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Low cycle fatigue behaviors of SA508-3 low-alloy steel were investigated in room-temperature air, high-temperature air and in light water reactor (LWR) water environments. The fatigue mean curve and design curve for the low-alloy steel are developed based on the fatigue data in room-temperature and high-temperature air. The environmental fatigue model for low-alloy steel is developed by the environmental fatigue correction factor (Fen) methodology based on the fatigue data in LWR water environments with the consideration of effects of strain rate, temperature, and dissolved oxygen concentration on the fatigue life.

• Research highlights of the present work are listed as follows: • FeCrAl alloys exhibited better corrosion resistance than commercial Zircaloy-4. • Oxide film consists of outer Fe 3 O 4 layer, inner spinel layer and transition layer. • Compact spinel layer in inner layer can block inward diffusion of oxygen. • Porous spinel layer in inner layer was caused by outward diffusion of Fe2+. • The small addition of yttrium had no effect on corrosion of FeCrAl alloys. The uniform corrosion behavior of model FeCrAl alloys as well as commercial Zircaloy-4 as reference material were investigated in 360 °C borated and lithiated water. The results reveal that FeCrAl alloys exhibited better corrosion resistance than Zircaloy-4. It is found that the oxide films formed on the FeCrAl alloys are composed of outer Fe 3 O 4 layer, inner layer consisting of compact spinel layer and porous spinel layer, and transition layer containing Al-Cr-rich oxides and matrix enriched with Fe°. The spinel oxides in the inner layer are FeFe 2- x - y -z Cr x Al y Mo z O 4. The corrosion mechanism of FeCrAl alloys in high temperature water is discussed. [ABSTRACT FROM AUTHOR]

• TiN inclusions provided preferred sites for pitting corrosion. • S 2 O 3 2− inhibited corrosion of Alloy 690 in aerated chloride solution. • Reduction of S 2 O 3 2− to S0 and S2− enhanced corrosion in deaerated solution. • S 2 O 3 2− caused severe pitting corrosion inside the crevice in deaerated solution. The crevice corrosion behavior of Alloy 690 was investigated in high-temperature chloride solution containing different concentrations of thiosulfate (S 2 O 3 2−) and dissolved oxygen (DO). The S 2 O 3 2− inhibited corrosion of Alloy 690 through consuming oxygen in aerated chloride solution. In deaerated chloride solution, the S 2 O 3 2− was reduced to S° and S2− and subsequently incorporated into the oxide films, which promoted the pitting corrosion at locations of both TiN inclusions and matrix inside the crevice during the crevice corrosion as well as influenced the composition and thickness of the oxide films. The effect mechanisms of S 2 O 3 2− and DO on crevice corrosion in high-temperature chloride solution are discussed. [ABSTRACT FROM AUTHOR]

Effects of 405 stainless steel (405 SS) on crevice corrosion behavior of Alloy 690 in high-temperature pure water were investigated. Results revealed that the corrosion rate of Alloy 690 was low within the crevice. It was likely attributed to the fact that a Cr-rich inner oxide film and a Ni-rich layer beneath this oxide film formed upon Alloy 690, inhibiting the diffusion of oxygen towards the oxide/matrix interface. Moreover, the Fe2+ ions dissolved from 405 SS consumed most of oxygen, leading to less oxygen participating in the oxidation of Alloy 690. In addition, it was found that Fe concentration continuously decreased from the surface of the inner oxide film to the oxide/matrix interface of Alloy 690 within the crevice, which was probably due to the diffusion of Fe2+ ions dissolved from 405 SS into the inner oxide film. [ABSTRACT FROM AUTHOR]

Corrosion fatigue behavior of Alloy 52/52M dissimilar metal weld (DMW) was investigated in borated and lithiated high-temperature water. The fatigue life of Alloy 52/52M DMW in high-temperature water decreased in comparison with that in air. The fatigue cracks initiated at Alloy 52M butt weld or at the interface of Alloy 52 buttering and Alloy 52M butt weld. The welding residual strain and ductility dip cracking in Alloy 52M butt weld promoted the initiation and propagation of fatigue cracks. The environmentally assisted fatigue damage in high-temperature water is discussed by taking account of microstructure defects. [ABSTRACT FROM AUTHOR]

Uniform corrosion, pitting corrosion and passivation of 304 stainless steel were promoted and pattern recognition system (PRS) based on electrochemical noise (EN) measurements was employed to classify these corrosion mechanisms in laboratory-scale. The EN signals were analyzed using statistical, shot noise, wavelet and recurrence quantification analysis. It was found that the PRS designed by combining these EN parameters has a discriminant accuracy of 99.7%, which is superior to those designed by solely statistical parameters (92.4%), and the parameters selected by principle component analysis (97.8%). The application of the PRS above is evaluated by considering environmental factors and material types.

Fatigue strength of the structural materials of lead-cooled fast reactors (LFRs) and accelerator-driven systems (ADS) may be degraded in liquid metal (Lead or lead-bismuth eutectic (LBE)) environments. The fatigue crack growth (FCG) data of structural materials in liquid LBE are necessary for damage tolerance design, safety assessment and life management of key equipment. A novel monitoring system for fatigue crack length was designed on the compliance method and the monitor technology of crack opening displacement (COD) of CT specimens by the linear variable differential transformers (LVDT) system. It can be used to predict the crack length by monitoring the COD of CT specimens in harsh high-temperature liquid LBE using a LVDT system. The prediction accuracy of this system was verified by FCG experiments in room temperature air and liquid LBE at 150, 250 and 350 °C. The first results obtained in the FCG test for T91 steel in liquid LBE at 350 °C are presented.

Corrosion fatigue crack growth (FCG) behavior of 316LN stainless steel was investigated in high-temperature pressurized water at different temperatures, load ratios (R = Kmax/Kmin) and rise times (tR). The environmental assisted effect on FCG rate was observed when both the R and tRexceeded their critical values. The FCG rate showed a linear relation with stress intensity factor range (ΔK) in double logarithmic coordinate. The environmental assisted effect on FCG rate depended on the ΔKand quantitative relations were proposed. Possible mechanisms of environmental assisted FCG rate under different testing conditions are also discussed.

Uniform corrosion, pitting corrosion and passivation of 304 stainless steel were promoted and pattern recognition system (PRS) based on electrochemical noise (EN) measurements was employed to classify these corrosion mechanisms in laboratory-scale. The EN signals were analyzed using statistical, shot noise, wavelet and recurrence quantification analysis. It was found that the PRS designed by combining these EN parameters has a discriminant accuracy of 99.7%, which is superior to those designed by solely statistical parameters (92.4%), and the parameters selected by principle component analysis (97.8%). The application of the PRS above is evaluated by considering environmental factors and material types.