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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 1,369 records · Page 76
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Microstructure, Phase Transformation, Mechanical Behavior, Bio-corrosion and Antibacterial Properties of Ti-Nb-xSn (x = 0, 0.25, 0.5 and 1.5) SMAs

Porous Ti-Nb-xSn shape memory alloys (SMAs) are fabricated by microwave sintering technology. The microstructures exhibit needle-like morphologies, β{sub (N)} (normal straight and crossed needles along with needle-like morphology that resembles spaghetti or irregular lines with α-phases in between) as well as plate-like morphologies [normal straight plate-like morphology, α′′ and dendritic plate-like morphology, β{sub (D)}]. Increases in Sn addition significantly induce an increase in the density of the α-phase. XRD patterns exhibited three phases, namely the β-main phase with smaller intensities of α′′ and α. Further, the addition of 0.25% Sn led to more effective improvement in the intensity of the α′′-phase compared with 0.5% and 1.5% Sn addition. Additions of Sn also enhanced the fracture strength and its corresponding strain along with the shape memory effect (SME), where the best enhancement was achieved at 0.25% Sn. The corrosion rate (Ri) was reduced by rising Sn content, while both corrosion resistance and antibacterial zones were increased. The lower elastic modulus, as well as the robust mechanical properties and bioactivity, made these SMAs rather suitable for biomedical application purposes, where the low elastic modulus had value in terms of avoiding the problem of “stress shielding.”.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effects of Heat Treatment on Microstructure, Mechanical Properties, Corrosion Resistance and Cytotoxicity of ZM21 Magnesium Alloy as Biomaterials

The effects of heat treatment on microstructure, mechanical properties, corrosion resistance and cytotoxicity of extruded Mg-2Zn-1Mn (wt.%) alloy were investigated for biomedical application in this study. The extruded alloy was T4 treated at 510 °C for 4 h and T5 treated at 200 °C for 16 h separately. The extruded Mg-Zn-Mn alloy mainly consists of Mg{sub x}Mn{sub y} phases. After T4 treatment, the amount of Mg{sub x}Mn{sub y} phases decreases and average grain size rises from 8 to 24 μm. After T5 treatment, Mg{sub 7}Zn{sub 3} phase newly precipitates along the grain boundaries and the size of grain remains similar. Compared with the T4-treated samples, the extruded and T5-treated samples exhibit higher mechanical properties. The T5-treated samples have an ultimate tensile stress of 273 MPa and an elongation of 19.7%. On the other hand, T4-treated samples present higher corrosion resistance in electrochemical tests. The degradation rates of extruded, T4-treated and T5-treated samples are 0.44 mm/year, 0.48 mm/year and 0.50 mm/year, respectively, in Ringer’s solution at 37 ± 0.2 °C. In addition, T4-treated alloy does not induce toxicity to the L-929 cells in in vitro cytotoxicity test.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Optimization of Tensile and Corrosion Properties of Dissimilar Friction Stir Welded AA2024-7075 Joints

In this work, we performed some joining experiments of dissimilar aluminum alloys AA2024-T351 and AA7075-T651 using friction stir welding (FSW) technique with different process parameters (rotational speed, welding speed and plunge depth). Response surface methodology based on a central composite rotatable design was used to establish the mathematical models predicting the tensile properties and corrosion rate of dissimilar FSW joints with some high confidence level. Analysis of variance method was employed to verify the developed models. Besides, the influences of FSW process parameters on tensile and corrosion properties of joints were analyzed. In order to obtain a desirable combination property of the dissimilar FSW joints, the optimum process parameters after experimental verification were proposed as: rotational speed 1495 rev/min, welding speed 187 mm/min and plunge depth 0.03 mm. This verification illustrated that the developed models are appropriate for the modeling and optimization of process.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effects of Chloride and Carbonate on Corrosion of API-X100 Pipeline Steel

Effects of chloride, introduced with 0.03, 0.05, 0.10, 0.12, 0.22, 0.25 M, on the corrosion behavior of API-X100 pipeline steel in 0.15 M carbonate solutions were studied. The evaluations were carried out with monitoring the open-circuit potentials and electrochemical impedance spectroscopy (EIS). The open-circuit potentials gave an electrochemical evidence on the weakening opposite kinetics of the passive film formation to the kinetics of dissolution with higher chloride concentrations. The open-circuit potentials were less with higher chloride concentrations. The EIS tests indicated that the corrosion resistance decreased, and species diffusion increased with the chloride concentration, in multi-time constant interactions. In all tests, slippery transparent films formed with no presence of pitting on the sample surfaces.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Corrosion Investigation of Zinc–Aluminum Alloy (ZA-27) Matrix Reinforced with In Situ Synthesized Titanium Carbide Particle Composites

ZA-27 alloy matrix composites comprised of different volume fractions of TiC particles as reinforcement phase were synthesized by in situ technique. Microstructural, hardness and electrochemical analysis were performed on these samples along with the base ZA-27 alloy to assess any beneficial effect of making the composites over the base alloy. It was observed that hardness increases in composites as compared to the base alloy. However, hardness of the composite reduces on increasing the reinforcement percentage. Corrosion behavior was investigated by using Tafel and EIS plots in 3.5 wt.% NaCl solution at room temperature for all the samples. The results showed increase in corrosion resistance for composites than that of base alloy. However, ZA27 + 5%TiC composite showed better results as compared to that of ZA27 + 10%TiC composite. The decreased property of ZA27 + 10%TiC composite is because of the agglomeration of particles and also by the formation of galvanic cell.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Wear and Corrosive Behaviors of Electroless Ni-LaCl{sub 3} Composites on Nanoporous ATO Surface of Ti Substrate

Ti and its alloys, because of its poor wear and oxidation resistance, have seriously restricted its industrial applications in the dry friction conditions. Herein we reported an easy-handling and effective approach for electroless Ni-LaCl{sub 3} nanocomposite films on nanoporous ATO surface of Ti substrate to modify its surface properties. Anodized titanium oxide, shorted as ATO, was designed as a template to deposit Ni-LaCl{sub 3} films on Ti surface with superior bonding interface. By adjusting the anodizing voltage from DC 60 to 240 V, the surface of ATO templates was manipulated to achieve a suitable diameter of nanopores using high voltage with low-current density state. The as-received Ni-LaCl{sub 3} film with a leaflike surface was successfully formed on to ATO surface. With an increase in LaCl{sub 3} addition from 0 to 4.0 g L{sup −1} in bath, results indicated that the diversified orientations of Ni crystals along Ni (111), (200), (220) and (311) were detected for Ni-LaCl{sub 3} films, rather than preferred directions of Ni (111) and (200) for pure Ni sample. As expected, the specific wear rate was ~ 10{sup −5} mm{sup 3} (N m){sup −1} for Ni-4.0 g L{sup −1} LaCl{sub 3} films, which was two times lower than that of the un-coated Ti substrate. Besides a lower microhardness of ~ 629 HV{sub 0.2} was detected for pure Ni, which was much lower that of ~ 752 HV{sub 0.2} for Ni-LaCl{sub 3} films, but higher than that of ~ 336 HV{sub 0.2} for Ti substrate. In addition, a superior corrosion resistance was obtained for Ni-LaCl{sub 3} composites relative to pure Ni, which was ascribed to the coexistence of La{sup 3+} ions and its La-rich insoluble products on its corroded surfaces for completing the pitting holes. In view of these, the as-deposited Ni-LaCl{sub 3} films on the surface of Ti substrate could guide an available proposal for surface modifying of Ti alloys against the wear corrosive failures, further intensifying their servicing life as subjected to harsh conditions.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Influence of Substrate Bias Voltage on Corrosion and Wear Behavior of Physical Vapor Deposition CrN Coatings

The objective of the present paper is to study the influence of the substrate bias voltage on the microstructure, composition, deposition rate, tribological and corrosion properties of CrN coatings obtained by DC magnetron sputtering on 90CrMoV8 steel and Si (100) substrates. The substrate bias voltage varied from 0 to − 700 V. The deposited films were characterized by SEM, XRD and potentiodynamic polarization. The wear behavior and coefficient of friction were determined and investigated after rotative tribometer tests. The results indicated that the substrate bias voltage considerably affected the intrinsic properties of the CrN films. Indeed, it significantly influenced the grain size and the root-mean-squared roughness which varied from 20 to 29 nm, and from 9 to 19 nm, respectively, when polarization changed from 0 to − 700 V. All the CrN coatings have a dense columnar structure and are well crystallized according to the XRD analyses. Nevertheless, it has been shown that the peaks intensity decreased by increasing the substrate bias voltage. By applying a substrate bias voltage, it was obvious that the friction behavior was enhanced, and the wear volume was decreased. Finally, the CrN coating obtained under a substrate bias voltage of − 500 V presented the best corrosion resistance and wear resistance probably due to its dense microstructure.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effects of Heat Input on Weld-Bead Geometry, Surface Chemical Composition, Corrosion Behavior and Thermal Properties of Fiber Laser-Welded Nitinol Shape Memory Alloy

Bead-on-plate laser welding was carried out on 1-mm-thick Nitinol sheets at different heat input values. The variations in weld-bead geometry and variations in microstructures across the bead were studied. The effects of heat input on surface layer composition of the welded samples, corrosion properties and phase transformation temperature were examined. From x-ray photoelectron spectroscopy (XPS), it was clear that relative intensity of elemental Ni peak was higher in parent material and the oxidation state of Ti was Ti{sup 4+}. It was further observed from Auger electron spectroscopy (AES) that the Ti to Ni ratio on the top surface of the welded samples was more than 1, and as a result of this the stability of TiO{sub 2} layer was enhanced, which eventually helped to improve the corrosion property of the welded samples. The polarization resistance of the welded samples was increased by more than ten times compared to that of the un-welded samples. From differential scanning calorimetry (DSC), it became evident that phase transformation temperatures got changed due to welding.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of ECAP Die Angles on Microstructure Mechanical Properties and Corrosion Behavior of AZ80 Mg Alloy

In this article, the effect of channel angles on material properties was investigated during equal channel angular pressing of AZ80 magnesium alloy using processing route R at 325 °C processing temperature. Channel angles of 90° and 110° and common corner angle 30° have been considered for this study. It has been revealed that the channel angle has a significant influence on deformation homogeneity, microhardness, ultimate tensile strength, ductility and corrosion behavior of Mg alloys. Investigation with reference to as-received AZ80 Mg alloy indicates 18.47% improvement in UTS and 76.07% enhancement in ductility after processing through 3P-90° and 2P-110° ECAP, respectively. Also, the corrosion rate reduces to 89.47% after processing the sample with 3P-110° ECAP die.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Wear and Corrosion Resistances of Active Screen Plasma-Nitrided Duplex Stainless Steels

Two grades of duplex stainless steel, SAF 2205 and SAF 2507, were nitrided using an active screen plasma process carried out at 380 °C for 10 h and were characterized in terms of microstructure and hardness. Wear resistance was assessed by means of linear scratch tests, using loads below and above the critical load. Potentiodynamic polarization was used to analyze corrosion behavior in 0.6 M NaCl solution. X-ray diffractometry showed expanded austenite formation in all nitrided samples. The super duplex steel SAF 2507 showed much better scratch resistance, with low friction coefficient and greater toughness, as judged by the pattern of superficial cracks when it was tested above the critical load. The corrosion behavior of steels was also different, mainly in the active region, and nitriding had a more beneficial effect upon SAF 2507. The potential relative to the transpassive region was practically unaffected by the nitriding.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Corrosion and Tribocorrosion Behavior of Ti-B{sub 4}C Composites Joined with TiCuNi Brazing Alloy

Corrosion behavior of joined Ti-B{sub 4}C composites was evaluated in 9 g/L NaCl solution using cyclic polarization and electrochemical impedance spectroscopy. Tribocorrosion behavior was investigated by sliding against an alumina ball under open-circuit potential and potentiodynamic polarization. The results showed that joining did not negatively affect the corrosion behavior of the composites. Regarding tribocorrosion, while joining did not significantly influence the coefficient of friction and total wear volume loss, it resulted in slightly increased electrochemical activity under sliding. These results showed that brazing may be considered as a simple and low-cost technique for joining Ti-B{sub 4}C composites to be operated in tribocorrosive environments.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Y{sub 2}O{sub 3} Addition on the Microstructure, Wear Resistance, and Corrosion Behavior of W-4.9Ni-2.1Fe Heavy Alloy

Binding and particle phases are the two important parameters influencing materials properties. In this study, a series of novel W-4.9Ni-2.1Fe-xY{sub 2}O{sub 3} (in weight%) alloys with different Y{sub 2}O{sub 3} contents are prepared by secondary ball milling and spark plasma sintering (SPS) techniques to obtain uniformly distributed γ-(Ni, Fe) binding phases and finer grains. The microstructure, mechanical, wear resistance, and corrosion behavior of the sintered bodies with different Y{sub 2}O{sub 3} were obtained by x-ray diffraction, scanning electron microscopy, Rockwell hardness tester, friction wear tester, and three-dimensional profile instruments. The results showed that a certain addition of Y{sub 2}O{sub 3} led to refined grains and uniformed microstructures; but, if excessive, a weak grain refinement would be appeared. Moreover, the grain size tends to be stable with enhancing of the Y{sub 2}O{sub 3} content. Considering properties such as density, hardness, compression yield strength, grain size, and uniform distribution of tungsten hard phase and γ-(Ni, Fe) binding phase, the comprehensive optimal amount of 0.7 wt.% of Y{sub 2}O{sub 3} was attained for the alloy. Meanwhile, the SPS sintered body also exhibited the best friction, wear behavior, and corrosion resistance in 3.5% of NaCl solution.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Friction Stir Processing on the Microhardness, Wear and Corrosion Behavior of Al6061 and Al6061/SiO{sub 2} Nanocomposites

An effect of the friction stir processing (FSP), its pass numbers and addition of the SiO{sub 2} nanoparticles on microhardness, wear behavior and corrosion performance of the Al6061 aluminum alloy was investigated. Scanning electron microscopy (SEM) and optical microscopy were utilized to characterize the microstructure of the alloy, FSPed and composite samples. SEM observations revealed that the SiO{sub 2} particles were not uniformly dispersed in the matrix after two passes of FSP. However, increasing the pass number more than two passes resulted in a great improvement in the distribution of the SiO{sub 2} particles. The application of FSP led to overall softening compared to the base metal. Softening of the Al6061 alloy was probably attributed to the coarsening of Mg{sub 2}Si. Corrosion resistance of the FSPed samples found a significant reduction compared to the base metal. Applying higher pass number of the process and also addition of the SiO{sub 2} nanoparticles improved the wear behavior of the samples.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Electrochemical Frequency Modulation, Electrochemical Noise, and Atomic Force Microscopy Studies on Corrosion Inhibition Behavior of Benzothiazolone for Steel API X100 in 10% HCl Solution

In this work, electrochemical and surface techniques were applied to study the corrosion inhibition effects of benzothiazolone. 10% HCl was used to simulate the oil and gas well-acidizing fluid. Electrochemical frequency modulation and potentiodynamic polarization indicated that this material has excellent inhibiting features in very low concentrations. The influence of DC trend on electrochemical noise data was evaluated by polynomial fitting, and the optimum polynomial order m = 4 was obtained. After detrending, the charge of corrosion reaction obtained by electrochemical noise decreased with increasing inhibitor concentrations. In addition, the inhibition efficiencies from electrochemical noise were in agreement with data obtained by other electrochemical methods. Surface studies illustrated that the corroded surface was smoother in the presence of benzothiazolone. Electrochemical impedance and noise showed that benzothiazolone blocked the electrode surface by adsorption obeying Langmuir isotherm. According to quantum calculation, S atom in benzothiazolone indicated more tendencies for electrophilic attack in adsorption process. The main reason for high inhibition efficiencies in very low concentrations was the planar and simplicity of inhibitor structure which led to increasing the efficiency of adsorption by functional group especially sulfur.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Microstructure Evolution, Structural Integrity, and Hot Corrosion Performance of Nitrogen-Enhanced Stainless Steel Welds

This work articulated the multi-pass, gas tungsten arc welding by adopting pulsating current for joining nitrogen-enhanced, low-carbon austenitic stainless steel, AISI 316L(N). An austeno-ferrite stainless steel (ER2594) and an over-alloyed (ERNiCrMo-3) fillers were employed to join 6-mm-thick plates of AISI 316L(N). Acicular and lathy ferrite in the weld zone of ER2594 and the occurrence of secondary phases in the fusion zone of over-alloyed filler were observed. The notch tensile strength data attested that the joint strength was greater for the welds employing an over-alloyed filler. This study also affirms that the welds obtained with ER2594 filler resulted in better impact toughness (144 J) compared with ERNiCrMo-3 filler and base metal. Also the notch impact toughness of ER2594 weldment is increased to 60% in comparison with that of candidate metal. Corrosion studies were also performed by exposing the coupons in a eutectic salt mixture comprising of 40%K{sub 2}SO{sub 4}-60%NaCl for 50 cycles at 650 °C. It is observed that the weld zone employing over-alloyed filler experienced better high-temperature corrosion resistance compared to the base metal. The specific results of this investigation will be of greater demand to the nuclear and marine applications utilizing these joints.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Enhancement of Wear and Corrosion Resistance in Medium Carbon Steel by Plasma Electrolytic Nitriding and Polishing

The effect of plasma electrolytic polishing on the characteristics of medium carbon steel after anodic nitriding in a nitrate–chloride electrolyte was investigated. The structure, morphology, and phase composition of the layers were studied using an x-ray diffractometer and a metallographic microscope. Nitrided and polished specimens were tested under dry friction conditions with a counter-body made of bearing steel. Corrosion studies were performed using potentiodynamic polarization curves in 3% sodium chloride solution. Nitriding in a nitrate–chloride electrolyte was determined to increase the surface hardness up to 1040 HV due to the formation of a nitride–martensite layer with an outer oxide layer. After polishing of the nitrided surface, the loose outer part of the oxide layer containing microcracks and pores was removed. The reduction in the corrosion current density of 2.27 times of nitrided steel by plasma polishing without changing the structure of the diffusion layers was shown. The wear rate of the samples decreased from 560 μg/(N m) for untreated steel to 60 μg/(N m) as a result of nitriding and dropped to 8 μg/(N m) after plasma electrolytic polishing.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Effect of Boron Micro-alloying on Microstructure and Corrosion Behavior of Dual-Phase Steel

The present work aims to understand the effect of boron (B) as a micro-alloying element on the mechanical properties and corrosion behavior of a dual-phase steel that was prepared from boron-added steel via hot rolling. The ‘B’ micro-alloying increased the volume fraction of martensite from ~ 25 to 50% and improved the hardenability as compared to unalloyed DP steel subjected to similar rolling and heat treatment conditions. The yield strength, tensile strength and corrosion resistance of boron-added DP steel significantly improved from 405 to 690 MPa, 632 to 890 MPa and 0.125 to 0.110 mm/year, respectively, as compared to the unalloyed DP steel.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Porous Microcapsule-Based Regenerating Superhydrophobic Coating on 304L SS and Its Corrosion Properties

We report fabrication of a regenerating superhydrophobic coating on 304L stainless steels, with superior corrosion resistance, using porous microcapsules made of calcium hydroxide as a core and a polymeric shell consisting of ethyl cellulose and poly methyl methacrylate. The synthesized microcapsules are characterized using optical, atomic force and scanning electron microscopic techniques, x-ray diffraction, Fourier transform infrared spectroscopy and immersion tests. The diameter of porous and permeable microcapsules ranges from 2 to 20 μm. On immersion of the coated surface in sodium stearate solution, the calcium hydroxide from the core diffuses through the pores of microcapsules and forms nanocrystalline hydrophobic calcium stearate needles pointing outward that repel water molecules. The maximum water contact angle obtained was 155.7° ± 2.05°. The micro-nanoscale roughness of the surface was evident from the AFM measurement. The cross-hatch tape adhesion test confirmed the strong adherence of the superhydrophobic coating. On damage of the superhydrophobic coating, the regeneration is achieved by immersing it in sodium stearate solution for 6 h where a 10° increase in contact angle is observed. Electrochemical studies in 0.1 M NaCl showed significant decrease in the passive current density and a delayed pitting, confirming better corrosion resistance of the coating in chloride environment.

36 MATERIALS SCIENCE↗