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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Effect of heat input on dissimilar welds of ultra high strength steel and duplex stainless steel: Microstructural and compositional analysis

The effect of heat input on the microstructure and compositional heterogeneity of welds of direct-quenched ultra high strength steel (Optim 960 QC) and duplex stainless steel (UNS S32205) was studied. The dissimilar welds were made using GMAW with a fully austenitic filler wire. In addition to grain coarsening in the heat affected zone (HAZ) of the ferritic side, it was found that an increase in heat input correlatively increased the proportional volume of bainitic to martensitic phases. Coarse ferritic grains were observed in the duplex HAZ. Higher heat input, however, had a beneficial effect on the nucleation of austenite in the HAZ. Heat input had a regulatory effect on grain growth within the austenitic weld and more favorable equiaxed austenite was obtained with higher heat input. On the ferritic side of the welds, macrosegregation in the form of a martensitic intermediate zone was observed for all the cooling rates studied. However, on the duplex side, macrosegregation in the fusion boundary was only noticed with higher cooling rates. Microstructural observations and compositional analysis suggest that higher heat input could be beneficial for the structural integrity of the weld despite higher heat input increasing the extent of adverse coarse grains in the HAZ, especially on the ferritic side. - Highlights: •The effect of heat input on dissimilar welds of UHSS and DSS was studied. •Transmutation of the microstructure was discussed in detail. •The influence of heat input on compositional heterogeneity of welds was described. •Higher heat input enhanced bainitic transformation on the ferritic side. •Macrosegregation was affected by the amount of heat input on the DSS side.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Low Cost Hydrogen Storage at 875 Bar Using Steel Liners and Steel Wire Wraps

The Department of Energy’s (DOE) Fuel Cell Technologies Office (FCTO) within the Office of Energy Efficiency and Renewable Energy (EERE) supports research and development activities leading to the development of low-cost, high-pressure hydrogen storage systems for use in hydrogen refueling stations (forecourt). The specific goals of this project were to develop and produce a prototype of a pressure vessel to safely store gaseous hydrogen at 875 bar that meets the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Section VIII, Division 3 design code for service in hydrogen (Article KD-10) and meets the DOE storage tank cost target of <$1000/kg stored hydrogen (H 2 ). The pressure vessel designed and prototyped as part of this study utilizes a standard ASME approved, 406 mm diameter, 31.7 mm thick wall, and 9.14m long, liner with a capacity of 765 liters and rated for a pressure of up to 460 bar. The liner was wrapped with high strength steel wires to boost its pressure rating to 875 bars. The process of wrapping metal liners with a high strength steel wire, a WireTough patented technology, was first demonstrated on short cylinders that were 1.9 m long but of the same diameter and wall thickness as the 9.1 m long, 765 L cylinders. Subsequently, full length cylinders that were 9.14 m long were designed and certified under the applicable ASME Design Codes. Two prototype cylinders were wire wrapped to demonstrate the manufacturability. Following is a bulleted summary of the accomplishments of the project that ended on August 31, 2018.

25 ENERGY STORAGE↗
DOE OSTI2020

Effect of nickel on the kinematic stability of retained austenite in carburized bearing steels – In-situ neutron diffraction and crystal plasticity modeling of uniaxial tension tests in AISI 8620, 4320 and 3310 steels

The presence of kinematically metastable retained austenite in the microstructure of bearing components can significantly affect the macro and micro-mechanical material response. In the present work, the influence of Ni on the stability of the retained austenite within three different grades of high carbon bearing steel using in-situ neutron diffraction is investigated. For the first time, the results show that presence of Ni increases the stability of the austenite in the elastic regime whereas the transformation rate remains unaffected. Crystal plasticity finite element (CPFE) modeling was used to study the deformation in these three steels and shows that the predominant factor causing the difference in mechanical behavior of these steels is the austenite stability. Finally, the elastic and plastic response of the matrix martensite was found to be identical among all specimens while the austenite demonstrates similar elastic behavior but remarkably different stabilities under monotonic loading.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Friction Stir Dovetailing of AA7099 to Steel with AA6061 Interlayer for Reduced Zn Embrittlement at Dissimilar Interface

Joining of high strength Al alloy (AA7099) to steel (rolled homogeneous armor) with and without AA6061 interlayer was achieved using a friction stir dovetailing (FSD) method. Detailed investigations were conducted to establish correlations between mechanical performance and microstructural evolution of FSD joints. Lap shear tensile testing revealed that incorporation of the AA6061 interlayer combined with tailored processing methodology significantly improved both mechanical interlocking and load transmission across the dovetail interface. Following incorporation of the interlayer, the maximum load carrying capacity and peak extension (of the AA7099/AA6061/steel joint) are 60% and 210% higher, respectively, than results obtained from an AA7099/steel joint without an interlayer. Without an AA6061 interlayer, formation of zinc rich intermetallic compounds led to brittle interfacial failure of the AA7099-steel FSD joint. Incorporation of novel tool and joint configuration eliminated asymmetric joint performance as a function of loading direction, which is generally observed in friction stir lap welding. The efficacy of the use of an AA6061 interlayer in joining AA7099 to steel was demonstrated through mechanical testing as well as high resolution analytical electron microscopy characterization.

Dissimilar metal joining, Friction stir dovetailin↗
DOE OSTI2013

Recent Progress of R&D Activities on Reduced Activation Ferritic/Martensitic Steels

Several types of reduced activation ferritic/martensitic (RAFM) steel have been developed over the past 30 years in China, Europe, India, Japan, Russia and the USA for application in ITER TBM and future fusion DEMO and power reactors. The progress has been particularly important during the past few years with evaluation of mechanical porperties of these steels before and after irradiation and in contact with different cooling media. This paper presents recent RAFM steel results obtained in ITER partner countries in relation with different TBM and DEMO options

Huang, Q.↗
DOE OSTI2018

Effects of long-term thermal aging on bulk and local mechanical behavior of ferritic-austenitic duplex stainless steels

Ferritic-austenitic duplex stainless steels (DSS) undergo significant thermal aging embrittlement in service in light water reactors. Specimens of cast CF–3 and CF–8 DSS have been laboratory aged for up to 17,200 h at four different temperatures (280, 320, 360, 400 °C) in order to characterize the aging evolution and mechanical properties. Standard Charpy V-Notch (CVN) impact testing and tensile testing are employed to measure the progression of embrittlement of the steels. Concurrently, nanoindentation measurements are performed to measure the hardening of the individual ferrite and austenite phases. Atom probe tomography (APT) analysis of the ferrite and austenite phases elucidates the relationship between spinodal decomposition of the ferrite and the mechanical effects of aging. The results are discussed to relate the effects of the local microstructure and property changes in the ferrite phase on the overall bulk mechanical evolution of these steels.

Schwarm, Samuel C.↗
DOE OSTI2022

Towards directed energy deposition of metals using polymer-based supports: porosity of 316L stainless steel deposited on carbon-fiber-reinforced ABS

Directed energy deposition (DED) is increasingly valuable to many industries because of its high deposition rates relative to other metal additive manufacturing processes, but the design space of DED is limited. For instance, steep overhangs are difficult or impossible to manufacture. Polymer-based support structures could help address this challenge. The viability of DED on polymer composite substrates has begun to be explored, specifically with 316L stainless steel on carbon-fiber-reinforced ABS substrates. Monolithic metal components can be deposited on the polymer, but it was found that gas release during polymer degradation causes porosity due to gas entrapment in the metal. An interlayer cooling time was introduced to reduce polymer degradation and decrease the porosity due to gas entrapment, but this led to porosity from lack of fusion. The results of this work provide insight into process parameter selection and scan strategy development to enable the use of polymer support structures in blown-powder DED.

Kurfess, Rebecca↗
DOE OSTI2019

Graphite Steel and Chromium-Nickel Steel Corrosion: Solution Flow Through Corrosion Experiments

The corrosion of steel, when exposed to various compositions of brines is a complex, heterogeneous process involving dissolution and precipitation of multiple solids. The rate at which elements will be released from the corrosion process under these conditions will depend, in part, on effects associated with secondary alteration phases (passivating film) that may potentially form under these conditions. Understanding these processes has required the development of sophisticated methods to sample and quantitatively characterize the composition of the steel as it corrodes and releases elements. The determination of the concentrations of both brine and steel corrosion components in solutions sampled from these tests is required to fully understand the process that may eventually lead to dissolution of corrosion products.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

3% Silicon Steel Core Material (Grain Oriented Electrical Steel) (Rev.01)

3% (Grain-Oriented) Silicon Steel is a soft magnetic material that is best used in electrical power transformers and inductors. It has a silicon content up to 3.2 mass %, which increases the electrical resistivity and reduces eddy current losses. The magnetic properties can be enhanced during a cold rolling stage (along the length) to produce textured sheets, known as grain-oriented electrical steel. Due to its preferred crystallographic orientation, it is used primarily for non-rotating applications, i.e. transformers and inductors. Typical operating frequency of 3% Silicon Steel is 50-60 Hz (hertz). A variety of forms can be manufactured, including lamination, toroidal and C-cores, as well as glued block cores of various shapes by cutting or pressing.

36 MATERIALS SCIENCE↗
NASA NTRS1973

Gas-phase hydrogen permeation through alpha iron, 4130 steel, and 304 stainless steel from less than 100 C to near 600 C

Gas phase hydrogen permeation studies were conducted on hollow, cylindrical membranes of triply zone-refined alpha iron, AISI 304 austenitic stainless steel, and AISI-SAE 4130 steel in both the normalized (ferrite and carbide) and quenched and tempered (martensite) conditions. Membrane temperature was varied from less than 100 C to near 600 C and hydrogen pressure was varied. For one membrane material, normalized 4130 steel, gas phase hydrogen transport under both steady state and nonsteady state conditions was demonstrated to be controlled by lattice diffusion. Additionally, Sievert's law was shown to be applicable. For all membrane materials, expressions for the coefficients for hydrogen permeation were determined by analysis of steady state transport; the coefficients for diffusion were determined by the lag time technique applied to nonsteady state transport; and through a knowledge of the Sievert's constants, the subsurface equilibrium lattice hydrogen concentrations were determined.

Nelson, H. G.↗
NASA NTRS1978

Influence of fretting on flexural fatigue of 304 stainless steel and mild steel

Fretting fatigue experiments conducted on 304 stainless steel using a flexural fatigue test arrangement with bolted on fretting pads demonstrated that fatigue life is reduced by at least a factor of 10 in the 265 to 334 MPa (38,500 - to 48,500 psi) nominal flexural fatigue stress range. In addition, experiments in which the fretting pads were removed after selected numbers of cycles, followed by continued flexural fatigue without fretting show that continued fretting beyond 50,000 cycles does not significantly further reduce fatigue life of 304 stainless steel at 317 MPa (46,000 psi). Microscopic examination of the fretted contact areas revealed fracture initiation sites as well as numerous cracks that did not propagate to failure. Flexural fretting fatigue experiments performed on mild steel showed an insensitivity of fatigue life to the incidence of fretting under flexural stress conditions of from 162 to 217 MPa (23,500 to 31,500 psi).

Bill, R. C.↗
NASA NTRS1979

Study of austenitic stainless steel welded with low alloy steel filler metal

The tensile and impact strength properties of 316L stainless steel plate welded with low alloy steel filler metal were determined. Tests were conducted at room temperature and -100 F on standard test specimens machined from as-welded panels of various chemical compositions. No significant differences were found as the result of variations in percentage chemical composition on the impact and tensile test results. The weldments containing lower chromium and nickel as the result of dilution of parent metal from the use of the low alloy steel filler metal corroded more severely in a marine environment. The use of a protective finish, i.e., a nitrile-based paint containing aluminum powder, prevented the corrosive attack.

Burns, F. A.↗
DOE OSTI2017

Mechanical property degradation and microstructural evolution of cast austenitic stainless steels under short-term thermal aging

Mechanical testing and microstructural characterization were performed on short-term thermally aged cast austenitic stainless steels (CASS) to understand the severity and mechanisms of thermal-aging degradation experienced during extended operation of light water reactor (LWR) coolant systems. Four CASS materials – CF3, CF3M, CF8, and CF8M – were thermally aged for 1500 hours at 290 °C, 330 °C, 360 °C, and 400 °C. All four alloys experienced insignificant change in strength and ductility properties but a significant reduction in absorbed impact energy. The primary microstructural and compositional changes during thermal aging were spinodal decomposition of the δ-ferrite into α/ α`, precipitation of G-phase in the δ-ferrite, segregation of solute to the austenite/ ferrite interphase boundary, and growth of M23C6 carbides on the austenite/ferrite interphase boundary. These changes were shown to be highly dependent on chemical composition, particularly the concentration of C and Mo, and aging temperature. A comprehensive model is being developed to correlate the microstructural evolution with mechanical behavior and simulation for predictive evaluations of LWR coolant system components.

36 MATERIALS SCIENCE↗
DOE OSTI2023

SA508 low alloy steel to 316L stainless steel dissimilar metal joint made by powder metallurgy hot isostatic pressing

Joining ferritic SA508 low alloy steel (LAS) and austenitic 316 L stainless steel (SS) via powder metallurgy hot isostatic pressing (PM-HIP) was evaluated as an alternative method to welding. This study investigated the mechanical and microstructural evolutions of the bimetallic interface under different joint designs and heat treatments. Here, the direct joining of dissimilar metal alloys by PM-HIP method resulted in two designs: 1) powder SA508 to solid bar 316 L (P508–B316L) and 2) powder 316 L solid bar SA508 (P316L-B508). In both cases, P508–B316L and P316L-demonstrated satisfactory tensile strength, however, high hardness and severe depreciation in toughness were located on the bimetallic interface. The mechanisms responsible for the detrimental mechanical properties were verified. Large oxides were observed in P508–B316L due to the prior powder boundary (PPB) oxides present in SA508 powder. The intense sensitization occurred from the formation of M 23 C 6 carbides, consequently from the slow cooling after PM-HIP in P316L-B508. Post-HIP heat treatments were explored to reduce the distance of carbide formation; however, the heat treatment could not eliminate the carbides. The experimental results were compared to the diffusion couple simulation as a function of carbide formation with distance. The analysis also showed the high hardness at the bimetallic interface was primarily contributed by solid solution strengthening. In conclusion, the direct joining of P316L-B508 and P508–B316L via PM-HIP was deemed to be unfeasible, and a transitional material is necessary to impede the diffusion of carbon.

316L stainless Steel↗
DOE OSTI2013

Heavy reflector experiments in the IPEN/MB-01 reactor: Stainless steel, carbon steel and nickel

New experiments devoted to the measurements of physical parameters of a light water core surrounded by a heavy reflector were performed in the IPEN/MB-01 research reactor facility. These experiments comprise three sets of heavy reflector (SS-304, Carbon Steel, and Nickel) in a form of laminates around 3 mm thick. Each set was introduced individually in the west face of the core of the IPEN/MB-01 reactor. The aim here is to provide high quality experimental data for the interpretation and validation of the SS-304 heavy reflector calculation methods. The experiments of Carbon Steel, which is composed mainly of iron, and Nickel were performed to provide a consistent and an interpretative check for the SS-304 reflector experiment. The experimental results comprise critical control bank positions, temperatures and reactivities as a function of the number of the plates. Particularly to the case of Nickel, the experimental data are unique of its kind. The theoretical analysis was performed by MCNP-5 with the nuclear data library ENDF/B-VII.0. It was shown that this nuclear data library has a very good performance up to thirteen plates and overestimates the reactivity for higher number of plates independently of the type of the reflector.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2017

Irradiation Accelerated Corrosion of Stainless Steel and Ferritic-Martensitic Steel in Simulated Primary Water

Austenitic stainless steel, and ferritic-martensitic steel were irradiated with a proton beam while simultaneously exposed to simulated PWR primary water. Samples were exposed for 4-72 hr in 320°C water with 3 wppm hydrogen while simultaneously irradiated at surface dose rates from 400-4000 kGy/s (4x10-7 to 7x10-6 dpa/s). After exposure, samples were characterized with TEM, EDS, and Raman spectroscopy to determine the effects of radiation on the growth and stability of the oxide films. Samples which were irradiated during exposure had thinner inner oxides compared to unirradiated samples. Irradiated samples also had hematite on their surfaces, while unirradiated samples did not, indicating an increase in corrosion potential due to irradiation. Sample regions which were not irradiated but were exposed to the flow of irradiated water were similar to directly irradiated regions, suggesting that water radiolysis is the mechanism primarily responsible for the observed effects.

Stainless Steel, ferritic-martensitic steel, radia↗