Publications

Abstract not provided.

AISI 316 austenitic stainless steel is a preferred material of construction for valves, fittings, and other fluid system components for high-pressure gaseous hydrogen service. The interaction of hydrogen with stainless steel depends on the prevailing stress-state and the microstructural characteristics of a component's material of construction, among other variables. To evaluate the effects of geometrical stress-risers and two-phase microstructures on hydrogen-assisted fracture of AISI 316 stainless steel, smooth and notched tensile properties were measured for annealed material as well as for autogenously welded specimens after thermal precharging with hydrogen. The tensile ductility of welded microstructures is significantly reduced by hydrogen precharging, and the addition of a notch further degrades ductility. These observations are rationalized in terms of hydrogen-enhanced localized plasticity. Copyright © 2009 ASM International® All rights reserved.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Non-destructive detection methods can reliably certify that gas transfer system (GTS) reservoirs do not have cracks larger than 5%-10% of the wall thickness. To determine the acceptability of a reservoir design, analysis must show that short cracks will not adversely affect the reservoir behavior. This is commonly done via calculation of the J-Integral, which represents the energetic driving force acting to propagate an existing crack in a continuous medium. J is then compared against a material's fracture toughness (J{sub c}) to determine whether crack propagation will occur. While the quantification of the J-Integral is well established for long cracks, its validity for short cracks is uncertain. This report presents the results from a Sandia National Laboratories project to evaluate a methodology for performing J-Integral evaluations in conjunction with its finite element analysis capabilities. Simulations were performed to verify the operation of a post-processing code (J3D) and to assess the accuracy of this code and our analysis tools against companion fracture experiments for 2- and 3-dimensional geometry specimens. Evaluation is done for specimens composed of 21-6-9 stainless steel, some of which were exposed to a hydrogen environment, for both long and short cracks.

Applications requiring the containment and transportation of hydrogen gas at pressures greater than 70 MPa are anticipated in the evolving hydrogen economy infrastructure. Since hydrogen is known to alter the mechanical properties of materials, data are needed to guide the selection of materials for structural components. The objective of this study is to characterize the role of yield strength, microstructural orientation, and small concentrations of ferrite on hydrogen-assisted fracture in two austenitic stainless steels: 21Cr-6Ni-9Mn (21-6-9) and 22Cr-13Ni-SMn (22-13-5). The testing methodology involves exposure of tensile specimens to high-pressure hydrogen gas at elevated temperature in order to precharge the specimens with hydrogen, and subsequently testing the specimens in laboratory air to measure strength and ductility. In all cases, the alloys remain ductile despite precharging to hydrogen concentrations of ∼1 at. %, as demonstrated by reduction in area values between 30% and 60% and fracture modes dominated by microvoid processes. Low concentrations of ferrite and moderate increases in yield strength do not exacerbate hydrogen-assisted fracture in 21-6-9 and 22-13-5, respectively. Microstructural orientation has a pronounced effect on ductility in 22-13-5 due to the presence of aligned second-phase particles. Copyright © 2008 by ASME.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.

Abstract not provided.