Showing papers on "Stress corrosion cracking published in 1985"
TL;DR: Friction and wear of Si3N4 sliding on itself were measured at room temperature in different gaseous and liquid environments as discussed by the authors, showing that wear occurs by two fracture mechanisms: within 1 μm of the surface, asperity contact produces very large local stresses and cracking on a very fine scale; 3-5 μm deeper the fracture follows weaknesses of the material and is intergranular fracture with some transgranular cleavage.
403 citations
TL;DR: In this paper, the authors reviewed the experimental and theoretical background of this form of metal failure and demonstrated the discontinuous nature of crack growth in α-brass and copper using a combination of acoustic and electrochemical measurements.
Abstract: The transgranular stress-corrosion cracking of ductile alloys (and at least one pure metal) leads to a fracture appearance characteristic of cleavage. The experimental and theoretical background of this form of metal failure is reviewed. The discontinuous nature of crack growth in α-brass and copper is demonstrated using a combination of acoustic and electrochemical measurements. Short-range cleavage of ductile metals is shown to be theoretically possible provided the thin surface film which is responsible for crack initiation has the appropriate properties. The important parameters determining the effectiveness of films in initiating cleavage include the film-substrate misfit, the strength of the bonding across the film-substrate interface, the film thickness and the film ductility. Suitable combinations of these parameters which can lead to micro cleavage are determined by the state of coherency of the interface and the fracture toughness of the substrate. For example, if a ductile de-alloyed l...
249 citations
TL;DR: In this article, the authors describe current understanding of the propagation of transgranular stress corrosion cracking (TGSCC) in engineering alloys, focusing on a new approach, the film-induced cleavage model.
Abstract: This paper describes current understanding of the propagation of transgranular stress corrosion cracking (TGSCC) in engineering alloys. In contrast to intergranular stress corrosion cracking (IGSCC), which proceeds by preferential anodic dissolution at the crack tip, TGSCC is considered to propagate by discontinuous brittle fracture (cleavage). First, the propagation process is described, outlining current knowledge of the crystallography of the cleavage surfaces and reviewing the evidence for the discontinuous nature of cracking. An evaluation follows of the models that are currently proposed to explain how interaction with the chemical environment induces brittle fracture in normally ductile alloys, focusing, in particular, on a new approach, the film-induced cleavage model. Finally, attention is directed to step formation between the parallel, but displaced, primary cleavage facets. It is suggested that step formation, which in face-centered cubic (fcc)alloys occurs by highly localized plastic...
88 citations
TL;DR: In this article, a nuclear reactor pressure vessel steel in pure water at temperatures from 150 to 288°C and at various oxygen contents was tested and it was confirmed that the oxygen in the water acts as a chemical potentiostat, which drives the steel into or out of the cracking range, by showing that cracking could be prevented in 45 ppm O2 water at 288°c by applying cathodic polarization.
88 citations
TL;DR: In this article, a stress corrosion cracking (SCC) mechanism is proposed in which anodic dissolution at film rupture sites relieves strain hardening and reduces the fracture stress at the crack tip.
Abstract: A mechanism of stress corrosion cracking (SCC) is outlined in which anodic dissolution at film rupture sites relieves strain hardening and reduces the fracture stress at the crack tip. Experimental evidence is cited to suggest that relief of strain hardening occurs by interaction of subsurface dislocations with divacancies generated by the anodic dissolution. A transgranular crack propagates by accumulation of divacancies on prismatic planes which then separate by cleavage under plane strain conditions at the crack tip. At appropriate metallurgical and chemical conditions, anodic dissolution and/or divacancy migration may be enhanced at grain boundaries, leading to an intergranular failure mode. Evidence is also available to indicate that cyclic loading relieves strain hardening. Relief of strain hardening by combined cyclic loading and corrosion accounts for the higher incidence of corrosion fatigue cracking (CFC) without the requirement of any critical dissolved species. Data on fatigue of stainless steel at elevated temperature in both vacuum and air provide additional support for the proposed mechanism.
76 citations
TL;DR: In this article, the authors investigated correlations between the extraction process, crack formation phenomena and fiber strength, and found that the degree of damage will generally depend upon several factors such as glass content, test temperature, and the aggressiveness of the chemical environment.
67 citations
TL;DR: In this paper, the influence of composition, heat-treatments, and microstructure of quenched and tempered Cr-Mo steels on their behavior under sulfide stress corrosion cracking is studied.
Abstract: The influence of composition, heat-treatments, and microstructure of quenched and tempered Cr-Mo steels on their behavior under sulfide stress corrosion cracking is studied. Starting from a lCr-0.2Mo steel, with a UTS of 1015 MPa, laboratory heats of lCr-0.8Mo, lCr-0.2Mo-V, lCr-0.2Mo-V-Ti, and lCr-0.8Mo-V-Ti steels are prepared and tempered to UTS of 900 to 1000 MPa. SSC tests are conducted in NACE solutions and show the beneficial influence of isolated or combined Mo, V, and Ti additions. The microstructural characterizations and a fundamental study of hydrogen permeation and hydrogen trapping in the microstructure (through high resolution autoradiography and vacuum desorption measurements) give the explanation of the SSC behavior of the steels. The good performances of the lCr-0.8Mo-V-Ti steel are attributed to the precipitation of very finely dispersed particles with an MC carbide type structure, which act both by retarding the tempering process and playing a role of good traps for hydrogen.
42 citations
TL;DR: Crack growth resistance curves have been determined for the stress corrosion cracking of two magnesium alloys in which the J-integral is plotted against crack extension as discussed by the authors, and the results are discussed in terms of the displacement and displacement rate occurring at the tip of the moving crack.
Abstract: Crack growth resistance curves have been determined for the stress corrosion cracking of two magnesium alloys in which theJ-integral is plotted against crack extension. As determined in this way, the resistance to crack growth initially falls with decreasing applied displacement rate but rises again at the slower rates. The effect is in line with previous results obtained on plain specimens and is thought to be due to increasing passivation at the slower testing rates. The results are discussed in terms of the displacement and displacement rate occurring at the tip of the moving crack.
34 citations
TL;DR: In this article, the similarities and differences in the stress corrosion cracking response of ferritic and austenitic stainless steels in chloride solutions were examined, and it was shown that the ferritic steels are more resistant to localized corrosion than are the austenititic steels.
Abstract: The similarities and differences in the stress corrosion cracking response of ferritic and austenitic stainless steels in chloride solutions will be examined. Both classes of materials exhibit a cracking potential: similar transient response (to loading) of the potential in open circuit tests or the current in potentiostatic tests and similar enrichment of chromium and depletion of iron in the film associated with localized corrosion processes. The ferritic steels are more resistant to localized corrosion than are the austenitic steels, which is responsible for the difference in the influence of prior thermal and mechanical history on cracking susceptibility of the two types of steel. Similarities in the fractography of stress corrosion cracks and those produced by brittle delayed failure during cathodic charging of the ferritic steels indicate that hydrogen embrittlement is involved in the failure process.
34 citations
32 citations
TL;DR: In this article, the effects of variations in grain-boundary microstructure on fracture in high-purity Al-6Zn-3Mg bicrystals in inert, liquid metal, and water environments are described.
Abstract: Metallographic and fractographic studies of intercrystalline fracture in high-purity Al-6Zn-3Mg bicrystals in inert, liquid metal, and water environments are described. The effects of variations in grain-boundary microstructure on fracture and the effects of cathodically charging specimens with hydrogen prior to testing in inert environments were also investigated. Mechanisms of liquid-metal embrittlement, stress-corrosion cracking and pre-exposure embrittlement are discussed in the light of these results. The observations suggest that liquid-metal embrittlement and stress-corrosion cracking generally occur by a plastic-flow/microvoid-coalescence process that is more localized than that which occurs in inert environments. It is proposed that adsorbed liquid metal or hydrogen atoms weaken interatomic bonds at crack tips, thereby facilitating the nucleation of dislocations and promoting the coalescence of cracks with voids.
TL;DR: Slow strain rate stress corrosion tests have been performed on Type 316 stainless steel in 265°C water containing from 0 to 45 ppm oxygen and from 1.5 to 5 ppm carbon dioxide.
TL;DR: In this article, the authors studied the stress corrosion cracking behavior of differently heat-treated specimens of Inconel 600 in 25 molal (m) NaOH solution at 140 C by using the slow strain rate technique (SSRT).
Abstract: The stress corrosion cracking (SCC) behavior of differently heat-treated specimens of Inconel 600 in 25 molal (m) NaOH solution at 140 C was studied as a function of potential by using the slow strain rate technique (SSRT). It was found that the cracking susceptibility and the failure mode (intergranular vs transgranular) depends heavily on potential, heat treatment, and grain size. In the mill-annealed condition, intergranular stress corrosion cracking (IGSCC) was obtained at potentials extending from the active peak (−900 mVSCE) to the secondary anodic peak (−400 mVSCE), while transgranular stress corrosion cracking (TGSCC) occurred at the open circuit potential (OCP), ∼−980 mVSCE, and at 0 mVSCE (secondary passive region). Solution-annealed material showed reduced IGSCC susceptibility with respect to the mill-annealed material, while almost complete IGSCC resistance was obtained by heat treatment at 700 C of both mill- and solution-annealed materials. Also, material with small grain size exhib...
TL;DR: In this article, a series of anionic inhibitors have been used to aid the passivation process of stainless steels due to stress corrosion cracking due to thiosulfate and tetrathionate.
Abstract: The stress corrosion cracking of sensitized stainless steels due to thiosulfate and tetrathionate has been associated with an increased rate of anodic dissolution in the active-passive region of voltammetric scans, via the mutual sensitivity of both phenomena to a series of anionic inhibitors. The increased anodic dissolution is caused by the adsorption of the sulfur compound and its catalysis of metal oxidation. The inhibitors function, not by competitivel desorbing the corrodent, but by aiding the passivation process.
TL;DR: In this article, a hydrogen embrittlement model of SCC was developed that predicts SCC performance on the basis of grain boundary chemistry and grain boundary carbides, and the presence of M23C6 type carbides and /or the absence of MC-type carbides at the grain boundaries.
Abstract: The high-strength, nickel-base alloy X-750 is susceptible to stress-corrosion cracking (SCC) in high-purity, deaerated water. Crack initiation occurs at high temperatures [>400°F (204 °C)]. Crack propagation occurs in both high-temperature and low-temperature [<300 °F (149 °C)] water. High-temperature crack growth rates are on the order of mils per day. Low-temperature cracking is extremely rapid [≈100 in. (250 cm) per day]. Three heat treatments of Alloy X-750 are investigated: (1) stress equalized—1625 °F (885 °C)/24 hours + 1300 °F (704 °C)/20 hours, (2) direct aged—1300 °F (704 °C)/24 hours, and (3) solution annealed and direct aged—2000 °F (1093 °C)/ 1 hour + 1300 °F (704 °C)/20 hours. Stress-equalized Alloy X-750 is most susceptible to SCC; solution-annealed and direct-aged Alloy X-750 is least susceptible. A hydrogen embrittlement model of SCC is developed that predicts SCC performance on the basis of grain boundary chemistry and grain boundary carbides. Phosphorus segregates to the grain boundary in concentrations of up to ≈700 times the bulk concentration during processing and heat treatment. Phosphorus at the grain boundaries increases susceptibility to high- and low-temperature SCC. The presence of M23C6-type carbides and /or the absence of MC-type carbides at the grain boundaries improves SCC performance in high-temperature water.
TL;DR: In this paper, the authors showed that hydrogen embrittlement is the rate determining step for stress corrosion cracking (SCC) of welded 7020 and postweld artificially aged.
Patent•
04 Jun 1985TL;DR: A sintered stainless steel exhibiting improved resistance to stress corrosion cracking which comprises a matrix phase and a dispersed phase is described in this article, where a process for manufacturing the same is described.
Abstract: A sintered stainless steel exhibiting improved resistance to stress corrosion cracking which comprises a matrix phase and a dispersed phase and a process for manufacturing same are disclosed. The dispersed phase is of an austenitic metallurgical structure and is dispersed throughout the matrix phase which is comprised of an austenitic metallurgical structure having a steel composition different from that of the dispersed phase or a ferrite-austenite duplex stainless steel.
TL;DR: In this paper, a commercial 0.19 pct C steel (SA-516 Grade 70) was studied in hot (92 ‡C) caustic solutions of NaOH and NaOH plus aluminate (AlO−¯¯¯¯ 2) species.
Abstract: Stress corrosion cracking of a commercial 0.19 pct C steel (SA-516 Grade 70) was studied in hot (92 ‡C) caustic solutions of NaOH and NaOH plus aluminate (AlO−
2) species. Potentiostatically controlled tests were conducted near the active-passive transition, using fracture mechanics testing techniques and fatigue precracked double cantilever beam specimens. Crack propagation rates (Ν) were determined for a range of stress intensities (K
l). In simple NaOH solutions, Region I (K1-dependent) and Region II (K
1-independent) cracking behavior were observed. Increasing the concentration of NaOH from2m to8m decreasedK
ISCC
and displaced Region I and the onset of Region II to lowerK
1 levels. The presence of AlO−
2 produced a comparable effect, with Region II being extended to lowerK
I
-Ν levels relative to simple NaOH solutions of similar hydroxyl anion concentration. The overallK
I
-Νv behavior and fractography were consistent with a dissolution mechanism of crack advance based on the general principles of the film rupture-dissolution model. The effect of environment composition uponK
I
— Ν behavior was attributed to changes in repassivation kinetics.
TL;DR: In this paper, the authors studied the SCC susceptibility of AISI 304 austenitic stainless steel in mixed HCl + NaCl solutions at room temperature and found that cracks were transgranular, and the experimental results showed that an anodic rate controlling step is present in this SCC process.
TL;DR: In this article, an experimental program was undertaken to assess the extent to which PWR pressure vessel steels, including weldments, may be susceptible to stress corrosion cracking under relevant water chemistry and flow rate conditions.
TL;DR: In this paper, a study of the effects of metallurgical and environment variables on stress corrosion cracking (SCC) propagation rates in NiCrMoV turbine disc steels was made.
Abstract: A study was made of the effects of metallurgical and environment variables on stress corrosion cracking (SCC) propagation rates in NiCrMoV turbine disc steels. Constant displacement tests, using wedge-opening-load (WOL) specimens, were performed on steels with yield strengths in the range of 627 to 1124 MPa. One steel was temper-embrittled to study the effect of phosphorus segregation on SCC growth rates. All tests were made at 157 C in either pure water environments, or environments containing common ionic turbine contaminants (NaCl and NaOH) and gaseous turbine contaminants (air, oxygen, and carbon dioxide). Crack growth occurred in all of these environments, although growth rates decreased with increasing environment purity. Estimated field crack growth rates were in close agreement with rates obtained in deaerated pure water. Crack growth was always intergranular, except in aerated pure water, when it was transgranular. Crack growth rates were found to increase with increasing yield strength....
TL;DR: In this article, it has been demonstrated with examples that, for the occurrence of stress corrosion cracking (SCC), time-dependent parameters as well as critical stress levels are highly important.
Abstract: It has been demonstrated with examples that, for the occurrence of stress corrosion cracking (SCC), time-dependent parameters as well as critical stress levels are highly important. Therefore, certain ideas that have developed concerning the differentiation between SCC and corrosion fatigue must be revised. When cyclic loading is involved, SCC, corrosion fatigue, and fatigue are successively encountered as the frequency or strain rate is increased, and such forms of material damage are therefore predominant in particular frequency ranges.
TL;DR: Etude des facteurs susceptibles de declencher cette corrosion, sous des conditions de contrainte elevees, dans les aciers faiblement allies au Mn-Ni-Mo.
Abstract: Etude des facteurs susceptibles de declencher cette corrosion, sous des conditions de contrainte elevees, dans les aciers faiblement allies au Mn-Ni-Mo
Patent•
13 Nov 1985
TL;DR: In this paper, the authors proposed a method to provide excellent resistance to hydrogen induced cracking and sulfide stress corrosion cracking to a steel sheet by heating a billet which is considerably decreased in the contents of P, S, O and N and is subjected to a morphology control treatment of MnS by addition of Ca, than rolling and cooling the same under specific conditions.
Abstract: PURPOSE: To provide excellent resistance to hydrogen induced cracking and sulfide stress corrosion cracking to a steel sheet by heating a billet which is considerably decreased in the contents of P, S, O and N and is subjected to a morphology control treatment of MnS by addition of Ca, than rolling and cooling the same under specific conditions. CONSTITUTION: The compsn. consisting, by wt%, of <0.15 C, <0.6 Si, 0.6W1.5 Mn, <0.007 P, <0.001 S, 0.005W0.1 Al, 0.003W0.03 Ti, 0.0005W0.004 Ca, <0.0025 O, and 0.0035 N, contg. the components satisfying formulas I, II, III and consisting of the balance Fe and inevitable impurities is used for the billet. Such billet is heated to 950W1,250°C and is then rolled at ≥60% rolling reduction at ≤900°C and the Ar 3 transformation point finishing temp. or above. The rolled sheet is cooled from the Ar 3 transformation point or above down to 350W550°C at 10W40°C/sec cooling rate upon ending of the rolling and is then allowed to cool. COPYRIGHT: (C)1987,JPO&Japio
TL;DR: In this article, the effects of microstructural changes on the caustic stress corrosion cracking resistance of a NiCrMoV rotor steel were studied and the results showed that heat treatments which produced large, chromiumrich carbides are beneficial.
Abstract: This paper presents a study of the effects of microstructural changes on the caustic stress corrosion cracking resistance of a NiCrMoV rotor steel. All tests were run in 9 M NaOH at 98 °C and at an electrochemical potential of −400 mVHg/Hgo. Different microstructures were obtained by tempering martensitic samples for different times at 600 °C or by using a slow controlled cool from the austenite to produce a bainitic structure. The results show that heat treatments which produced large, chromiumrich carbides are beneficial. These carbides are preferentially corroded and cause pits to form at the crack tip. We propose that these pits cause crack tip blunting and slow crack propagation. It is further shown that, although changes in microstructure can produce improvements in the susceptibility to stress corrosion cracking, these changes cannot compensate for the detrimental effects of phosphorus segregation to grain boundaries.
TL;DR: In this article, the authors reported a study of stress corrosion cracking of Fe-3Ni and Fe-0.06P alloys in 9M NaOH and showed that the presence of carbon or carbides degrades the caustic cracking resistance of low alloy steels but that small additions of vanadium and chromium have little effect.
Abstract: This paper reports a study of stress corrosion cracking of Fe-3Ni, Fe-3Ni-0.5Mo, and Fe-3Ni-0.06P alloys in 9M NaOH. The samples were tested at 98 C and at −400 mVHg/HgO under constant load. The results show that Fe-3Ni is very resistant to caustic stress corrosion and that additions of 0.5Mo degrade this resistance only slightly. However, phosphorus segregation to grain boundaries significantly impairs caustic cracking resistance. Possible mechanisms for the effect of phosphorus and molybdenum on caustic stress corrosion cracking are considered. It will also be demonstrated by comparison of these data with those obtained on low alloy steels that the presence of carbon or carbides degrades the caustic cracking resistance of iron base alloys but that small additions of vanadium and chromium have little effect. Segregated sulfur also has no effect on the cracking process.
Book•
01 Jan 1985
TL;DR: In this paper, the microstructure of Inconel X-750 alloy was studied after a number of different heat treatments and the corrosion resistance was evaluated based on intergranular corrosion and stress corrosion cracking test results.
TL;DR: Stress corrosion cracking (SCC) tests were conducted in 1N AlCl3 solution on 7075 aluminum in three tempers: T6, T73, and an underaged temper (UT) approximately equal in strength to T73.
Abstract: Stress corrosion cracking (SCC) tests were conducted in 1N AlCl3 solution on 7075 aluminum in three tempers: T6, T73, and an underaged temper (UT) approximately equal in strength to T73. T...