Optimization of the Double Loop Electrochemical Potentiokinetic Reactivation Method for Detecting Sensitization of Nickel Alloy 690

CORROSION ◽  
10.5006/2562 ◽  
2017 ◽  
Vol 74 (2) ◽  
pp. 210-224 ◽  
Author(s):  
Magalí E. Gonzalez ◽  
Mariano A. Kappes ◽  
Martín A. Rodríguez ◽  
Patricia Bozzano ◽  
Ricardo M. Carranza ◽  
...  
Keyword(s):  
Nickel Alloy ◽  
Nuclear Power ◽  
Potassium Thiocyanate ◽  
Double Loop ◽  
Chromium Depletion ◽  
Epr Method ◽  
Transmission Electron ◽  
Alloy 690 ◽  
Electrochemical Potentiokinetic Reactivation ◽  
Epr Test

Nickel alloy 690 (UNS N06690) is one of the current choices for nuclear power plant steam generator tubing. The severity of certain stress corrosion cracking submodes in Ni-Cr-Fe alloys, such as Alloy 690, may be a function of the alloy sensitization condition. Sensitization results from chromium carbide precipitation at or near grain boundaries when the alloy is exposed to temperatures from 500°C to 800°C, which causes local chromium depletion in the adjacent matrix. The objective of this work was to study the parameters that control the double loop electrochemical potentiokinetic reactivation (DL-EPR) method and to develop an optimized test routine for Alloy 690. Alloy 690 specimens were tested under different thermal treatments, tailored to obtain a variety of concentrations of chromium in solid solution near the grain boundary (GB) region. The DL-EPR method was applied to Alloy 690 in solutions with different concentrations of sulfuric acid and potassium thiocyanate, at 30°C and 50°C. The optimal condition for detecting sensitization of Alloy 690 was 0.5 M H2SO4 + 0.001 M KSCN, at 30°C. Optical micrographs confirmed an intergranular type of attack under thermally aged (sensitized) conditions. The ratio of the reactivation to the activation peak intensities (Ir/Ia) obtained in the DL-EPR test agreed well with mass loss obtained in boiling nitric acid solution with Cr(VI) additions (modified Huey test). Chromium depletion profiles near the GB of thermally treated specimens under different conditions were measured with the energy dispersive x-ray spectroscopy technique, performed on a transmission electron microscope. A model available in the literature was fitted to those results. The Ir/Ia ratio for Alloy 690, obtained when using the optimal DL-EPR testing conditions, correlated well with the Cr depletion zone width and depth near the GB.

Evaluation of the Susceptibility to Intergranular Corrosion for a Novel Cr-Mn-N Austenitic Stainless Steel Using DL-EPR

2013 ◽  
Vol 631-632 ◽  
pp. 192-197
Author(s):  
Lei Gang Zheng ◽  
Xiao Qiang Hu ◽  
Xiu Hong Kang ◽  
Dian Zhong Li
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Electrolyte Solution ◽  
Intergranular Corrosion ◽  
Xrd Analysis ◽  
Double Loop ◽  
Chromium Depletion ◽  
Electrochemical Potentiokinetic Reactivation ◽  
Epr Test ◽  
Optical Micrographs

The sensitization and intergranular corrosion (IGC) behavior of a novel Cr-Mn-N austenitic stainless steel (named as MPMD133) sensitized in the temperature range from 600 oC to 1000oC for 3 hours was investigated by the double loop electrochemical potentiokinetic reactivation (DL-EPR) test. The effects of the sensitization temperature on the susceptibility to IGC of MPMD133 were examined in the 0.5M H2SO4 +0.01M KSCN electrolyte solution. The results show that the degree of IGC increases as the sensitization temperature increasing till 900oC. Meanwhile it decreases rapidly when the sensitization temperature is elevated up to 1000oC, which is confirmed by the subsequent optical micrographs observation. The XRD analysis reveals that the precipitation of Cr23C6 leads to chromium depletion along the grain boundaries, consequently results in the susceptibility to IGC.

Assessment of Thermal Aging of Austenitic Stainless Steel Weld Metal by Using the Double Loop Electrochemical Potentiokinetic Reactivation Technique

CORROSION ◽  
10.5006/2902 ◽  
2019 ◽  
Vol 75 (4) ◽  
pp. 377-388 ◽  
Author(s):  
Xiaodong Lin ◽  
Qunjia Peng ◽  
En-Hou Han ◽  
Wei Ke
Keyword(s):  
Stainless Steel ◽  
Weld Metal ◽  
Thermal Aging ◽  
Double Loop ◽  
Steel Weld ◽  
Stainless Steel Weld ◽  
Steel Weld Metal ◽  
Electrochemical Potentiokinetic Reactivation ◽  
Stainless Steel Weld Metal ◽  
Epr Test

Double loop electrochemical potentiokinetic reactivation (DL-EPR) was applied to evaluate thermal aging of 308L stainless steel weld metal. It was found that the activation and reactivation peaks of DL-EPR curve were induced by dissolution of austenite and δ-ferrite, respectively. Before saturation of hardness, the linear relationship between reactivation ratio and hardness could be used for assessing the thermal aging-induced hardening. In the following thermal aging process, the reactivation ratio is applicable to assess the occurrence of the saturation of thermal aging-induced hardening. The results demonstrated that the DL-EPR test is applicable to assess the evolution of thermal aging.

scholarly journals Interlaboratory Testing to Assess Repeatability and Reproducibility of the Double Loop Electrochemical Potentiokinetic Reactivation (DL-EPR) Tests for Type 304H Stainless Steels

CORROSION ◽  
10.5006/3559 ◽  
2020 ◽  
Vol 76 (8) ◽  
pp. 742-749
Author(s):  
Raul B. Rebak ◽  
Sheldon W. Dean
Keyword(s):  
Stainless Steels ◽  
Industrial Applications ◽  
Double Loop ◽  
Degree Of Sensitization ◽  
Electrochemical Potentiokinetic Reactivation ◽  
Degree Of Confidence ◽  
Repeatability And Reproducibility ◽  
Epr Test ◽  
High Degree ◽  
Interlaboratory Testing

The sensitization of stainless steels may decrease their corrosion resistance in industrial applications. Traditional immersion tests exist to determine the degree of sensitization (DOS) of the stainless steels. However, electrochemical methods may be preferred because they are less expensive and faster to perform. The fast and robust double loop electrochemical potentiokinetic reactivation (DL-EPR) test has been introduced to the corrosion community some decades ago but an interlaboratory testing study was necessary to assess the repeatability and reproducibility of the DOS results. This work reports on a recent study where 11 laboratories returned results that show a high degree of confidence in the data obtained by DL-EPR.

scholarly journals On the Role of Grain Size and Carbon Content on the Sensitization and Desensitization Behavior of 301 Austenitic Stainless Steel

Metals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1193 ◽  
Author(s):  
Kolli ◽  
Javaheri ◽  
Kömi ◽  
Porter
Keyword(s):  
Grain Size ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Grain Boundary ◽  
Carbon Content ◽  
Double Loop ◽  
Boundary Carbide ◽  
Self Healing ◽  
Chromium Depletion ◽  
Electrochemical Potentiokinetic Reactivation

The effect of grain size in the range 72 to 190 μm and carbon content in the range 0.105–0.073 wt.% on the intergranular corrosion of the austenitic stainless steel 301 has been investigated. Grain boundary chromium depletion has been studied directly using energy dispersive X-ray spectroscopy combined with scanning transmission electron microscopy and indirectly using double loop electrochemical potentiokinetic reactivation tests. In addition, chromium depletion has been modelled using the CALPHAD Thermo-Calc software TC-DICTRA. It is shown that the degree of sensitization measured using the double loop electrochemical potentiokinetic reactivation tests can be successfully predicted with the aid of a depletion parameter based on the modelled chromium depletion profiles for heat treatment times covering both the sensitization and de-sensitization or self-healing. Additionally, along with intergranular M23C6 carbides, intragranular M23C6 and Cr2N nitrides that affect the available Cr for grain boundary carbide precipitation were also observed.

Friction Stir Welding: Mitigating the Susceptibility to Intergranular Corrosion of Alloy 625

2021 ◽  
Author(s):  
Guilherme Vieira Braga Lemos ◽  
Alexandre Bellegard Farina ◽  
Henrique Piaggio ◽  
Luciano Bergmann ◽  
Jane Zoppas ◽  
...  
Keyword(s):  
Friction Stir Welding ◽  
Intergranular Corrosion ◽  
Double Loop ◽  
Tool Rotational Speed ◽  
Alloy 625 ◽  
Friction Stir ◽  
Degree Of Sensitization ◽  
Electrochemical Potentiokinetic Reactivation ◽  
The Mean ◽  
Epr Test

Abstract In this work, friction stir welding (FSW) was employed to alloy 625 grade I (soft annealed) sheets. Therefore, solid-state based welding was undertaken with a tool rotational speed of 200 rpm and welding speed of 1 mm/s. Microstructural features were analyzed by light optical and scanning electron microscopy (SEM). Moreover, microhardness measurements were performed. The susceptibility to intergranular corrosion was verified by the double-loop electrochemical potentiokinetic reactivation (DL-EPR) test. Complementary, intergranular corrosion was evaluated by ASTM G28 Method A. FSW promoted grain refinement, increased microhardness, and reduction in the degree of sensitization. Finally, the mean corrosion rate observed in the ASTM G28A test was 0.4406 mm/year, which suggests a good weld quality.

scholarly journals Intergranular Corrosion of Low Cr Ferritic Stainless Steel 429 Evaluated by the Optimized Double Loop Electrochemical Potentiokinetic Reactivation Test

2015 ◽  
Vol 2015 ◽  
pp. 1-10
Author(s):  
Xiao-lei Li ◽  
Yi-fan Ni ◽  
Yi-ming Jiang ◽  
Jin Li ◽  
Li Li
Keyword(s):  
Stainless Steel ◽  
Ferritic Stainless Steel ◽  
Intergranular Corrosion ◽  
Aging Treatment ◽  
Double Loop ◽  
Depletion Zone ◽  
Scanning Rate ◽  
Microstructure Observation ◽  
Electrochemical Potentiokinetic Reactivation ◽  
Epr Test

Intergranular corrosion (IGC) of Nb-Ti stabilized ferritic stainless steel (FSS) 429 was investigated using the double loop electrochemical potentiokinetic reactivation (DL-EPR) test combined with the microstructure observation. The results indicated that the optimized DL-EPR test condition for FSS 429 was the solution of 0.5 M H2SO4+ 0.0001 M KSCN with a scanning rate of 100 mV/min at 30°C. Based on this condition, the specimens aging at 400–700°C for different duration were tested and a time-temperature-sensitization (TTS) curve for FSS 429 was obtained, which reveals the sensitization nose was located around 550°C. The criticalIr/Iavalue was determined to be about 3% above which IGC occurred. After aging treatment, Cr depletion zone was detected using energy dispersive spectroscopy (EDS), most possibly due to Cr segregation around intergranular TiC and NbC.

Detecting Intergranular Phases in UNS N07725: Part I. Adapting the Double-Loop Electrochemical Potentiokinetic Reactivation Test

2021 ◽  
Vol 168 (3) ◽  
pp. 031506 ◽  
Author(s):  
Maria Sofia Hazarabedian ◽  
Michael Lison-Pick ◽  
Md Zakaria Quadir ◽  
Mariano Iannuzzi
Keyword(s):  
Double Loop ◽  
Electrochemical Potentiokinetic Reactivation

Effect of Sensitization Time on Intergranular Corrosion of 347H Stainless Steel

2021 ◽  
Vol 904 ◽  
pp. 506-511
Author(s):  
Liang Chang ◽  
Xue Tao Zhang ◽  
Zhi Juan Zhao ◽  
Yun Yan Peng ◽  
Jing Miao Li ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Stainless Steel ◽  
Intergranular Corrosion ◽  
Corrosion Test ◽  
Double Loop ◽  
Maximum Value ◽  
Microscopic Morphology ◽  
Epr Test ◽  
Sensitization Time

In this paper, 347H stainless steel of three situation of solution, primary and secondary stabilizing with 0, 12, 24, 48 and 72 h accelerated sensitization heat treatment. The change of sensitization degree with time was studied by metallographic test, double-loop electrochemical potentiodynamic reactivation (DL-EPR) test, intergranular corrosion test and microscopic morphology observation. The result shows that the sensitization degree of the solution material increases rapidly and reaches the maximum value after 12h sensitization heat treatment. After that, it still belonged to severe sensitization situation, but the index gradually decreased. After stabilizing heat treatment, the sensitization degree of the material is lower than the situation of solution. After heat treatment for 48h, the material located on “possible sensitization” range, and the sensitization degree of the secondary stabilized material was always lower than is of the primary. It indicates that the sensitization of materials can not be completely inhibited by stabilizing heat treatment, and other anti-corrosion measures should be considered.

PM-HIP Research for Pressure Retaining Applications Within the Electric Power Industry

2014 ◽  
Author(s):  
David Gandy ◽  
John Siefert ◽  
Lou Lherbier ◽  
David Novotnak
Keyword(s):  
Electric Power ◽  
Nuclear Power ◽  
Hot Isostatic Pressing ◽  
Electric Power Industry ◽  
Power Industry ◽  
Plate Rolling ◽  
Alloy 690 ◽  
Class 1 ◽  
Water Reactors ◽  
Grade 91

For more than 60 years now, the nuclear power industry has relied on structural and pressure retaining materials generated via established manufacturing practices such as casting, plate rolling-and-welding, forging, drawing, and/or extrusion. During the past three years, EPRI has been leading the development and introduction of another established process, powder metallurgy and hot isostatic pressing (PM/HIP), for pressure retaining applications in the electric power industry. The research includes assessment of two primary alloys: 316L stainless steel and Grade 91 creep-strength enhanced ferritic steels, for introduction into the ASME Boiler and Pressure Vessel Code. Continuing DOE and EPRI research on other structural/pressure retaining alloys such as Alloy 690, SA 508 Class 1, Alloy 625, hard-facing materials, and others are also underway. This research will have a tremendous impact as we move forward over the next few decades on the selection of new alloys and components for advanced light water reactors and small modular reactors. Furthermore, fabrication of high alloy materials/components may require the use of new manufacturing processes to achieve acceptable properties for higher temperature applications such as those in Generation IV applications. Current research by EPRI and DOE will be reviewed and emphasis will be targeted at advanced applications where PM/HIP may be applied in the future.

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