Predicting Susceptibility of Alloy 600 to Intergranular Stress Corrosion Cracking Using a Modified Electrochemical Potentiokinetic Reactivation Test

Ahn, MyoungKi; Kwon, Hyuk‐Sang; Lee, J.-H.

doi:10.5006/1.3293610

Cited by 42 publications

(16 citation statements)

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“…He shows that WEDM process has proved its adequacy to machine Inconel 601 material under acceptable conditions 2. Some previous work reported on the oxidation behavior of alloy 600 (containing more nickel, less chromium, and less aluminum compared to alloy 601) 3–5 but not so much work has been performed yet concerning the oxidation properties of the Inconel 601 alloy at high temperatures. Nevertheless, this alloy has been tested in aqueous corrosion conditions 6 due to the fact that heat treatment at 700 °C can be responsible for an increase in corrosion intensity after sensitization acting on the alloy grain size.…”

Section: Introductionmentioning

confidence: 99%

Oxidation mechanism of the Inconel 601 alloy at high temperatures

Buscail¹,

Perrier²,

Josse

2011

Materials & Corrosion

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The Inconel 601 alloy oxidation was performed in air, in the temperature range 1000-1150 8C, during 90 h. Kinetic results show that the parabolic behavior is always followed in this temperature range. The Arrhenius plot of the k p values shows two different activation energies. Between 1000 and 1050 8C the activation energy is E a1 ¼ 160 AE 10 kJ/mol. In the 1050-1150 8C temperature range a higher value is calculated E a2 ¼ 252 AE 20 kJ/mol. The E a2 value and the X-ray diffraction (XRD) results and scanning electron microscope (SEM) energy dispersive X-ray spectroscopy (EDS) examinations are in accordance with a scale growth mechanism limited by a growing Cr 2 O 3 scale acting as a diffusion barrier. In the 1000-1050 8C temperature range the activation energy is lower and the structural analyses show that the oxide scale is not only composed of Cr 2 O 3 . Then, the oxide scale is composed of titanium oxides (TiO 2 and Ti 2 Cr 7 O 17 ) and chromia mixed together. A doping effect of the chromia scale by titanium can be envisaged. Our results also show the presence of some Mn 1.5 Cr 1.5 O 4 at the external interface. This external subscale spalls off easily during cooling after the highest temperature oxidation tests. Nevertheless, XRD results and SEM-EDS observations show that the Cr 2 O 3 scale remains very adherent on the substrate and can give a good oxidation protection. This good adherence can be related to the presence of a low amount of aluminum in the Inconel 601 alloy composition.

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Section: Introductionmentioning

confidence: 99%

Oxidation mechanism of the Inconel 601 alloy at high temperatures

Buscail¹,

Perrier²,

Josse

2011

Materials & Corrosion

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“…IGSCC susceptibility of SS in various environments was found to correlate with the minimum chromium level in the depletion regions along grain boundaries. [52][53][54][55] Others did observe a good correlation between EPR-DOS of SS sensitized at constant temperature for varying times with IGSCC, but they observed a poor correlation when specimens were sensitized at different temperatures at constant time. 48 Nonunanimous fi ndings on the relationship between DOS and IGSCC could be due the fact that which parameter (such as chromium-depleted width, minimum chromium level, or both) of the chromium-depleted region that the DOS follows is not clear.…”

Section: Introductionmentioning

confidence: 89%

Effects of Cold Deformation Prior to Sensitization on Intergranular Stress Corrosion Cracking of Stainless Steel

Singh¹,

Swaminathan²,

Das³

et al. 2005

CORROSION

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The effects of deformation, prior to sensitization, on intergranular stress corrosion cracking (IGSCC) were studied on the AISI 304 (UNS S30400) stainless steel (SS). The degree of sensitization (DOS) was quantifi ed by the double loop electrochemical potentiokinetic reactivation (DL-EPR) method. The susceptibility to IGSCC was investigated by the slow strain rate test (SSRT) carried out in polythionic acid (PTA) solutions. The results were complemented by scanning electron microscopy (SEM) fractographs. Deformation was found to accelerate sensitization, and a peak in sensitization vs. deformation was always observed. This peak was found to shift toward lower deformations with an increase in sensitization temperature. At 700°C, prior deformation is able to desensitize or heal the SS after 24 h. IGSCC was observed in AISI 304 SS after some treatments. No one-to-one correspondence was observed between IGSCC and DOS; this could be explained by the fact that the DOS measured by the DL-EPR indicates the depleted regions below ~15% Cr, whereas IGSCC depends on the availability of continuous grain boundary paths that are chromium-depleted, along with strain rate and environment (pH, temperature, etc.). Deformation prior to sensitization causes carbide formation and chromium depletion to occur near dislocations within the grain interiors, in addition to along grain boundaries. The DOS does not differentiate between these interior regions and the grain boundary regions, and shows a total value accounted for chromium depletion. However, IGSCC occurs only when there is chromium depletion along grain boundaries and therefore these intragrain regions further reduce the correlation between the DOS and IGSCC susceptibility. Deformation close to or beyond 60% was found to prevent IGSCC of AISI 304 SS, irrespective of the sensitization temperature or DOS value.

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“…1(c) and 3(c)). Was et al [10] found, from Heuy and Streicher tests, that severe IGA occurred when the measured Cr concentration on the grain boundary was below 9 wt% with a nearly continuous distribution of grain boundary Cr-rich carbides. Therefore, the LSM+SEN Alloy 600 should have a high resistance to IGA in acidic environments.…”

Section: Discussionmentioning

confidence: 99%

Double loop electrochemical potentiokinetic reactivation test of Nickel-base Alloy 600 surface-melted by a CO2 laser beam

Lim

et al. 2001

Met. Mater. Int.

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Ni-base Alloy 600 has been widely used as a steam generator (S/G) tubing material in nuclear power plants because of its good mechanical and corrosion properties at high temperatures. However, degradations of S/G tubes due to intergranular attack (IGA) and intergranular stress corrosion cracking (IGSCC) during normal operation have been frequently reported. In particular, Alloy 600 can be very susceptible to IGA/IGSCC in some sulfur-bearing environments by sensitization. In this paper, the beneficial effects of laser surface melting (LSM) on intergranular corrosion of the sensitized Alloy 600 is presented from the results of the double loop electrochemical potentiokinetic reactivation (DL-EPR) test. The DL-EPR test was performed in de-aerated 0.01 M H 2 SO 4 +20 ppm KSCN at a scan rate of 0.5 mV/sec at room temperature. The degree of sensitization (DOS) of the sensitized Alloy 600 measured from the DL-EPR test was considerably reduced by LSM. The sensitized Alloy 600 after LSM also exhibited a relatively low DOS, compared with that of the sensitized but not laser treated Alloy 600. From the microscopic observation, it was found that the microstructural changes brought about by the LSM process, especially changes in the precipitation behavior of grain boundary Cr-rich carbides, caused the improvement of resistance to intergranular corrosion of the laser treated Alloy 600. The resistance to IGSCC of the laser treated Alloy 600 in sulfur-bearing environments was also discussed from the results of measured DOS and microstructural examination.

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Predicting Susceptibility of Alloy 600 to Intergranular Stress Corrosion Cracking Using a Modified Electrochemical Potentiokinetic Reactivation Test

Cited by 42 publications

References 0 publications

Oxidation mechanism of the Inconel 601 alloy at high temperatures

Oxidation mechanism of the Inconel 601 alloy at high temperatures

Effects of Cold Deformation Prior to Sensitization on Intergranular Stress Corrosion Cracking of Stainless Steel

Double loop electrochemical potentiokinetic reactivation test of Nickel-base Alloy 600 surface-melted by a CO2 laser beam

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