To evaluate the rate of thermal embrittlement of type 316 low-carbon stainless steel weld metal at BWR operating temperature, aging test at 310°C, 335°C, and 400°C was carried out. Hardness of each ferrite and austenite phase of s pecimens was measured selectively by microhardness tester. Hardness of ferrite was increased apparently with all three aging temperatures, whereas hardness of austenite was not changed. Changes in the microstructure of ferrite ag ed at 310°C for 11,000h and 18,000h were analyzed ...
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Evaluation of aging embrittlement of low-carbon austenitic stainless steelweld metal near the BWR operating temperature

The purpose of this study is to investigate the following items focused on the microstructure near the fusion boundary of dissimilar weld joint with Ni-based weld metal and low alloy steel; (1) Microstructural characteristics near the fusion boundary, (2) Dominant factor that makes crack retardation near the fusion boundary. Main conclusions can be summarized as follows; (1) From the results of CBB tests, it has been understood that the low alloy s teel has no SCC susceptibility and that there is a differ...
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SCC propagation and cessation behavior near the fusion boundary of dissimilar weld jointwith Ni-based weld metal and low alloy steel

SCC behavior near the fusion boundary of dissimilar weld joint with Ni-based weld metal and low alloy steel in high temperature water has been investigated with special attention on relation t o the characteristics of microstructure. From the results of CBB test (1.0 ppm-Na2SO4 and 8 ppm dissolved oxygen), it has been obvious that the LAS has no SCC susceptibility. On the other hand, Alloy182 in the weld samples have SCC susceptibility. Most of crack tips have located at the fusion boundary, and the penetr...
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Characteristics of microstructure and SCC behavior near the fusion boundaryof Ni-base weld metal and low alloy steel

Austenitic stainless steels are widely used as structural materials in many industries. However, stainless steels are susceptible to crevice corrosion in the solution including chloride ions. In this paper, at first, the most inhibitive anion against corrosion was investigated by anodic polarization measurement of type 316L stainless steel in the solution containing Cl- with candidate inhibitive anions (WO42-, MoO42-, VO3-). MoO42- was adopted as the most inhibitive anion in this study. Next, the effec...
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Effect on critical potentials for crevice corrosion initiation and repassivation of stainless steel by addition of inhibitive anion

To ensure integrity of structures and components in nuclear power plants, the demand has been increased for establishing nondestructive method for detection of pre-existing plastic strain. In this study, potentiostatic etching method is applied to detect and quantitatively measure plastic strain imposed to austenitic stainless steels by tensile straining. After potentiostatic etching (1N HNO3, -600mVSCE, 20min), twin lines and slip lines appear as etched lines on the surface of specimen because of the...
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Inspection of Plastic Deformation Mechanism in Austenitic Stainless Steel by potentiostatic etching Detection Method

To ensure integrity of structures and components in nuclear power plants, the demand has been increased for establishing nondestructive method for detection of pre-existing plastic strain. In this study, potentiostatic etch ing method is applied to detect and quantitatively measure plastic strain imposed to austenitic stainless steels by tensile straining. After potentiostatic etching (1N HNO3, -600mVsce, 20min), twin lines and slip lines appe ar as etched lines on the surface of specimen because of the pr...
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Inspection of Temperature / Steel Composition Dependency of Plastic Deformation Mechanismin Austenitic Stainless Steel by potentiostatic etching Detection Method.

To ensure integrity of the structure such as nuclear power plant, the demand has been increased for establishing nondestructive method for detection of pre-existing plastic st rain. In this study, potentiostatic etching method is applied to detect and measure plastic strain imposed to austenitic stainless steel by tensile straining. After potensiost atic etching (1N HNO3, -600mVsce, 20min), the twin band appears as etched line on the surface of specimens. The etched twin band is observed by optical microsc...
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Potentiostatic Etching Method for Detection of Pre-existing Plastic Strainin Austenitic Stainless Steel

SCC behavior near the fusion line of 316L SS welds in high SCC behavior near the fusion line of 316L SS welds in high temperature water has been investigated with special attention on relation to the characteristics of microstructure. Island-type S-ferrite has been distributed on grain boundary, namely along the potential crack path, in partially melted zone of 316L SS weld samples. Most of crack tips have been located on d-ferrite in partially melted zone of both weld samples. Cr2O3 which makes low oxida...
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SCC Retardation Mechanism near Fusion Boundary in 316L SS Welds from Microstructure Point of View

Oxidation behavior and cracking susceptibility of the Ni-Cr alloys (Ni-14Cr, Ni-22Cr and Ni-30Cr) under extremely-low oxygen partial pressure have been investigated by experiments used as plate specimen and Reverse U-Bend (RUB) specimen for 750 hours at 400 °C in two kinds of gas system (inert gas and dry steam) under various oxygen potential (Ni stable, Ni/NiO equilibrium and NiO stable).The Ni-Cr alloys cracked along grain boundary both in inert gas system (with trace O2, without H2O ) and in hydrogenat...
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Oxidation behavior under stress of Ni-Cr alloys in gas phase under extremely-low oxygen potential

内一 哲哉 Tetsuya UCHIMOTO Although electrochemical transients can provide very sensitive indication about the onset of localized corrosion, including initiation of stress corrosion cracking (SCC), information on location of the initiation site is not available. In the present study, we proposed an estimation method of location and m agnitude of SCC initiation events, where electrochemical transients associated with local anodic events are measured by multiple reference electrodes and location of the initi...
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Electrochemical Method for Monitoring Film Ruptures in SCC Initiation Processes