HYDROGEN EFFECTS ON FRACTURE TOUGHNESS OF TYPE 316L STAINLESS STEEL FROM 175 K TO 425 K. PDF Download
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Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
The effects of hydrogen on the fracture-toughness properties of Type 316L stainless steel from 175 K to 425 K were measured. Fracture-toughness samples were fabricated from Type 316L stainless steel forgings and hydrogen-charged with hydrogen at 34 MPa and 623 K for two weeks prior to testing. The effect of hydrogen on the J-Integral vs. crack extension behavior was measured at various temperatures by fracturing non-charged and hydrogen-charged samples in an environmental chamber. Hydrogen-charged steels had lower toughness values than non-charged ones, but still retained good toughness properties. The fracture-toughness values of hydrogen-charged samples tested near ambient temperature were about 70% of non-charged values. For hydrogen-charged samples tested at 225 K and 425 K, the fracture-toughness values were 50% of the non-charged values. In all cases, fracture occurred by microvoid nucleation and coalescence, although the hydrogen-charged samples had smaller and more closely spaced microvoids. The results suggest that hydrogen effects on toughness are greater at 225 K than they are at ambient temperature because of strain-induced martensite formation. At 425 K, the hydrogen effects on toughness are greater than they are at ambient temperature because of the higher mobility of hydrogen.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
The effects of hydrogen on the fracture-toughness properties of Type 316L stainless steel from 175 K to 425 K were measured. Fracture-toughness samples were fabricated from Type 316L stainless steel forgings and hydrogen-charged with hydrogen at 34 MPa and 623 K for two weeks prior to testing. The effect of hydrogen on the J-Integral vs. crack extension behavior was measured at various temperatures by fracturing non-charged and hydrogen-charged samples in an environmental chamber. Hydrogen-charged steels had lower toughness values than non-charged ones, but still retained good toughness properties. The fracture-toughness values of hydrogen-charged samples tested near ambient temperature were about 70% of non-charged values. For hydrogen-charged samples tested at 225 K and 425 K, the fracture-toughness values were 50% of the non-charged values. In all cases, fracture occurred by microvoid nucleation and coalescence, although the hydrogen-charged samples had smaller and more closely spaced microvoids. The results suggest that hydrogen effects on toughness are greater at 225 K than they are at ambient temperature because of strain-induced martensite formation. At 425 K, the hydrogen effects on toughness are greater than they are at ambient temperature because of the higher mobility of hydrogen.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
The effect of hydrogen on the fracture toughness properties of Types 304L, 316L and 21-6-9 forged stainless steels was investigated. Fracture toughness samples were fabricated from forward-extruded forgings. Samples were uniformly saturated with hydrogen after exposure to hydrogen gas at 34 MPa or 69 and 623 K prior to testing. The fracture toughness properties were characterized by measuring the J-R behavior at ambient temperature in air. The results show that the hydrogen-charged steels have fracture toughness values that were about 50-60% of the values measured for the unexposed steels. The reduction in fracture toughness was accompanied by a change in fracture appearance. Both uncharged and hydrogen-charged samples failed by microvoid nucleation and coalescence, but the fracture surfaces of the hydrogen-charged steels had smaller microvoids. Type 316L stainless steel had the highest fracture toughness properties and the greatest resistance to hydrogen degradation.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Fracture toughness (K/sub c/) of 17-4 PH stainless steel decreased significantly with increased hydrogen test pressure for a variety of heat treatment conditions: solution annealed, underaged, peak-aged, and overaged. Minimum toughness (13 MPa.sqrt.m) was obtained with peak-aged samples tested in 69.5-MPa hydrogen; toughness was maximum (100 MPa.sqrt.m) for samples tested in helium. Aging treatments increased the hardness from 28 R/sub c/ for solution-annealed material to 42 R/c/ for peak-aged material and correspondingly decreased the fracture toughness in high-pressure hydrogen (K/sub H/) from 31 to 13 MPa.sqrt.m. However, increased hardness had no substantial effect on the K/sub c/ in helium. Fracture mechanism changed from predominantly ductile rupture in helium to cleavage in 69.5-MPa hydrogen, with mixed-mode fractures at lower hydrogen pressure (3.5-MPa). On the basis of these data, 17-4 PH stainless steel is not recommended for hydrogen service.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
The deformation and fracture toughness properties of forged stainless steels pre-charged with tritium were compared to the deformation and fracture toughness properties of the same steels heat treated at 773 K or 873 K and precharged with hydrogen. Forged stainless steels pre-charged with tritium exhibit an aging effect: Fracture toughness values decrease with aging time after precharging because of the increase in concentration of helium from tritium decay. This study shows that forged stainless steels given a prior heat treatment and then pre-charged with hydrogen also exhibit an aging effect: Fracture toughness values decrease with increasing time at temperature. A microstructural analysis showed that the fracture toughness reduction in the heat-treated steels was due to patches of recrystallized grains that form within the forged matrix during the heat treatment. The combination of hydrogen and the patches of recrystallized grains resulted in more deformation twinning. Heavy deformation twinning on multiple slip planes was typical for the hydrogen-charged samples; whereas, in the non-charged samples, less twinning was observed and was generally limited to one slip plane. Similar effects occur in tritium pre-charged steels, but the deformation twinning is brought on by the hardening associated with decay helium bubbles in the microstructure.
Author: Publisher: ISBN: Category : Languages : en Pages : 15
Book Description
The effects of hydrogen on the fracture toughness properties of upset welded Type 304L stainless steel were measured and compared to those measured previously for as-received and as-welded steels. The results showed that the upset welded steels had good fracture toughness properties, but values were lower than the as-received material. The fracture toughness value of the base material was 6420 in-lbs/sq. in., while the welded steels averaged 3660 in-lbs/sq. in. Hydrogen exposure lowered the fracture toughness values of the as-received steel by 43 % to 3670 in-lbs/sq. in. and the welded steels by 21 % to 2890 in-lbs/sq. in. The fracture morphologies of the unexposed steels showed that ductile fracture occurred by the microvoid nucleation and growth process. The size of the microvoids on the fracture surfaces of the welded steels were much smaller and more closely spaced that those found on the base material fracture surfaces. The change in the size and spacing of the microvoids indicates that the fracture toughness properties of the welded steels were lower than the base steels because of the higher concentration of microscopic precipitates on the weld plane. The welds examined thus far have been {open_quotes}good{close_quotes} welds and the presence of these precipitates was not apparent in standard {open_quotes}low{close_quotes}-magnification metallographic sections of the weld planes. The results indicate that hydrogen did not weaken greatly the solid-state welds but that other inclusions or impurities present prior to welding did. Improvements in surface cleaning and preparation prior to welding should be explored as a way to improve the strength of solid-state welded joints.
Author: Ellis E. Fletcher Publisher: ISBN: Category : Steel Languages : en Pages : 82
Book Description
This report deals with the deleterious effects of hydrogen gas on steel at elevated temperatures and/or pressures. Hydrogen attack on steels is manifest as decarburization, intergranular fissuring, or blistering. These conditions result in lowered tensile strength, ductility, and impact strength. The reaction of hydrogen with iron carbide to form methane is probably the most important chemical reaction involved in the attack on steel by hydrogen. Attack of steel at elevated temperatures and pressures is limited or prevented by the following measures: (1) use of steel alloyed with strong carbide-forming elements, (2) use of liners of resistant alloy steels, and (3) substitution of resistant nonferrous alloys.
Author: Publisher: ISBN: Category : Languages : en Pages : 12
Book Description
J-integral fracture mechanics techniques and electron microscopy observations were used to investigate the effects of tritium and its radioactive decay product, 3He, on Types 316L, 304L and 21Cr-6Ni-9Mn stainless steels. Tritium-exposed-and-aged steels had lower fracture-toughness values and shallower sloped crack-growth-resistance curves than unexposed steels. Both fracture-toughness parameters decreased with increasing concentrations of 3He. The fracture-toughness reductions were accompanied by a change in fracture mode from microvoid-nucleation-and-growth processes in control samples to grain-and-twin-boundary fracture in tritium-charged-and-aged samples. Type 316L stainless steel had the highest fracture-toughness values and Type 21Cr-6Ni-9Mn had the lowest. Samples containing 3He but degassed of tritium had fracture toughness properties that were similar to uncharged samples. The results indicate that helium bubbles enhance the embrittlement effects of hydrogen by affecting the deformation properties and by increasing localized hydrogen concentrations through trapping effects.
Author: Jake Benzing Publisher: ISBN: Category : Liquid helium Languages : en Pages : 0
Book Description
In the framework of a collaborative project between ASME, NASA, and NIST, quasi-static fracture toughness tests have been performed at liquid nitrogen temperature (77 K, or -196 C) and liquid helium temperature (4 K, or -269 C) on weld specimens extracted from the centers of four 316L welded stainless steel plates, each produced by a different vendor. Although the plates were produced in accordance with the same specifications from the same material (316L), large differences in fracture toughness have been observed, with the best weld (W2) exhibiting twice the critical toughness of the worst (W1) at 77 K, and more than seven times the critical toughness of W1 at 4 K. The Charpy absorbed energies recorded at 77 K for three of the welds within the same project were found to be strongly linearly correlated with fracture toughness at both test temperatures. The exception was weld W4, which provided the highest impact toughness and the second lowest quasi-static fracture toughness (stable crack initiation and resistance to crack propagation).
Author: A. R. Elsea Publisher: ISBN: Category : Steel Languages : en Pages : 42
Book Description
This memorandum introduces the problem of delayed, brittle failures associated with hydrogen in steel, particularly high-strength steel. It is intended to help the steel user determine if he has such a problem. The effects of hydrogen on the mechanical properties of steel are dealt with, and the behavior of material susceptible to delayed, brittle failure is described. Also, the effects of such factors as strength level, magnitude of applied stress, hydrogen content, steel composition, test temperature, and strain rate on hydrogen embrittlement and the susceptibility to hydrogen-induced, delayed, brittle failure are discussed. Possible sources of hydrogen in steel and the types of tests useful in determining the susceptibility to delayed failure are outlined. (Author).
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Author: Ellis E. Fletcher
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Author: Alexander Robert Troiano
Author: Jake Benzing
Author: A. R. Elsea