Reducing Potential for Stress Corrosion Cracking During Design and Fabrication of Small Modular Reactors

2011 ◽  
Author(s):  
Lloyd A. Hackel ◽  
C. Brent Dane ◽  
Jon Rankin ◽  
Fritz Harris ◽  
Chanh Truong
Keyword(s):  
Residual Stress ◽  
Tensile Stress ◽  
Laser Beam ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Compressive Residual Stress ◽  
Cost Effective ◽  
Corrosion Cracking ◽  
Laser Peening ◽  
Corrosive Environment

Reactor designs employ the best materials available such as Alloy 600 and Alloy 690 to resist stress corrosion cracking (SCC); yet the problem has continued to exist. As SCC is driven by three main contributors, susceptible material, corrosive environment and existence of tensile stress, eliminating any one can greatly improve the situation. In this paper we discuss a laser peening process for the nuclear industry that can convert areas of tensile stress to deep levels of compression. Laser peening induces deep levels of plasticity into materials resulting in compressive residual stress to depths of 0.100 inches (2.5 mm) or deeper. This enables increased fatigue strength and lifetimes and greatly enhances resistance to stress corrosion cracking. The deep plasticity closes the inter-granular boundaries and induces a deep layer of compressive stress dramatically improving the stress corrosion cracking (SCC) resistance of components subjected to tensile loading in a corrosive environment. The deeper plasticity generated by laser peening can be contrasted to a depth of only 0.010 inches (0.25 mm) typically achieved with conventional shot peening, a beneficial and widely used technology. Advances in laser technology have enabled highly reliable, high-rate, cost-effective processing that has made a major impact in aerospace; thousands of parts and large scale structures have been and are being treated. Advanced laser beam delivery to components has enabled cost-effective field applications. The peening is done without physical contact with the component. The technology has been approved by organizations such as the FAA, EASA and USAF and deployed to enhance lifetime of key structural components on the F-22 fighter. Component faducials on a structure are first visually detected by a camera and alignment laser and then the main laser beam is automatically aligned to the component. The technology has the potential to serve a broad range of fielded industrial applications including oil and gas lines, on-board ship applications, nuclear power plants, upstream exploration and recovery, and downstream oil refining. We will discuss examples of advanced fatigue and corrosion resistance in steels provided by the laser peening technology as well as the hardware now available for field use. The laser peening technology enables SCC mitigation via engineered compressive residual stress to be considered much more seriously at the design level for reactors.

Laser Peening without Coating to Mitigate Stress Corrosion Cracking and Fatigue Failure of Welded Components

2008 ◽  
Vol 580-582 ◽  
pp. 519-522 ◽  
Author(s):  
Yuji Sano ◽  
Yoshihiro Sakino ◽  
Naruhiko Mukai ◽  
Minoru Obata ◽  
Itaru Chida ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Compressive Residual Stress ◽  
Fatigue Testing ◽  
Corrosion Cracking ◽  
Laser Peening ◽  
Alloy 600 ◽  
Metallic Materials ◽  
Laser Peening Without Coating

The authors have applied laser peening without coating (LPwC) to metallic materials. Compressive residual stress nearly equal to the yield strength of the materials was imparted on the surface. Accelerating stress corrosion cracking (SCC) tests showed that LPwC had a significant effect to prevent the SCC initiation of sensitized materials of SUS304, Alloy 600 and the weld metal, Alloy 182. Push-pull type fatigue testing demonstrated that LPwC drastically enhanced the fatigue strength of fillet-welded rib-plates of SM490A.

scholarly journals Assessment of Tensile Residual Stress Mitigation in Alloy 22 Welds Due to Laser Peening

2004 ◽  
Vol 126 (4) ◽  
pp. 465-473 ◽  
Author(s):  
Adrian T. DeWald ◽  
Jon E. Rankin ◽  
Michael R. Hill ◽  
Matthew J. Lee ◽  
Hao-Lin Chen
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Compressive Residual Stress ◽  
Base Material ◽  
Corrosion Cracking ◽  
Contour Method ◽  
Laser Peening ◽  
Alloy 22

This paper examines the effects of laser peening on Alloy 22 (UNS N06022), which is the proposed material for use as the outer layer on the spent-fuel nuclear waste canisters to be stored at Yucca Mountain. Stress corrosion cracking (SCC) is a primary concern in the design of these canisters because tensile residual stresses will be left behind by the closure weld. Alloy 22 is a nickel-based material that is particularly resistant to corrosion; however, there is a chance that stress corrosion cracking could develop given the right environmental conditions. Laser peening is an emerging surface treatment technology that has been identified as an effective tool for mitigating tensile redisual stresses in the storage canisters. The results of laser-peening experiments on Alloy 22 base material and a sample 33 mm thick double-V groove butt-weld made with gas tungsten arc welding (GTAW) are presented. Residual stress profiles were measured in Alloy 22 base material using the slitting method (also known as the crack-compliance method), and a full 2D map of longitudinal residual stress was measured in the sample welds using the contour method. Laser peening was found to produce compressive residual stress to a depth of 3.8 mm in 20 mm thick base material coupons. The depth of compressive residual stress was found to have a significant dependence on the number of peening layers and a slight dependence on the level of irradiance. Additionally, laser peening produced compressive residual stresses to a depth of 4.3 mm in the 33 mm thick weld at the center of the weld bead where high levels of tensile stress were initially present.

A Development of the Technical Basis for the New Code Case “Mitigation of PWSCC and CISCC in ASME Section III Components by the Advanced Surface Stress Improvement Technology”

2019 ◽  
Author(s):  
S. W. Cho ◽  
W. G. Yi ◽  
N. Mohr ◽  
A. Amanov ◽  
C. Stover ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Surface Stress ◽  
Compressive Residual Stress ◽  
Corrosion Cracking ◽  
Chloride Salt ◽  
Spent Fuel ◽  
Term Operation ◽  
Technical Basis

Abstract It is necessary for nuclear power plant operation and spent fuel canisters to provide a sound technical basis for the safety and security of long-term operation and storage respectively. A new code case for mitigation of Primary Water Stress Corrosion Cracking (PWSCC) and Chloride Induced Stress Corrosion Cracking (CISCC) in Section III components by using an advanced surface stress improvement technology (ASSIT) is being developed by Task Group ASSIT which is one of the task groups under the ASME (The American Society of Mechanical Engineers). The necessary technical reports supporting this code case are being developed as part of joint research projects conducted by Doosan Heavy Industries and Construction (DOOSAN), Electric Power Research Institute (EPRI) and Sun Moon University (SMU). A well-known approach to prevent PWSCC and CISCC are to be performed using materials resistant to PWSCC and CISCC. The objective is to eliminate residual tensile stresses, or to induce compressive residual stress using ASSIT methods such as laser peening, water jet/cavitation peening, ultrasonic peening and ultrasonic nanocrystal surface modification (UNSM). Performance and measurement criteria for mitigation of PWSCC by ASSIT will be established based on the magnitude of surface stress and depth of compressive residual stress, sustainability, inspectability and lack of adverse effects. Additionally, for mitigation of CISCC by ASSIT, the evaluation of chloride induced corrosion pitting, the depth and density of corrosion pits and stress corrosion crack initiation and growth under chloride salt chemistry conditions are also being examined. This paper explains the approach, and progress of testing and analysis. The results and details from testing and analysis will be presented in a future PVP paper upon completion.

NRC/EPRI Residual Stress Validation Program Phase I: Experimental Specimen Modeling and Measurement

2011 ◽  
Author(s):  
J. Broussard ◽  
P. Crooker
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Phase 1 ◽  
Measurement Techniques ◽  
Corrosion Cracking ◽  
Welding Residual Stress ◽  
Hole Drilling ◽  
Pressurized Water

The US Nuclear Regulatory Commission (NRC) and the Electric Power Research Institute (EPRI) are working cooperatively under a memorandum of understanding to validate welding residual stress predictions in pressurized water reactor primary cooling loop components containing dissimilar metal welds. These stresses are of interest as DM welds in pressurized water reactors are susceptible to primary water stress corrosion cracking (PWSCC) and tensile weld residual stresses are one of the primary drivers of this stress corrosion cracking mechanism. The NRC/EPRI weld residual stress (WRS) program currently consists of four phases, with each phase increasing in complexity from lab size specimens to component mock-ups and ex-plant material. This paper describes the Phase 1 program, which comprised an initial period of learning and research for both FEA methods and measurement techniques using simple welded specimens. The Phase 1 specimens include a number of plate and cylinder geometries, each designed to provide a controlled configuration for maximum repeatability of measurements and modeling. A spectrum of surface and through-wall residual stress measurement techniques have been explored using the Phase 1 specimens, including incremental hole drilling, ring-core, and x-ray diffraction for surface stresses and neutron diffraction, deep-hole drilling, and contour method for through-wall stresses. The measured residual stresses are compared to the predicted stress results from a number of researchers employing a variety of modeling techniques. Comparisons between the various measurement techniques and among the modeling results have allowed for greater insight into the impact of various parameters on predicted versus measured residual stress. This paper will also discuss the technical challenges and lessons learned as part of the DM weld materials residual stress measurements.

Effects of Cold Working and Heat Treatment on Caustic Stress Corrosion Cracking of Alloy 800M

2005 ◽  
Vol 297-300 ◽  
pp. 993-998 ◽  
Author(s):  
Chun Bo Huang ◽  
Guang Fu Li ◽  
Zhan Peng Lu ◽  
Jian Min Zeng ◽  
Wu Yang
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Cold Working ◽  
Corrosion Cracking ◽  
Caustic Solution ◽  
Surface Films ◽  
Microstructure Examination ◽  
Increasing Temperature

The effects of cold working and heat treatment on caustic stress corrosion cracking (SCC) of mill annealed (MA) alloy 800M in boiling solution of 50%NaOH+0.3%SiO2+0.3%Na2S2O3 were investigated by means of microstructure examination, tensile test, X-ray stress analysis, SCC testing of C-rings, Auger electron spectroscopy (AES), scanning electron microscopy (SEM) and metallography. The microstructure of alloy 800M under tested conditions was austenite. With a train of 25% by cold working, the grains of alloy 800M became longer, yield strength (YS) and ultimate tensile strength (UTS) increased, elongation (δ ) decreased, residual stress and the susceptibility to SCC increased. With increasing temperature of heat treatment of alloy 800M with cold working, the grains became bigger , residual stress, YS and UTS decreased and δ increased, the susceptibility to SCC of alloy 800M decreased. In boiling caustic solution, SCC cracks on the surfaces of C-ring specimens polarized potentiostatically at –20mV/SCE initiated from pitting and propagated along grain boundaries. AES analysis indicated that the surface films on MA alloy 800M were enriched in nickel and depleted in iron and chromium.

scholarly journals Corrosion of High-Strength Steel Wires under Tensile Stress

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4790
Author(s):  
Shanglin Lv ◽  
Kefei Li ◽  
Jie Chen ◽  
Xiaobin Li
Keyword(s):  
Tensile Stress ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Immersion Time ◽  
High Strength ◽  
Corrosion Cracking ◽  
Corrosion Products ◽  
Corrosive Solution ◽  
Steel Wires ◽  
The Impact

The stress corrosion cracking is the central issue for high-strength wires under high tensile stress used in civil engineering. This paper explores the resistance of stress corrosion cracking of three typical steel wires of high-strength carbon through a laboratory test, combining the actions of tensile stress and corrosive solution. Besides, the impact of tensile stress and immersion time are also investigated. During the tests, the wires were subject to electrochemical measurements of potentiodynamic polarization and electrochemical impedance spectroscopy, and the microstructure analysis was performed on the fractured cross sections. The obtained results show the following: the high-strength wire, conforming to GB/T 5224, has higher resistance to the combined actions of tensile stress and corrosive solution; tensile stress of 70% fracture strength and longer loading-immersion time make the film of corrosion products on steel surface unstable and weaken the corrosion resistance; the surface film consisted of the iron oxide film and the corrosion products film whose components are mainly iron thiocyanate and iron sulphide.

Effect of Ultrasonic Impact Treatment on the Stress Corrosion Cracking of 304 Stainless Steel Welded Joints

2008 ◽  
Author(s):  
Gang Ma ◽  
Xiang Ling
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stainless Steel ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Welded Joints ◽  
Corrosion Cracking ◽  
Coarse Grained ◽  
304 Stainless Steel ◽  
Ultrasonic Impact Treatment

High tensile weld residual stress is an important factor contributing to stress corrosion cracking (SCC). Ultrasonic impact treatment (UIT) can produce compressive stresses on the surface of welded joints that negate the tensile stresses to enhance the SCC resistance of welded joints. In the present work, X-ray diffraction method was used to obtain the distribution of residual stress induced by UIT. The results showed that UIT could cause a large compressive residual stress up to 325.9MPa on the surface of the material. A 3D finite element model was established to simulate the UIT process by using a finite element software ABAQUS. The residual stress distribution of the AISI 304 stainless steel induced by UIT was predicted by finite element analysis. In order to demonstrate the improvement of the SCC resistance of the welded joints, the specimens were immersed in boiling 42% magnesium chloride solution during SCC testing, and untreated specimen cracked after immersion for 23 hours. In contrast, treated specimens with different coverage were tested for 1000 hours without visible stress corrosion cracks. The microstructure observation results revealed that a hardened layer was formed on the surface and the initial coarse-grained structure in the surface was refined into ultrafine grains. The above results indicate that UIT is an effective approach for protecting weldments against SCC.

X-Ray Fractography of Stress Corrosion Cracking in Aisi 4340 Steel Under Controlled Electrode potential

1987 ◽  
Vol 31 ◽  
pp. 269-276 ◽  
Author(s):  
Masaaki Tsuda ◽  
Yukio Hirose ◽  
Zenjiro Yajima ◽  
Keisuke Tanaka
Keyword(s):  
Residual Stress ◽  
Fracture Surface ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Electrode Potential ◽  
Diffraction Method ◽  
Corrosion Cracking ◽  
Fracture Mechanisms ◽  
X Ray ◽  
Electrode Potentials

The residual stress left on the fracture surface is one of the important parameters in X-ray fractography and has been used to analyze fracture mechanisms in fracture toughness and fatigue tests especially of high strength steels.In the present paper, the distribution of residual stress beneath the fracture surface made by stress corrosion cracking was measured by the X-ray diffraction method. Stress corrosion cracking tests were conducted by using compact tension specimens of 200°C tempered AISI steel in 3.5% NaCl solution environment under various electrode potentials. The effect of electrode potential on the growth kinetics of stress corrosion cracking is discussed on the basis of residual stress distribution.

Failure Analysis of a Cracked Outlet Elbow in Coal Gasification Unit

2015 ◽  
Author(s):  
Wen Liu ◽  
Shanshan Shao ◽  
QiuPing Chen ◽  
Jin Shi ◽  
ZhiRong Yang ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Coal Gasification ◽  
Stress Measurement ◽  
Corrosion Cracking ◽  
Chemical Components ◽  
Intergranular Stress Corrosion ◽  
Secondary Cracks ◽  
Strain Induced Martensite

A crack was observed on an outlet elbow of the pre-converter in coal gasification unit during operation. This paper details the investigation into the failure and highlights the most probable cause of failure based on available documents and experimental analysis. Visual examination, chemical components analysis, energy spectrum analysis, fracture analysis, metallurgical analysis, mechanical properties test and residual stress measurement were performed. The experimental results show that the primary crack initiated from inside and propagated to outer surface of the elbow. The content of titanium element was lower than the requirement in GB/T 14976-2002. Corrosion products were rich in O and S elements. Amounts of secondary cracks and strain induced martensite were observed. Furthermore, the residual stress on the inner surface near the crack tip was extremely high. According to the experiment results and the analysis of operating condition and history, the failure mechanism of the elbow is stress corrosion cracking. Sensitization of the stainless steel due to low Ti content and the faulty heat treatment contributed to the intergranular stress corrosion cracking.

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