/Ni composites after hot rolling greatly differed from that of the as-rolled pure Ni samples. The addition of TiB{sub 2} particles limited grain growth in the Ni matrix and led to grain refinement. Dislocation strengthening, grain refinement strengthening and load transfer strengthening contributed to a 30% increase in the tensile strength compared to that of the as-rolled pure Ni. In addition, the strengthening mechanism of the mechanical property reinforcement was analyzed. The electrochemical test results demonstrate that the as-rolled pure Ni exhibited a lower corrosion current density and corrosion resistance than the other as-rolled TiB{sub 2}/Ni composites fabricated in this paper. This work demonstrates a new approach for fabricating composites in less time at lower preparation temperatures than conventional methods.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Studies on Ti, Zn and Ti + Zn Bilayer Coatings on Interstitial Free Steel for Enhancement of Wear and Corrosion Resistance

The present study concerns a detailed investigation of the microstructure, phase identity, composition, residual stress, wear and corrosion behavior of Ti, Zn and Zn + Ti coatings developed on IF steel by sputter deposition technique. A significant improvement in average microhardness (350-700 VHN) is noticed following sputter deposition compared to that of as-received IF steel (190 VHN). The highest microhardness recorded is 500 VHN for Ti, 350 VHN for Zn and 700 VHN for Ti + Zn bilayer, respectively. Improvement in surface hardness is accompanied by a marked improvement in wear resistance of the sputter-deposited surface against hardened steel ball. The corrosion rate of coated sample in 3.56 wt.% NaCl solution is marginally decreased (2.95 × 10{sup −2} to 3.25 × 10{sup −2} mm/year) as compared to that of as-received IF steel (3.55 × 10{sup −2} mm/year). Ti-deposited IF steel registers the minimum corrosion rate (2.95 × 10{sup −2} mm/year) among all the coated samples.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Hot Corrosion Behavior of Ni20Cr Alloy in NaVO{sub 3} Molten Salt

The hot corrosion behavior of Ni20Cr alloy was evaluated in NaVO{sub 3} at temperatures of up to 700 °C and compared to Inconel 600. The performance of both the alloys was evaluated using electrochemical measurements, such as potentiodynamic polarization, linear polarization resistance, and electrochemical impedance spectroscopy measurements, as well as a cyclic corrosion test. The results show that the Ni20Cr alloy has better corrosion performance than the Inconel 600. The better performance of the Ni20Cr alloy was due to its ability to develop a stable protector oxide (Cr{sub 2}O{sub 3}) on its surface.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Morphology and Mechanical, Corrosive, and Antibacterial Behaviors of Indirectly Extruded Zn-0.05wt.%Mg-(0.5, 1 wt.%)Ag Alloys

Biodegradable Zn-0.05Mg-(0.5, 1 wt.%) Ag alloy was manufactured by indirectly extruding the alloy ingot at 200 °C with an extrusion ratio of 16:1. Dynamic recrystallization took place during the extrusion process, leading to the formation of equiaxed crystals with twins in both cross-sectional and longitudinal direction. There was no detectable Ag-related phase present except the Mg{sub 2}Zn{sub 11} in the alloys. Tensile strength was increased with an increase in Ag content, reaching 202 MPa when Ag content is 1 wt.%. As-extruded Zn-0.05Mg-0.5Ag showed better corrosion performance with a low corrosion current density of 2.2 A/cm{sup 2} and low corrosion rate of 0.15 mm/year. The antibacterial property improved for both Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) by addition of Ag. The antibacterial rates were more than 99% when Ag content is up to 1 wt.%. The biodegradable Zn-Mg-Ag alloys with high antibacterial behavior show great potential in medical devices.

36 MATERIALS SCIENCE↗