Effects of Strain Rate and Microstructure on Fracture Toughness of Duplex Stainless Steels Under Hydrogen Charging Conditions

2011 ◽  
Author(s):  
Amir Bahrami ◽  
Anais Bourgeon ◽  
Mohamad Cheaitani
Keyword(s):  
Fracture Toughness ◽  
Stainless Steel ◽  
Strain Rate ◽  
Coarse Grained ◽  
Hydrogen Charging ◽  
Fine Grained ◽  
Stress Cracking ◽  
Flaw Tolerance ◽  
System Integrity ◽  
Ongoing Work

Failures of ferritic-austenitic stainless steel due to hydrogen induced stress cracking (HISC) have been very costly and raised concerns regarding subsea system integrity, some of which remain unresolved. The susceptibility to HISC crack initiation shows a strong correlation with austenite spacing and tests performed on smooth samples have shown that coarse-grained microstructures, with large austenite spacing, such as in forgings, are more susceptible to HISC than fine grained structures, eg as in pipe [1]. In all reported failures, cracking has been independent of the presence of fabrication flaws, even though welds were typically present, and initiated at external stress concentrators, so the importance of flaws remains undetermined. There is no well established method for determining fracture toughness values applicable to flaws in duplex stainless steel in the presence of hydrogen and hence reliable data do not exist, leading to a lack of understanding of the criticality of flaws and whether fine austenite spacing provides any benefit in resistance to extension of flaws. This paper provides new data from fracture toughness tests conducted on duplex pipe and forging parent materials, to explore the effect of product type/ microstructure and strain rate on fracture toughness under active charging in seawater under cathodic polarisation. This is part of ongoing work aimed at the development of an engineering critical assessment (ECA) approach for assessing flaw tolerance under hydrogen charging conditions.

Correlation between dislocation, grain boundary and interface of duplex SS in stress corrosion cracking(SCC)

1990 ◽  
Vol 48 (4) ◽  
pp. 928-929
Author(s):  
Wang Zheng-fang ◽  
Z.F. Wang
Keyword(s):  
Stainless Steel ◽  
Thermal Cycle ◽  
Secondary Phase ◽  
Corrosion Cracking ◽  
Coarse Grained ◽  
Test Environment ◽  
Fine Grained ◽  
Evaluation Test ◽  
Welding Thermal Cycle ◽  
Micro Analysis

The main purpose of this study highlights on the evaluation of chloride SCC resistance of the material,duplex stainless steel,OOCr18Ni5Mo3Si2 (18-5Mo) and its welded coarse grained zone(CGZ).18-5Mo is a dual phases (A+F) stainless steel with yield strength:512N/mm2 .The proportion of secondary Phase(A phase) accounts for 30-35% of the total with fine grained and homogeneously distributed A and F phases(Fig.1).After being welded by a specific welding thermal cycle to the material,i.e. Tmax=1350°C and t8/5=20s,microstructure may change from fine grained morphology to coarse grained morphology and from homogeneously distributed of A phase to a concentration of A phase(Fig.2).Meanwhile,the proportion of A phase reduced from 35% to 5-10°o.For this reason it is known as welded coarse grained zone(CGZ).In association with difference of microstructure between base metal and welded CGZ,so chloride SCC resistance also differ from each other.Test procedures:Constant load tensile test(CLTT) were performed for recording Esce-t curve by which corrosion cracking growth can be described, tf,fractured time,can also be recorded by the test which is taken as a electrochemical behavior and mechanical property for SCC resistance evaluation. Test environment:143°C boiling 42%MgCl2 solution is used.Besides, micro analysis were conducted with light microscopy(LM),SEM,TEM,and Auger energy spectrum(AES) so as to reveal the correlation between the data generated by the CLTT results and micro analysis.

Tensile Ductility of Ultra-Fine Grained Copper at High Strain Rate

2010 ◽  
Vol 160-162 ◽  
pp. 260-266 ◽  
Author(s):  
Tao Suo ◽  
Kui Xie ◽  
Yu Long Li ◽  
Feng Zhao ◽  
Qiong Deng
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Testing Machine ◽  
Coarse Grained ◽  
Dislocation Dynamic ◽  
Pressing Method ◽  
Fine Grained ◽  
Angular Pressing ◽  
Split Hopkinson

In this paper, ultra-fine grained copper fabricated by equal channel angular pressing method and annealed coarse grained copper were tensioned under both quasi-static and dynamic loading conditions using an electronic universal testing machine and the split Hopkinson tension bar respectively. The rapture surface of specimen was also observed via a Scanning Electron Microscope (SEM). The experimental results show that the ductility of polycrystalline copper decreases remarkably due to the grain refinement. However, with the increase of applied strain rate, ductility of the UFG-Cu is enhanced. The fracture morphologies also give the evidence of enhanced ductility of UFG-Cu at high strain rate. It is believed the enhanced ductility of UFG materials at high strain rate can be attributed to the restrained dislocation dynamic recovery.

High strain rate superplasticity in the fine-grained duplex stainless steel Fe-22Cr-5Ni-3Mo-0.3N

1996 ◽  
Vol 67 (10) ◽  
pp. 444-449 ◽  
Author(s):  
David Hernandez ◽  
Georg Frommeyer ◽  
Harald Hofmann
Keyword(s):  
Stainless Steel ◽  
High Strain Rate ◽  
Strain Rate ◽  
Duplex Stainless Steel ◽  
High Strain ◽  
Fine Grained

Cavitation Behavior of Ultra-Fine Grained Ti-6Al-4V Alloy Produced by Equal-Channel Angular Pressing

2007 ◽  
Vol 551-552 ◽  
pp. 621-626
Author(s):  
Young Gun Ko ◽  
Yong Nam Kwon ◽  
Jung Hwan Lee ◽  
Dong Hyuk Shin ◽  
Chong Soo Lee
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Equal Channel Angular Pressing ◽  
Cavity Growth ◽  
Rate Sensitivity ◽  
Theoretical Models ◽  
Coarse Grained ◽  
Fine Grained ◽  
Angular Pressing ◽  
Cavitation Behavior

Cavitation behavior during superplastic flow of ultra-fine grained (UFG) Ti-6Al-4V alloy was established with the variation of grain size and misorientation. After imposing an effective strainup to 8 via equal-channel angular pressing (ECAP) at 873 K, alpha-phase grains were markedly refined from 11 μm to ≈ 0.3 μm, and misorientation angle was increased. Uniaxial-tension tests were conducted for initial coarse grained (CG) and two UFG alloys (ε = 4 and 8) at temperature of 973 K and strain rate of 10-4 s-1. Quantitative measurements of cavitation evidenced that both the average size and the area fraction of cavities significantly decreased with decreasing grain size and/or increasing misorientation. It was also found that, when compared to CG alloy, cavitation as well as diffused necking was less prevalent in UFG alloys, which was presumably due to the higher value of strain-rate sensitivity. Based on the several theoretical models describing the cavity growth behavior, the cavity growth mechanism in UFG alloys was suggested.

Properties of Cryogenic Treated Cemented Carbides (WC-Co)

2020 ◽  
Vol 403 ◽  
pp. 75-89
Author(s):  
Vojtěch Průcha ◽  
David Bricín ◽  
Antonín Kříž ◽  
Zdeněk Jansa
Keyword(s):  
Fracture Toughness ◽  
Cryogenic Treatment ◽  
The Other ◽  
Coarse Grained ◽  
Cemented Carbides ◽  
Polished Surface ◽  
X Ray Diffraction ◽  
Deep Cryogenic Treatment ◽  
Fine Grained ◽  
Disk Test

The present paper explores the effects of deep cryogenic treatment (DCT) on the properties of WC-Co cemented carbides. The investigation involved four different cemented carbide (CC) grades. Two of them were coarse-grained WC with grain sizes larger than 6 μm and binder fractions of 10 and 15 wt. %. The other two were fine-grained with WC grains of 0.5-0.8 μm and the same binder fractions of 10 and 15 wt. %. Their specimens were ground and polished to prepare them for DCT. In each specimen, one half of this polished surface was used for testing the properties of the CC before cryogenic treatment. The post-DCT properties were then determined on the other half. Properties of the cemented carbides prior to and after DCT were studied using optical and scanning electron microscopy, X-ray diffraction, hardness testing according to Vickers scale followed by calculation of fracture toughness KIC and a ball-on-disk test of the wear resistance of the surface. One of the findings was that cryogenic treatment led to a decrease in residual stresses and to lower fracture toughness KIC in the CC.

Deformation and Fracture Behavior of AISI 403 Stainless Steel for Nuclear Structural Applications

2013 ◽  
Vol 794 ◽  
pp. 460-467
Author(s):  
C. Gupta ◽  
J.K. Chakravartty ◽  
R.N. Singh
Keyword(s):  
Fracture Toughness ◽  
Stainless Steel ◽  
Deformation Behaviour ◽  
Stable Crack Growth ◽  
Dynamic Strain ◽  
Tensile Behaviour ◽  
Temperature Range ◽  
Fine Grained ◽  
Deformation And Fracture ◽  
Structural Applications

The deformation and fracture behaviour of AISI 403, a tempered martensitic stainless steel for end fitting application of Pressurised heavy water reactor is being reported. The deformation behaviour studies entailed characterisation of tensile behaviour in the temperature range 77 - 873 K for the as recieved and the fine grained Nb modified variant of AISI 403. the study of elevated tensile behaviour in the two steels has been undertaken with the purpose of characterising the strain rate - temperature domain of the occurrence of dynamic strain aging (DSA) phenomenon. In both steels, while the temperature range for the manifestations of characteristic anomalies in the tensile curve due to DSA was observed within 523 - 673K, the strain domain for the fine grained Nb modfied variety was significantly higher as comapred with the as recievied variety. The low temperature tensile tests for the as recieved AISI 403 revealed the presence of Pseudo=alloy softening in the temperature range 273 - 193 K. The effect of high DBTT of the AISI 403 steel was shown by the fracture toughness tests in the J-integral format at room temperature that displayed significant scatter in smaples with high in-plane and out of plane constraint. Smaples with lower constraint showing stable crack growth were further tested at high temperature to obtain the temperature dependence of initiation fracture toughness and propagation touhgness. Within the DSA tempertaures a sharp decline in the fracture properties were observed. A mechanistic interpretation for the manifestations of the various observed phenomena is presented.

scholarly journals Effect of Strain Rate on the Fracture Toughness of Borated Stainless Steel

2019 ◽  
Vol 68 (8) ◽  
pp. 622-627
Author(s):  
Naohiro ITO ◽  
Shota HASUNUMA ◽  
Takeshi OGAWA ◽  
Satoru YONEYAMA
Keyword(s):  
Fracture Toughness ◽  
Stainless Steel ◽  
Strain Rate ◽  
Borated Stainless Steel

scholarly journals An analysis of compressive strain in adjacent temperature-gradient and equi-temperature layers in a natural snow cover

1980 ◽  
Vol 26 (94) ◽  
pp. 283-289 ◽  
Author(s):  
Richard L. Armstrong
Keyword(s):  
Strain Rate ◽  
Snow Cover ◽  
Compressive Strain ◽  
Coarse Grained ◽  
Adjacent Layer ◽  
Dominant Type ◽  
Fine Grained ◽  
Order Of Magnitude ◽  
Alpine Research ◽  
Natural Snow

AbstractCompressive strain-rates in discrete layers of a sub-alpine snow cover are analyzed. Individual layers are identified according to density and the dominant type of metamorphism which contributed to their formation. Data were collected during four winter seasons at the Institute of Arctic and Alpine Research (INSTAAR) snow-study site (3 400 m), Red Mountain Pass, south-western Colorado, U.S.A. At average densities of less than 250 kg m₋3the influence of metamorphism on strain-rate is not apparent. However, at densities greater than 250 kg m₋3, two separate relationships emerge for strain as a function of crystal type and density. While two adjacent layers may exhibit comparable densities, a layer of sintered, fine grained (ET) snow indicates a strain-rate approximately one order of magnitude greater than an adjacent layer of cohesionless, coarse-grained (TG) snow.

Effect of alloy grain size on oxidation resistance of silica-coated stainless steel

1994 ◽  
Vol 52 ◽  
pp. 676-677
Author(s):  
C. S. McDowell ◽  
S. N. Basu
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Stainless Steel ◽  
Oxidation Resistance ◽  
Powder Processing ◽  
Hot Isostatic Pressing ◽  
Silica Coating ◽  
Austenitic Steels ◽  
Coarse Grained ◽  
Fine Grained

Oxidation resistance of stainless steels, which rely on the formation of a Cr2O3 (chromia) scale, can be further improved through minor alloying additions such as Al or Si, or by application of coatings to the exposed surfaces. Although, additions of Si to austenitic steels have demonstrated an improvement in oxidation resistance, high Si contents can be detrimental to the mechanical properties of these alloys. The application of a silica coating on the surface of the stainless steel provides improved oxidation resistance without detrimental effects on the mechanical properties. This study examines the effect of the grain size of the stainless steel on the effectiveness of a silica coating as an oxidation barrier.Fully austenitic stainless steel of composition Fe-18(wt%)Cr-20Ni-1.5Mn was produced in both coarsegrained and fine-grained form. The coarse-grained alloy, with a grain size of approximately 100 μm, was produced by casting and hot rolling. The fine-grained alloy, with a grain size of approximately 5 μm, was produced by rapid solidification powder processing, followed by consolidated by hot isostatic pressing and swaging.

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