EFFECTS OF EXTREME HYDROGEN ENVIRONMENTS ON THE FRACTURE AND FATIGUE BEHAVIOR OF ADDITIVELY MANUFACTURED STAINLESS STEELS.
Abstract not provided.
Smith, Thale↗
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A Comparative Evaluation of Additive Manufactured Stainless Steel Test Pieces
Stainless steel is used for variety of applications with different grades, alloys, filaments and powders. Additive manufacturing (AM) enables unique design features and refined microstructures. Performance testing on AM parts are needed as input to modeling and accelerated qualification processes. The objective of this work is to determine the effect of surface roughness on corrosion rate for from different manufacturers Preliminary evaluation shows that the 500-hour data set was scattered, and trend analysis are complex, while the 1000h and 1500h test results evaluation show more distinct trends.
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
Structural representation of additively manufactured 316L austenitic stainless steel
Three 316L stainless steel materials are studied and reported upon; wrought, as-built additively manufactured (AM), and heat-treated AM material. The AM material was produced from the laser engineered net shaping (LENS) process. Macroscopic uniaxial compression stress-strain curves were obtained for all three materials. The curves were similar for the wrought and heat-treated AM materials but the as-built AM material demonstrated approximately 1.7 times greater flow stress at any given level of strain than the other two materials. Electron-backscatter diffraction analysis of the materials also showed that the microstructures of the three materials differed; with complex grain morphology for the as-built AM material. The mean grain size of each of the three materials also differed. Furthermore, the initial dislocation density was also measured with neutron diffraction and line-profile analysis for both wrought and as-built AM materials with the density in the AM material approximately 2.5 times greater.
36 MATERIALS SCIENCE↗
High-pressure torsion assisted segregation and precipitation in a Fe-18Cr-8Ni austenitic stainless steel
Not provided.
Materials Science↗
TECHNICAL BACKGROUND FOR THE UPDATE AND EXTENSION OF THE TIME-DEPENDENT ALLOWABLE STRESSES OF TYPE 304H AND 316H STAINLESS STEELS
Type 304H and 316H stainless steels are codified in the ASME Boiler and Pressure Vessel Code for Section III, Division 5, Class A construction for up to 1500F (816C) and 300,000 hours. Extension of the design lifetimes to 500,000 hours has been undertaken by various research projects and by the ASME Section III, Division 5 Code Committees. Due to a long-standing issue related to non-classical creep behavior on the use of the time to the onset of tertiary creep as one of the time-dependent allowable stress criteria, little progress was made in the extension of the time-dependent allowable stresses for Type 304H and 316H stainless steels. A recent effort by Dabrow and Nestell (Impact of Tertiary Creep on Time Dependent Allowable Stresses for Type 304H and 316H Stainless Steels, Report 0300-0003-RPT-001, MPR Associates, Alexandria, VA, 2020) has provided a rational method for the treatment of the highly variable data for the time to onset of tertiary creep. In this paper, the background formulas for determining the time-dependent allowable stress values of Type 304H and 316H stainless steels, as assembled from relevant project work, are presented. These updates and extensions are being recommended to the ASME Code committees for approval, and are subject to change upon feedback from ASME Section III Code committees.
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
Communication—Reactive Sintering of a CoFe 2 O 4 Coating on Ferritic Stainless Steels for SOFC Interconnect Application
A mixed Fe+CoO precursor was successfully utilized to synthesize a dense CoFe 2 O 4 spinel coating on the Crofer 22 APU interconnect via reactive sintering at 900°C for 2 h in air without the use of any reduction treatment. Both the uncoated and coated samples were subject to thermal oxidation at 850°C for 500 h in air. Phase constituents, microstructure, and area specific resistance (ASR) of the uncoated and coated samples before and after the oxidation testing were evaluated. The CoFe 2 O 4 layer effectively reduced the Cr 2 O 3 scale growth and lowered the scale ASR.
25 ENERGY STORAGE↗
TECHNICAL BACKGROUND FOR THE UPDATE AND EXTENSION OF THE TIME-DEPENDENT ALLOWABLE STRESSES OF TYPE 304H AND 316H STAINLESS STEELS
Type 304H and 316H stainless steels are codified in the ASME Boiler and Pressure Vessel Code for Section III, Division 5, Class A construction for up to 1500F (816C) and 300,000 hours. Extension of the design lifetimes to 500,000 hours has been undertaken by various research projects and by the ASME Section III, Division 5 Code Committees. Due to a long-standing issue related to non-classical creep behavior on the use of the time to the onset of tertiary creep as one of the time-dependent allowable stress criteria, little progress was made in the extension of the time-dependent allowable stresses for Type 304H and 316H stainless steels. A recent effort by Dabrow and Nestell (Impact of Tertiary Creep on Time Dependent Allowable Stresses for Type 304H and 316H Stainless Steels, Report 0300-0003-RPT-001, MPR Associates, Alexandria, VA, 2020) has provided a rational method for the treatment of the highly variable data for the time to onset of tertiary creep. In this paper, the background formulas for determining the time-dependent allowable stress values of Type 304H and 316H stainless steels, as assembled from relevant project work, are presented. These updates and extensions are being recommended to the ASME Code committees for approval, and are subject to change upon feedback from ASME Section III Code committees.
304/316 life extension↗
Explosive fragmentation of additively manufactured stainless steel
Properties of fragmentation from an explosively driven 316L stainless steel spherical shell section fabricated by a laser powder bed additive manufacturing process with minimal surface finishing are investigated. This shell is driven by an insensitive high explosive, resulting in high strain rate deformation (>8 × 10 3 s –1 ) and failure of the stainless steel. Photonic Doppler velocimetry measures the expansion rate; dynamic radiography and high-speed imaging capture the fracture behavior of the stainless steel. The fracture response of the additively manufactured stainless steel shell is compared to published experimental results on additively manufactured 316L stainless steel and conventionally manufactured wrought 316L and 304 stainless steel shell fragmentation. Despite preferred crack orientation, suggesting the influence of surface grooves on fracture time, fragment size is identical to that measured in a similar experiment on wrought 304 stainless steel. Further analysis indicates that the 316L additively manufactured stainless steel shell exhibits comparable spall strength and fragmentation toughness to conventionally manufactured stainless steel yet lower failure strain due to surface stress concentrations.
36 MATERIALS SCIENCE↗
Low-chromium stainless steels
Two modified stainless-steel formulations, with only two-thirds chromium content found in conventional type 304, have mechanical and chemical properties comparable to type 304. Low-chromium stainless steels have potential uses in heat exchangers, transfer lines for chemicals, automobile trim, and other applications.
Barrett, C. A.↗
Tritium Effects on Mechanical Properties of Austenitic Stainless Steels
Why Austenitic Stainless Steel for Tritium Service? • High strength and ductility for structural components and pressure boundaries • Austenitic SS is highly resistant to hydrogen isotope embrittlement • Not immune though
Wieber, Natalile↗
Effects of Heat Treatment on Phase Transformation and Corrosion Resistance of Boride Layer on Austenitic Stainless Steel AISI 304
The austenitic stainless steel AISI 304 was thermochemically surface treated using a powder-packed boronizing process at a temperature of 950 °C for about 4 hours. Double-phase boride layer (FeB and Fe{sub 2}B) was detected and then investigated for the corrosion resistance compared with the untreated one. Heat treatment was performed at a temperature range of 800 to 900 °C for 2 hours on the boronized austenitic stainless steel AISI 304 to diminish the double-phase boride layer. Afterward, corrosion tests were performed to clarify the effects of heat treatment as well as phase transformation on the corrosion resistance of the boronized austenitic stainless steel AISI 304. The results of this study showed that the formation of single-phase Fe{sub 2}B layer offers the best corrosion resistance.
36 MATERIALS SCIENCE↗
Surface Processes Control the Fate of Reactive Oxidants Generated by Electrochemical Activation of Hydrogen Peroxide on Stainless-Steel Electrodes
Low-cost stainless-steel electrodes can activate hydrogen peroxide (H 2 O 2 ) by converting it into a hydroxyl radical ( • OH) and other reactive oxidants. At an applied potential of +0.020 V, the stainless-steel electrode produced • OH with a yield that was over an order of magnitude higher than that reported for other systems that employ iron oxides as catalysts under circumneutral pH conditions. Decreasing the applied potential at pH 8 and 9 enhanced the rate of H 2 O 2 loss by shifting the process to a reaction mechanism that resulted in the formation of an Fe(IV) species. Significant metal leaching was only observed under acidic pH conditions (i.e., at pH <6), with the release of dissolved Fe and Cr occurring as the thickness of the passivation layer decreased. Despite the relatively high yield of • OH production under circumneutral pH conditions, most of the oxidants were scavenged by the electrode surface when contaminant concentrations comparable to those expected in drinking water sources were tested. The stainless-steel electrode efficiently removed trace organic contaminants from an authentic surface water sample without contaminating the water with Fe and Cr. With further development, stainless-steel electrodes could provide a cost-effective alternative to other H 2 O 2 activation processes, such as those by ultraviolet light.
42 ENGINEERING↗
Crystallography of intergranular corrosion in sensitized austenitic stainless steel
Highlights: • Intergranular corrosion (IGC) in stainless steel was crystallographically discussed. • Grain boundaries (GBs) were classified based on the coincidence site lattice (CSL). • Influence of the Σ value on their IGC susceptibility had a wide range scatter. • IGC susceptibility was characterized by the Σ value and unit cell area of CSL GBs. - Abstract: This study deals with the susceptibility to intergranular corrosion (IGC) in type 304 austenitic stainless steel from a crystallographic viewpoint. An IGC test was conducted using oxalic acid and sensitized stainless steel, whose crystal orientation was analyzed by electron backscattered diffraction (EBSD). GBs were classified according to the misorientation of adjacent grains, and subclassified using the Σ value based on the coincidence site lattice (CSL) model. The width of corroded groove was measured for each GB category, and the effect of GB category on the susceptibility to IGC was examined. Then, the area of the unit cell of CSL boundaries was used to characterize the susceptibility to IGC of CSL boundaries. It was found that no IGC occurred in low-angle GBs with a misorientation of 15°, the width of corroded groove at each Σ boundary exhibited large scatter. The relationship between the width and unit cell area was characterized by a sigmoid curve, and the susceptibility to IGC was well described by the unit cell area.
36 MATERIALS SCIENCE↗