Showing papers on "Stress corrosion cracking published in 1978"

Surface normalization of sensitized stainless steel by laser surface melting

Abstract: A scanning laser beam was used to melt and normalize the surface layer of sensitized 304 stainless steel. Subsequent Strauss tests indicated a complete resistance to intergranular corrosion. Mechanical testing at strains less than 15% also showed laser surface melting to indefinitely extend specimen life in a stress corrosion environment. At strains greater than 15%, the laser‐scanned protective layer was breached by cracks. A maximum critical laser‐scanning velocity compatible with normalization of the surface layer is calculated. Similarly, a minimum critical laser‐scanning velocity required to avoid resensitization is determined. The stress distribution in a 304 stainless‐steel specimen with a laser‐melted and self‐quenched surface layer is estimated and shown to be compatible with the observed appearance of martensite in the melted surface layer.

Effects of silicon additions and retained austenite on stress corrosion cracking in ultrahigh strength steels

Abstract: A study has been made of the effects of silicon additions and of retained austenite on the stress-corrosion cracking (SCC) behavior of commercial ultrahigh strength steels (AISI 4340 and 300-M) tested in aqueous solutions. By comparing quenched and tempered structures of 4340 and 300-M i) at equivalent strength and ii) at their respective optimum and commercially-used heat-treated conditions, the beneficial role of silicon addition on SCC re-sistance is seen in decreased Region II growth rates, with no change in K’ISCC. The beneficial role of retained austenite is demonstrated by comparing isothermally transformed 300-M, containing 12 pct austenite, with conventionally quenched and tempered structures of 300-M and 4340, containing less than 2 pct austenite, at identical yield strength levels. Here, the isothermally transformed structure shows an order of magnitude lower Region II SCC growth rates than quenched and tempered 300-M and nearly two orders of magnitude lower Region II growth rates than 4340, K ISCC values remaining largely unchanged. The results are discussed in terms of hydrogen embrittlement mechanisms for SCC in martensitic high strength steels in the light of the individual roles of hydrogen diffusivity and carbide type.

Low Temperature Sensitization of Welded Type 304 Stainless Steel

Abstract: It has been shown that the sensitization of Type 304 stainless steel occurs at temperatures well below the normal isothermal temperature range for sensitization. A prerequisite for this low temperature sensitization (LTS) is the presence of chromium carbide nuclei along grain boundaries. This paper shows that the thermal exposure during welding can nucleate the grain boundary carbides necessary for subsequent LTS. Quantitative transmission electron microscopy studies show that no new carbides nucleate during an LTS heat treatment at 400 C. However, carbides that were nucleated at the time of welding grow during the LTS heat treatment. These findings are consistent with the proposed nucleation and growth LTS model. Using an accelerated test for intergranular stress corrosion cracking (IGSCC) in high temperature, high purity, 8 ppm oxygen water, it has been found that the rate of LTS in a Type 304 stainless steel weld heat affected zone obeys an Arrhenius temperature dependence which predicts that ...

Basal and near- basal hydrides in Ti- 5AI- 2.5Sn

Abstract: Cleavage cracking of titanium alloys has been reported to occur under conditions of stress corrosion cracking and sustained load cracking and, in such cases, the cleavage plane has often been reported as being near-basal, typically 14 to 16 deg from (000I)α However, the indices of this cleavage plane have not yet been definitely established, nor has the reason for its occurrence. In the present work the Ti-5Al-2.5Sn alloy has been hydrogenated to various levels and three hydride phases are found to occur. The first to precipitate is the y-hydride, occurring at 00123300 ppm H2. At 00123500 ppm H2 a near-basal hydride of unknown crystal structure is formed. There is no unique habit plane. At concentrations in excess of 600 ppm, hydrogen-stabilized stacking faults occur on the basal plane. The significance of these hydride phases is discussed with reference to stress corrosion cracking and sustained load cracking.

The deformation and fracture kinetics of stress corrosion cracking

Abstract: The concepts of deformation and fracture kinetics theory are extended for the analysis of stress corrosion cracking. A single, coherent system is developed that provides the full kinetics description of the typical SCC behavior. The kinetics approach shows that Regions I and II are associated with two consecutive energy barriers, parallel with the single barrier associated with Regon III. The kinetics analysis of two consecutive barriers leads to a four-term expression, rather than to the generally considered two-term form. The effect of the threshold stress intensity is predicted by the complete desxription of the consecutive barrier system.

Corrosion behavior of cast and forged cobalt-based alloys for double-alloy joint endoprostheses†

Abstract: An ideal combination of mechanical and corrosion properties of long-term implants such as joint endoprostheses has yet to be found. Besides being resistant to pitting and crevice attack, which can lead to corrosion fatigue and stress corrosion cracking failures, the implant material must be highly resistant to wear and abrasion. Two cobalt-based alloys, wrought CoNiMoTi and air-cast CoCrMo, were subjected to a number of selected in vitro electrochemically and chemically accelerated corrosion tests in chloride-containing solutions with wrought AISI-316L used as a reference alloy. A limited number of immersion tests in FeCl3 and acidified FeCl3 solutions were also conducted. It is found that the mechanical properties of wrought CoNiCrMoTi alloy qualify it as a substitute for cast CoCrMo alloy and wrought AISI-316L in anchorage shaft production for all types of joint endoprostheses. Wrought CoNiCrMoTi has a higher resistance to fatigue cracking compared with cast CoCrMo and is as resistant to selective corrosion phenomena such as stress corrosion cracking.

Stress Corrosion Cracking of C-Mn Steel in Phosphate Solutions

Abstract: Annealed C-Mn steel has been shown to fail by transgranular stress corrosion cracking (SCC) in sodium phosphate solutions over a range of potentials and pH's at room temperature. The obser...

Method of making a structure immune against stress corrosion cracking

Abstract: A groove is provided on the side of a metallic structure opposite to the side thereof which is exposed to a corrosive atmosphere, and the groove is subjected to build-up welding while cooling with a liquid coolant, whereby any stress corrosion cracking which otherwise occurs on the side of the structure to be exposed to the corrosive atmosphere can be prevented. Especially, this method of manufacture is appropriate for the repair welding of a butt-welded pipe of austenite type stainless steel, and it is effective to perfectly prevent the stress corrosion cracking of the pipe prone to be caused by reactor water during use in a nuclear reactor.

Stress Corrosion Cracking of Low Strength, Low Alloy Nickel Steels in Sulfide Environments

Abstract: Factors governing stress corrosion cracking (SCC) of low strength, low alloy nickel steels (e.g., ASTM A203 Grade E) in sulfide environments were investigated using a three point loaded be...

Die Wirkung mechanischer Einflußgrößen bei der Rißkorrosion von Kohlenstoff‐Mangan‐Stählen. Mechanical Factors Influencing Corrosion Cracking of Carbon‐Manganese Steels

Abstract: Stand des Wissens uber Spannungsris- und Schwingungsriskorrosion bis um 1970; spezifische Medien fur Spannungsriskorrosion: Alkalilauge, Nitrate, Ammoniumsalze – Bedeutung der constant-strain-rate-Technik und Bikarbonat-Spannungsriskorrosion – Zeitabhangigkeit von Zugspannung, Dehnung und Dehngeschwindigkeit; Bedeutung der Dehngeschwindigkeit – Untersuchungen in Bikarbonat-, Karbonat- und Hydroxidlosungen – kritische Potentialbereiche – Zusammenhang zwischen Dehngeschwindigkeit und langsamer Ermudung – theoretischer Unterschied zwischen Spannungsriskorrosion und Korrosionsermudung trotz phanomenologisch gleitender Ubergange. Knowledge about stress corrosion cracking and corrosion fatigue until 1970; specific aggressive media to cause stress corrosion cracking: alkali solution, nitrates, ammonia salts – meaning of the constant strain rate technique and stress corrosion cracking in bicarbonate solutions – dependence of tensile stress, strain and strain rate upon time; significance of strain rate – investigations in bicarbonate, carbonate and hydroxide solutions – critical potential ranges – relation between strain rate and low cycle fatigue – theoretical differences between stress corrosion cracking and corrosion fatigue in spite of gradual transient in physical appearances.

Caustic Stress Corrosion Cracking Studies at 288 C (550 F) Using the Straining Electrode Technique — Comparison of Alloy 600, Alloy 800, and Type 304 Stainless Steel

Abstract: Constant pull rate tests were conducted on tensile specimens of Inconel Alloy 600, Incoloy Alloy 800, and Type 304 stainless steel in deaerated 10% NaOH solution at 288 C (550 F) with a co...

Prediction of stress corrosion of carbon steel by nuclear process liquid wastes

Abstract: Radioactive liquid wastes are produced as a consequence of processing fuel from Savannah River Plant (SRP) production reactors. These wastes are stored in mild steel waste tanks, some of which have developed cracks from stress corrosion. A laboratory test was developed to determine the relative agressiveness of the wastes for stress corrosion cracking of mild steel. Tensile samples were strained to fracture in synthetic waste solutions in an electrochemical cell with the sample as the anode. Crack initiation is expected if total elongation of the steel in the test is less than its uniform elongation in air. Cracking would be anticipated in a plant waste tank if solution conditions were equivalent to test conditions that cause a total elongation that is less than uniform elongation. The electrochemical tensile tests showed that the supernates in salt receiver tanks at SRP have the least aggressive compositions, and wastes newly generated during fuel repocessing have the most aggressive ones. Test data also verified that ASTM A 516-70 steel used in the fabrication of the later design waste tanks is less susceptible to cracking than the ASTM A 285-B steel used in earlier designs.

Method of manufacturing aluminum alloy sheets containing magnesium and zinc

Abstract: The present invention resides in the manufacture of an AlMg alloy sheet with zinc addition which is readily deformable in the soft condition and especially suited for shaping into motor vehicle body components. The alloy sheet has a strength of at least 250 N/mm 2 , a grain size of less than 50 μm and, after deformation has occurred, remains free of surface defects such as orange peel effect and Luders bands and also, after a possible influence of heat, remains insensitive to stress corrosion cracking. The zinc addition produces a widening of the working range so that after the last cold rolling operation the alloy can be soft annealed above the recrystallization temperature without coarse grains or Luders band appearing. The zinc addition produces an insensitivity with respect to stress corrosion cracking after a heterogenization annealing subsequent to the soft annealing, even after a sensitization at 150° C. on a sheet which has been deformed with a cold reduction of 20% and more.

Stress corrosion cracking of high strength HY-180M steel in 3.5 Pct NaCl

Abstract: Stress corrosion cracking of HY-180M steel was studied at 22°C in an aqueous solution of 3.5 pct NaCl (pH = 6.5). The steel had a nominal weight percentage composition of 10Ni-14Co-2Cr-lMo-0.16C and was heat treated to yield a fracture toughness value ofK Ic ≃ 160 MPa . m1/2. The SCC velocity (v) was studied as a function of stress intensity (K I) and electrochemical potential (E) using precracked compact tension specimens, a Ag/AgCl reference electrode and a 1000 h exposure test. Also, the polarization behavior, microstructure, fractography and corrosion products were studied. The results showed that SCC was markedly dependent uponE, and did not occur whenE =-0.52 VSHE (-0.72 VAg/AgCl), which corresponded closely to the thermodynamically reversible potential of iron. However, SCC occurred at a more noble potential of-0.28 VSHE (-0.48 VAg/AgCl ) and at a less noble potential of-0.80 VSHE (-1.00 VAg/AgCl). The stress intensity below which SCC was not observed was KISCC ≃ 5.5 MPa . m1/2 at -0.28 VSHE and KISCC ≃ 60 MPa . m1/2 at -0.80 VSHE . Also, Region I behavior (v dependent uponK 1) and Region II behavior (v independent ofK 1) were observed. Cracking was considered to occur solely by hydrogen embrittlement at -0.80 Vshe, whereas anodic dissolution processes played a necessary role, either directly or indirectly, in SCC at -0.28 VSHE . The indirect effects were discussed in relation to hydrolysis effects in the crack promoting hydrogen embrittlement and/or corrosion product wedging stresses.

Critical Cooling Rate of 18Cr-8Ni Stainless Steel for Sensitization and Subsequent Intergranular Stress Corrosion Cracking in High Temperature Water

Abstract: Calculation of critical cooling rates for sensitization occurring in transient metal forming processes of austenitic stainless steel were carried out using isothermal time-temperature-sensitization curves. A series of 18Cr-8Ni stainless steels each containing a different level of carbon were melted and cooled at various rates from a solution annealing temperature. Two types of tests were run on these alloys to evaluate the degree of sensitization. One test was the 10% oxalic acid electrolytic etch test. The other technique was constant strain rate tests which were conducted at a strain rate of 5 x 10−4 minute−1 in aerated high temperature water containing 10 ppm chloride ions. A good correlation was found between both sets of tests results. Dual structures exhibited intergranular cracking. An actual critical cooling rate for sensitization and subsequent intergranular stress corrosion cracking (SCC) was located in the range between two calculated critical cooling rates.

Stress Corrosion Cracking and Anodic Behavior of AISI 304 Stainless Steel, Inconel 600, and Incoloy 800 Straining in Boiling NaOH Solutions

Abstract: The straining electrode technique was used to evaluate the stress corrosion cracking (SCC) susceptibility of AISI 304 stainless steel in 20N NaOH solution, and of Inconel 600 Alloy and Incoloy 800 Alloy in boiling 17.5N NaOH solution. The crack propagation rate estimated from the straining experiments correlated well with failure time measurements from previous constant load experiments. It was found that the straining electrode technique is a useful method for estimating, through short term experiments, parameters like crack propagation rate, crack morphology, and repassivation rate, as a function of the electrode potential.

EPRI-NASA Cooperative Project on Stress Corrosion Cracking of Zircaloys

Abstract: Examinations of the inside surface of irradiated fuel cladding from two reactors show the Zircaloy cladding is exposed to a number of aggressive substances, among them iodine, cadmium, and iron-contaminated cesium. Iodine-induced stress corrosion cracking (SCC) of well characterized samples of Zircaloy sheet and tubing was studied. Results indicate that a threshold stress must be exceeded for iodine SCC to occur. The existence of a threshold stress indicates that crack formation probably is the key step in iodine SCC. Investigation of the crack formation process showed that the cracks responsible for SCC failure nucleated at locations in the metal surface that contained higher than average concentrations of alloying elements and impurities. A four-stage model of iodine SCC is proposed based on the experimental results and the relevance of the observations to pellet cladding interaction failures is discussed.

Stress Corrosion Cracking of Turbine Disc and Rotor Alloys

Abstract: Investigations have been carried out to examine the stress corrosion behaviour of some medium strength low alloy steels in high purity wet steam and water. The alloys involved are used for the manufacture of steam turbine discs and rotors.Stress corrosion cracking occurred in both 3% CrMo and 31/2% NiCrMoV steels. Crack growth rates were measured, after exposure in on-site rigs, for periods up to 20,000 h. The effects of applied stress, stress intensity, and strength level were studied in addition to microstructure. The possible role of certain non-metallic incluszons upon the cracking process is highlighted, as is the presence of chromium.

Alloys resistant to localized corrosion, hydrogen sulfide stress cracking and stress corrosion cracking

Abstract: An alloy and a metal product characterized by resistance to localized corrosion, hydrogen sulfide stress cracking (hydrogen embrittlement) and stress corrosion cracking at temperatures up to about 200° C. consisting essentially of nickel 40-65%, cobalt 0-5%, chromium 10-20%, molybdenum 12-18%, iron 10-20%, tungsten up to 5%, carbon 0-0.1% manganese up to 3%, vanadium up to 1% and silicon up to 0.2%. The alloy resistance is maintained when it is cold worked over 20%.

Stress Corrosion Cracking and Corrosion Fatigue of Some Surgical Implant Materials in a Physiological Saline Environment

Abstract: The results of slow strain rate tensile tests and concomitant fractography suggest that cast Vitallium and Type 316L stainless steel, which are widely used for surgical implants, are not susceptible to stress corrosion cracking (SCC) in a physiological saline (Tyrode's) solution. Several high strength, high ductility stainless steels (TRIP steels), which are candidates for implant use, also appeared to be immune to SCC. Some combinations of TRIP steel composition and metallurgical condition showed significantly lower elongations to failure in Tyrode's solution than in air, but no fractographic evidence of SCC was obtained. The susceptibilities to corrosion fatigue of cold worked Type 316L and two TRIP steels were assessed by comparing the fatigue lives of smooth specimens tested in argon and Tyrode's solution. All three materials generally showed lower fatigue lives in the saline environment, the degree of life reduction being dependent on electrochemical potential. Although additional research i...

A -zn-mg alloy for hollow extruded shapes with superior characteristics at its deposited part

Abstract: PURPOSE: To provide an Al alloy for hollow extruded shapes with superior extrusibility, bending ductility at its deposited part and stress corrosion cracking resistance by adding B, Be, Mn, Cr, Zr, Ti, etc. CONSTITUTION: An Al-Zn-Mg alloy contg. Zn; 3W9%, Mg; 0.3W2% and Cu; 0.1W0.8% as essential components. The alloy may further contain B; 0.001W0.10% and/or Be; 0.001W0.10% and/or one or more out of Mn; 0.20W1.0%, Cr; 0.05W 0.30%, Zr; 0.05W0.30% and Ti; 0.02W0.20%. Since the alloy has strength at its deposited part about comparable to that at its base metal as well as superior ductility and stress corrosion cracking resistance, it is suitable for use as hollow extruded shapes. COPYRIGHT: (C)1979,JPO&Japio