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Models slip-dissolution

R.W. Staehle, Predictions and experimental verification of the slip dissolution model for stress corrosion cracking of low strength alloys, in R.W. Staehle (Ed.), Stress Corrosion Cracking and Hydrogen Embrittlemen of Iron Base Alloys, In NACE-5NACE, Houston, TX, 1977, pp. 180-207. [Pg.447]

F ure 11.41 Slip-dissolution model of stress corrosion cracking. Due to slip, the metal unprotected by the passive film enters into contact with the electrolyte, thus allowing active dissolution at the crack tip for a certain period of time. [Pg.499]

The slip dissolution model assumes that plastic deformation at the crack tip is responsible for the activation. But other mechanisms can have the same effect. Tensile stress at the crack tip could, for example, break a brittle tarnish film or passive oxide film, thereby exposing the base metal to the electrolyte. Selective dissolution of alloy components at the crack tip could locally weaken the metal matrix and thus permit... [Pg.500]

Limitations of the Film Rupture-Slip Dissolution Model. 250... [Pg.208]

In many systems, such as Alloy 600 in caustic solutions [Fig. 5-19 (Combrade and Scott, 1997)], the film repair kinetics, characterized by the parameter Q, exhibit good correlation with the SCC behavior. This parameter is at the root of the so-called film rupture-slip dissolution" model which may be considered as the simplest kind of corrosion-deformation interaction that can result in SCC (but also in localized corrosion). [Pg.225]

The SCC mechanisms presented in the following sections are those that are presently considered to have the greatest interest from a mechanistic point of view, or, in the case of the slip dissolution model, to give some quantitative prediction, at least in specific cases. [Pg.245]

The film rupture/slip dissolution model has been proposed for many systems, including stainless steels in chloride solutions, Fe-Ni-Cr steels, low alloy steels, and mild steel in caustic environments, etc. But the see and eF of sensitized stainless steel in BWR nuclear plants is probably the most... [Pg.248]

SCC data are presented as velocity versus static stress parameter such as K, yet it is the dynamic plasticity at the crack tip that actually features the newly formed oxide film [67,113], This problem was considered by Vermilyea [24], who showed that under a static stress the corrosion process could advance the crack tip into a region that had reached an equilibrium distribution of plastic strain (e ), and produce a strain transient (Ae I that could fracture a newly formed oxide (Fig. 23). Later Sieradzki [44] showed that the depth of transient corrosion required in Vermilyea s original model was um-easonably large ( tm), confirming that static slip-dissolution models can apply only to intergranular SCC, where there is a directional active path with a very low repassivation rate [33]. It is not clear how the shielding of the crack... [Pg.420]

Figure 22 Anodic current decays for Fe, Fe-3Ni-2Mo, and an Fe-lOP amorphous alloy (simulating a grain boundary) in 9 M NaOH solution at 98°C and 00 mV (Hg-HgO) [85], The original i(t) decays have been converted into q(f) (charge density versus time) and then into for comparison with a slip-dissolution model of SCC where the crack velocity is proportional to q(z)/z with x being the interval between film mptnre events at the crack tip. The indicated crack velocities measured for Fe-Ni-Mo and Fe-Ni-P alloys are consistent with a single valne of x(6 3 s), giving some vahdity to the use of a simulated grain boundary alloy. Figure 22 Anodic current decays for Fe, Fe-3Ni-2Mo, and an Fe-lOP amorphous alloy (simulating a grain boundary) in 9 M NaOH solution at 98°C and 00 mV (Hg-HgO) [85], The original i(t) decays have been converted into q(f) (charge density versus time) and then into for comparison with a slip-dissolution model of SCC where the crack velocity is proportional to q(z)/z with x being the interval between film mptnre events at the crack tip. The indicated crack velocities measured for Fe-Ni-Mo and Fe-Ni-P alloys are consistent with a single valne of x(6 3 s), giving some vahdity to the use of a simulated grain boundary alloy.
The film rupture interval t decreases with increasing strain rate until eventually / = and V approaches the maximum or region II velocity Uq. For cyclic loads or slow strain rate tests, is relatively easy to estimate, and one can test the slip-dissolution model as a function of strain rate and potential [30-33], More generally, one can include a continuum version of Vermilyea s concept [114] ... [Pg.422]

Wg. Historically, this is an important issue, as these concerns were partly responsible for the abandonment of the slip-dissolution model by Galvele [20,118],... [Pg.425]

This localized dissolution process is not easy to take into account in numerical modeling of crack propagation. The slip dissolution model for CF is based on the fact that for many alloys in different solutions the crack propagation rate is proportional to the oxidation kinetics. Thus, by invoking Faraday s law, the average environmentally controlled crack propagation rate for passive alloys is related to oxidation charge density passed between film rupture events, Qf. [Pg.465]

Experimentally validated elements of these earlier proposals have been incorporated in the current slip dissolution model, which relates the crack propagation to the oxidation that occurs w hen the protective film at the crack tip is ruptured [39-44], Different types of protective films have been proposed, including oxides, mixed oxides, salts, or noble metals left on the surface after selective dissolution of a more active component in the alloy. As discussed below, quantitative predictions of the crack propagation rate via the slip dissolution mechanism are based on the faradaic relationship between the oxidation charge density on a surface and the amount of metal transformed from the metallic state to the oxidized state (e g., MO or M ). [Pg.610]

Figure 5 Illustration of the strain rate dependence of the crack propagation rate due to the slip dissolution model, and the additive properties of the mechanical and environmental components of crack advance during corrosion fatigue. Figure 5 Illustration of the strain rate dependence of the crack propagation rate due to the slip dissolution model, and the additive properties of the mechanical and environmental components of crack advance during corrosion fatigue.
Figure 6 Schematic illustration of the elements of the film induced cleavage mechanism of crack propagation [1], Note similarity to the slip dissolution model (Fig. 5) during initial stages of propagation cycle. Figure 6 Schematic illustration of the elements of the film induced cleavage mechanism of crack propagation [1], Note similarity to the slip dissolution model (Fig. 5) during initial stages of propagation cycle.
BWR environments) in which it is assumed [1] that the slip dissolution model is a reasonable working hypothesis for the crack propagation mechanism. This baseline prediction methodology is then extended to treat the effects of irradiation on the cracking of stainless steel. Further extension to other alloys (e.g., nickel-base, low-alloy steels) and environments (PWR) is also outlined. [Pg.617]

It is assumed that the slip dissolution model is applicable to transgranular environmentally assisted cracking in the A533B/A508 low-alloy steel-water system at 288°C [1]. It is recognized that this assumption may introduce a systematie error due... [Pg.627]

Values of 0 at least 10 times those obtained in static tests are readily achieved in a slow strain rate test, with a large corresponding decrease in the IR potential drop or crack tip metal cation concentration for a given value of i,. Such arguments show that concerns about the saturation of metal ions or very high IR potential drops within cracks are unfounded for slow strain rate tests, even if there is no active path w. Historically, this is an important issue, as these concerns were partly responsible for the abandonment of the slip-dissolution model by Galvele [20,118]. [Pg.521]

The mechanism of chloride-SCC of austenitic stainless steels is still debatable. We may discount the slip-dissolution model for crack growth at 80°C [68] the required anodic... [Pg.523]


See other pages where Models slip-dissolution is mentioned: [Pg.1157]    [Pg.445]    [Pg.446]    [Pg.83]    [Pg.157]    [Pg.500]    [Pg.1190]    [Pg.208]    [Pg.246]    [Pg.250]    [Pg.261]    [Pg.540]    [Pg.545]    [Pg.400]    [Pg.426]    [Pg.438]    [Pg.609]    [Pg.612]    [Pg.637]    [Pg.499]    [Pg.500]    [Pg.517]    [Pg.517]    [Pg.533]   
See also in sourсe #XX -- [ Pg.500 , Pg.523 ]




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