Fretting wear behavior of Zr alloy cladding tube mated with Zr alloy dimple under mixed fretting regime in simulated primary water of PWR

The fretting wear behavior of Zr alloy cladding tube under mixed fretting regime in a high-temperature pressurized water was investigated.The main wear mechanism is adhesive wear,with characters of small-scale delamination at the center of worn area and serious delamination on the worn edge.A long crack throughout the worn area and other cracks propagated towards the substrate are observed.The cross-sectional microstructure of worn area can be divided into a thick third-body layer,thin inner oxide layer and thick tribologically transformed structure layer,and their formation mechanisms are analyzed in detail.Finally,the mixed fretting regime process and the microstructural evolution during fretting wear are discussed.

Effect of Normal Force on Fretting Wear Behavior of Zirconium Alloy Tube in Simulated Primary Water of PWR

The effect of normal force on fretting wear behavior of zirconium alloy tube mated with grid dimple in simulated primary water of pressurized water reactor nuclear power plant was investigated.Results showed that the maximum wear depth,wear volume and wear coefficient of Zr alloy tube in simulated primary water at 315℃ gradually increased with increasing normal force,while the friction coefficient gradually decreased.Fretting process could be divided into four stages according to the variation of friction coefficient during test.When normal force exceeds 30 N,the fretting regime would transition from gross slip regime to partial slip regime after 3×10^(7 )cycles.Delamination was aggravated with increasing normal force,while abrasive wear became slighter.A thicker third-body layer with monoclinic ZrO_(2) was formed by the tribo-sintering mechanism under higher normal force.In addition,the schematic evolution processes of delamination and third-body layer formation were displayed according to morphology observation.

A new method to determine the synergistic effects of area ratio and microstructure on the galvanic corrosion of LAS A508/309 L/308 L SS dissimilar metals weld

The synergistic effects of area ratio and microstructure on the galvanic corrosion of A508/309 L/308 L dissimilar metals weld(DMW)are studied by a multi-analytical approach.It was demonstrated that decreasing the anode/cathode surface area ratio obviously enhances the corrosion rate of A508,both locally and globally.Deeper analyses of the AFM results enabled quantitative comparison of the corrosion behaviour of the different surface constituents.It was revealed that in the galvanic interaction of the DMW,the grain refined region corrodes most,followed by the partial grain refined region and base metal matrix of the A508,respectively.The electrochemical localization index(LI)estimation method and AFM analysis both confirmed the presence of a mixed(localized and uniform)corrosion phenomenon occurring on the surface of the A508 anode metal in the galvanic interaction of the dissimilar metals.Finally,the degree of synergism equation was utilized to describe the synergistic effects of anode/cathode area ratio and the microstructure of the samples on the galvanic corrosion of LAS A508/309 L/308 L SS DMW.

Effects of surface grinding for scratched alloy 690TT tube in PWR nuclear power plant:Microstructure and stress corrosion cracking

Alloy 690TT tube samples with different scratch depths were repaired by grinding treatments using abra-sive papers of two different particle sizes.The microstructure and stress corrosion cracking(SCC)behavior were studied in detail.During grinding,the plastic accumulation zone vulnerable to SCC was removed.Meanwhile,some residual slip steps remained in the scratched area.Corrosion tests lasting 1000,2000,3000,and 4000 h show that the sensitivity and risk of SCC in the scratched area are decreased by grind-ing.Treatment using abrasive particles of a smaller size is more effective.Nevertheless,deep scratches remained hazardous even after the grinding.

Multilayer Graphene:A Potential Anti-oxidation Barrier in Simulated Primary Water

Multilayer graphene as a potential anti-oxidation barrier to protect nickel foils from oxidation was studied in simulated primary water of pressurized water reactors （PWRs）. The results show that after immersion for 1000 h, the structure of the multilayer graphene remains unchanged and no obvious oxide film formed on the graphene coated nickel foils, indicating multilayer graphene can effectively act as the anti-oxidation barrier to protect the substrate from oxidation and hence can improve the heat transfer efficiency of the substrate in simulated primary water of PWRs.

Effect of temperature on corrosion behavior of alloy 690 in high temperature hydrogenated water

The influence of temperature on the corrosion behavior of Alloy 690 is evaluated using potentiodynamic polarization curves, electrochemical impedance spectra （EIS）, scanning electron microscopy （SEM）, X- ray photoelectron spectroscopy （XPS） and transmission electron microscopy （TEM）. The corrosion rate of Alloy 690 reaches a local maximum at 250℃. The kinetic control step of the growth of oxide film changes from the diffusion process of aqueous-phase ions to the growth of Cr-rich barrier layer in the temperature range of 200-300 ℃. A modified double-layer model is proposed to describe the effect of temperature on the structure and composition of the oxide film.

Transferred Monolayer Graphene as a Potential Anti-Oxidation Barrier for Alloy 690TT in Simulated Primary Water

To explore the usage of monolayer graphene as an anti-oxidation barrier in simulated primary water of pressurized water reactors（PWRs）,we transferred the monolayer graphene synthesized by low pressure chemical vapor deposition（LPCVD） on Cu foil to Alloy 690 TT.After a 500 h immersion,strong oxidation resistance was obtained from the graphene coated Alloy 690 TT sample,indicating that the transferred monolayer graphene can act as an effective barrier to protect the substrate from oxidation in simulated primary water of PWRs.