Showing papers on "Stress corrosion cracking published in 1996"

Quantitative Prediction of Environmentally Assisted Cracking

Abstract: It has long been recognized that the stress corrosion cracking (SCC) and corrosion fatigue cracking susceptibility of various alloy and environment systems is dependent upon complex interactions between stress, material, and environmental parameters. This complexity can lead to scatter in cracking responses that, in turn, leads to difficulty in predicting the life of engineering structures. F.P. Ford was the 1995 recipient of the W.R. Whitney Award sponsored by NACE International. The present work is taken from his award lecture at CORROSION/95 held in March 1995 in Orlando, Florida. His lecture focused on how these interactions may be predicted quantitatively for ductile alloys in aqueous environments with knowledge of the cracking mechanism. This capability may lead to life prediction of critical structures in, for instance, boiling-water nuclear reactors (BWR).

Models of High‐Temperature, Environmentally Assisted Embrittlement in Ceramic‐Matrix Composites

Abstract: The intermediate-temperature oxidation embrittlement, or pest, effect found in ceramic-matrix composites (CMCs) is shown to have features analogous to stress corrosion cracking. The behavior involves crack growth upon oxidation of the fibers or the fiber coatings to form an oxide that weakens the fibers. It has reaction- and diffusion-controlled regimes. The former occurs at low stresses. The latter occurs at higher stresses. It is controlled by oxygen ingress through the matrix cracks. There is also a crack growth threshold. Expressions for the crack velocity above the threshold are derived as well as the stress dependence of the rupture life.

Mechanistic Aspects of Intergranular Stress Corrosion Cracking of Ferritic Steels

Abstract: Evidence of intergranular attack (IGA) in the absence of stress, together with dissolution kinetics, indicates that intergranular stress corrosion cracking (IGSCC) of ferritic steels in va...

Structure, chemistry, and stress corrosion cracking of grain boundaries in alloys 600 and 690

Abstract: The microstructure in six commercial batches of alloys 600 and 690 has been investigated using scanning electron microscopy (SEM), analytical transmission electron microscopy (ATEM), atom probe field ion microscopy (APFIM), and secondary ion mass spectroscopy (SIMS). The materials were also tested with respect to their resistance to intergranular stress corrosion cracking (IGSCC) in high-purity water at 365 °. Applied microanalytical techniques allowed direct measurement of carbon concentration in the matrix together with determination of grain boundary micro structure and microchemistry in all material conditions. The distribution of oxygen near a crack in material tested with respect to IGSCC was also investigated. The role of carbon and chromium and intergranular precipitates on IGSCC is discussed.

Initiation of stress corrosion cracking for pipeline steels in a carbonate-bicarbonate solution

Abstract: The linearly increasing stress test (LIST) was used to study the stress corrosion cracking (SCC) behavior of a range of pipeline steels in carbonate-bicarbonate solution under stress rate control at different applied potentials. Stress corrosion cracking, at potentials below -800 mV(SCE), was attributed to hydrogen embrittlement. Stress corrosion cracking, in the potential range from about-700 to -500 mV(SCE), was attributed to an anodic dissolution mechanism. In the anodic potential region, the SCC initiation stress was larger than the yield stress and was associated with significant plastic deformation at the cracking site. The relative SCC initiation resistance decreased with in-creasing yield strength. In the cathodic potential region, the SCC initiation stress was smaller than the yield stress of steel; it was approximately equal to the stress at 0.1 pct strain(@#@ Σ0.1pct) for all the steels. The original surface was more susceptible to SCC initiation than the polished surface.

Theoretical Estimation of Crack Growth Rates in Type 304 Stainless Steel in Boiling-Water Reactor Coolant Environments

Abstract: The coupled-environment fracture model (CEFM)for intergranular stress corrosion cracking (IGSCC) of sensitized type 304 (UNS S30400) stainless steel (SS) in light-water reactor (LWR) heat-...

Residual Stress Measurement in Steel Plates and Welds Using Critically Refracted Longitudinal (LCR) Waves

Abstract: The application of acoustoelasticity using critically refracted longitudinal (LCR) waves is described for measuring residual stress in welded steel plates. Residual stresses are self-equilibrating and may exist in a material that has been deformed in a nonhomogeneous manner. When unknown residual stress is present in a structure, the true stress may become significantly greater than the working stress. In a corrosive environment, highly stressed areas that have not been properly stress relieved are prone to stress corrosion cracking. Areas near welds are particularly susceptible to stress corrosion cracking. Two welded plates were investigated for the present work: one hot-rolled and the other cold-rolled. Residual stresses are usually greatest after welding. Further, longitudinal stress (i.e., stress parallel to the weld bead) is typically greater than the component transverse to the weld bead. Since the acoustoelastic behavior of the LCR wave is largest when propagated parallel to a uniaxial st...

Current applications of x-ray diffraction residual stress measurement

Abstract: A brief theoretical development of x-ray diffraction residual stress measurement is presented emphasizing practical engineering applications of the plane-stress model, which requires no external standard Determination of the full stress tensor is briefly described, and alternate mechanical, magnetic, and ultrasonic methods of residual stress measurement are compared Sources of error arising in practical application are described Subsurface measurement is shown to be necessary to accurately determine the stress distributions produced by surface finishing such as machining, grinding, and shot peening, including corrections for penetration of the x-ray beam and layer removal Current applications of line broadening for the prediction of material property gradients such as yield strength in machined and shot peened surfaces, and hardness in steels are presented The development of models for the prediction of thermal, cyclic, and overload residual stress relaxation are described X-RAY DIFFRACTION (XRD) STRESS MEASUREMENT can be a powerful tool for failure analysis or process development studies Quantifying the residual stresses present in a component, which may either accelerate or arrest fatigue or stress corrosion cracking, is frequently crucial to understanding the cause of failure Successful machining, grinding, shot peening, or heat treatment may hinge upon achieving not only the appropriate surface finish, dimensions, case depth or hardness, but also a residual stress distribution producing the longest component life The engineer engaged in such studies can benefit by an understanding of the limitations and applications of XRD stress measurement This paper presents a brief development of the theory and sources of error, and describes recent applications of material property prediction and residual stress relaxation Application of XRD stress measurement to practical engineering problems began in the early 1950's The advent of x-ray diffractometers and the development of the plane-stress residual stress model allowed successful application to hardened steels (1,2) The development of commercial diffractometers and the work of the Fatigue Design and Evaluation Committee of the SAE (3) resulted in widespread application in the automotive and bearing industries in the 1960's By the late 1970's XRD residual stress measurement was routinely applied in aerospace and nuclear applications involving fatigue and stress corrosion cracking of nickel and titanium alloys, as well as aluminum and steels Today, measurements are routinely performed in ceramic, intermetallic, composite, and virtually any fine grained crystalline material A variety of position sensitive detector instruments allow measurement in the field and on massive structures The theoretical basis has been expanded to allow determination of the full stress tensor, with certain limitations

In-situ palladium doping or coating of stainless steel surfaces

Abstract: A method for reducing corrosion of metal components in a water-cooled nuclear reactor. A compound containing a platinum group metal, e.g. palladium, is injected alone in small amounts into the high temperature water of the reactor in the form of a solution or suspension. This compound decomposes under reactor thermal conditions to release atoms of the metal in an amount sufficient when present on the metal components to reduce the electrochemical corrosion potential of the metal components to a level below the critical potential to protect against intergranular stress corrosion cracking.

X-Ray Study on Deformation and Fracture of Solid. Effects of Water Jet Peening on Corrosion Resistance and Fatigue Strength of Type 304 Stainless Steel.

Abstract: The effect of water jet peening (WJP) on the improvement of stress corrosion cracking (SCC) and fatigue strength was verified by performing SCC and fatigue tests. The SCC specimens employed were sensitized type 304 stainless steel simulating the heat affected zone in welded metal. The creviced bent beam (CBB) type SCC test was performed in high temperature water using the smooth and pre-cracked specimens. WJP remarkably improved the susceptibility of SCC for the smooth specimen, and cracks were not initiated when the applied strain was less than 0.3%. WJP was also confirmed to prevent SCC for the pre-cracked specimen. In the fatigue tests both smooth and pre-cracked plate specimens were subjected to cyclic bending loads in air at room temperature. The fatigue strength of smooth and pre-cracked specimens at a fatigue life of 107 cycles was increased by 1.1 and 2.4 times, respectively, in comparison with that of non-WJP specimens. This means that WJP was much more effective for the pre-cracked specimens. CBB and fatigue tests show that WJP is an effective technique for preventing SCC in the structural components of power plants.

Localized surface plasticity during stress corrosion cracking

Abstract: A previously proposed stress corrosion cracking (SCC) mechanism incorporating localized surface plasticity (LSP), crack initiation, and crack-tip embrittlement by anodic dissolution at film rupture sites is reviewed, together with new information supporting the mechanism. Externally imposed anodic dissolution currents increase creep rates of pure metals and alloys. Creep prior to SCC has been observed frequently and may result from anodic currents at active film rupture sites caused by coupling to surrounding noble passive surfaces. Recently revealed correlations between creep rate and SCC failure times imply that mechanisms of creep and cracking may be related. Anodic attenuation of strain hardening at film rupture sites may cause LSP, leading to triaxial stress conditions, suppressed slip, and crack initiation. Recent thin-film diffusion experiments show evidence of vacancy formation at anodically dissolving Cu surfaces. It has been suggested that anodically generated vacancies may increase creep and plasticity by stimulation of dislocation climb or by attraction to dislocation cores. Point-defect vacancies may weaken the crystal lattice, as do point-defect H atoms in the decohesion mechanism popular for explaining hydrogen embrittlement (HE).

Effect of hydrogen in aluminium and aluminium alloys: A review

Abstract: Susceptibility of aluminium and its alloys towards hydrogen embrittlement has been well established. Still a lot of confusion exists on the question of transport of hydrogen and its possible role in stress corrosion cracking. This paper reviews some of the fundamental properties of hydrogen in aluminium and its alloys and its effect on mechanical properties. The importance of hydrogen embrittlement over anodic dissolution to explain the stress corrosion cracking mechanism of these alloys is also examined in considerable detail. The various experimental findings concerning the link between hydrogen embrittlement and stress corrosion cracking are also discussed.

Effect of Solution Composition and Electrochemical Potential on Stress Corrosion Cracking of X-52 Pipeline Steel

Abstract: Electrochemical measurements and constant extension rate tests (CERT) of cold-worked X-52 carbon steel showed stress corrosion cracking (SCC) can be induced in aqueous sulfate (SO42−), bic...

Method and system for detection and prevention of stress corrosion cracking in buried structures

Abstract: A method and system for detecting and preventing Stress Corrosion Cracking (SCC) in buried pipelines or other structures is presented. The basic principle of the invention is to use a plurality of test coupons which are placed in the same environment as a pipeline or other structure of interest as indicators of the development of SCC in the structure of interest. Loading and temperature of the test coupons are controlled. The test coupons are given a range of different Cathodic Protection (CP) levels, with the range of CP levels selected so as to encompass the CP level at which SCC would be expected to occur. The occurrence of cracking in a test coupon indicates levels of CP which will sustain SCC. SCC is prevented in the structure by application of a level of CP which did not sustain SCC.

Chloride-Induced Stress Corrosion Cracking of Powder Metallurgy Duplex Stainless Steels

Abstract: The chloride-induced stress corrosion cracking (SCC) resistance of nitrogen-alloyed, powder metallurgically (P/M) produced and hot isostatically pressed (HIP) duplex stainless steels (DSS)...

Effect of Zinc Additions on Oxide Rupture Strain and Repassivation Kinetics of Iron-Based Alloys in 288°C Water

Abstract: The effect of Zn water chemistry additions on the mechanism of intergranular stress corrosion cracking (IGSCC) of Fe-based alloys in water at 288°C was evaluated in terms of the slip-disso...

Method for developing residual compressive stress in stainless steel and nickel base superalloys

Abstract: Compressive residual stresses can be developed by underwater plasma transferred arc welding. The development of these compressive stresses act to prevent hot cracking and He embrittlement that can develop during welding or stress corrosion cracking that can develop subsequent to the welding operation.

Technical Note: Relationship Between Electrical Conductivity and Stress Corrosion Cracking Susceptibility of Al 7075 and Al 7475 Alloys

Abstract: A relationship between electrical conductivity and stress corrosion cracking (SCC) resistance of the 7,000-series Al-Zn-Mg alloys has been established, although only from the near-peak strength T6 temper to the overaged T73 tempered condition. The present work investigated whether this relationship exists for all periods of aging and for Al alloys with different compositions and grain structures.

Environment-induced deformation localization during transgranular stress corrosion cracking

Abstract: The nucleation and evolution of deformation patterns occurring during transgranular stress corrosion cracking (TGSCC) were studied in an attempt to produce new alternatives for addressing the nature of the embrittlement process. Flat, tensile α-brass (72% Cu-28% Zn) specimens were tested in 5 M aqueous ammonia (NH4OH) solution at a strain rate of 1 × 10−5/s. Slip-band spacing (SBS) and slip-band height (SBH) were measured as a function of strain by conducting interrupted experiments in the SCC environment and were compared with those developed during laboratory air experiments. The presence of the TGSCC-causing environment during straining promoted localized plastic deformation at the near-surface region and, more importantly, produced an entirely different deformation pattern from that developed in laboratory air. The deformation evolved in the presence of the TGSCC electrolyte was highly localized, exhibiting small SBS but large SBH. Also, a periodicity was exhibited by the crack initiation pro...