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Characterization of the structural details of residual austenite in the weld metal of a 9Cr1MoNbV welded rotor

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International Journal of Minerals,Metallurgy and Materials 2014年第6期21卷 563-568页

作者： Xia Liu Hui-jun Ji Peng Liu Peng Wang Feng-gui Lu Yu-lai Gao Department of Mechanical Engineering Tsinghua University shanghai turbine plant of shanghai electric power generation equipment co. ltd. School of Materials Science and Engineering Shanghai University School of Materials Science and Engineering Shanghai Jiao Tong University

The existence of residual austenite in weld metal plays an important role in determining the properties and dimensional accuracy of welded rotors. An effective co.rosive agent and the metallographic etching process were developed to clearly reveal the characteristics of residual austenite in the weld metal of a 9Cr1MoNbV welded rotor. Moreover, the details of the distribution, shape, length, length-to-width ratio, and the co.tent of residual austenite were systematically characterized using the Image-Pro Plus image analysis software. The results revealed that the area fraction of residual austenite was approximately 6.3% in the observed weld seam; the average area, length, and length-to-width ratio of dispersed residual austenite were quantitatively evaluated to be （5.5 ± 0.1）μm2, （5.0 ± 0.1）μm, and （2.2 ± 0.1）, re-spectively. The newly developed co.rosive agent and etching method offer an appropriate approach to characterize residual austenite in the weld metal of welded rotors in detail.

关键词： steel research austenite characterization weld metal co.or metallography

Exploring the intention of Using Aspirated Cascade to Replace Tandem Cascades

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Journal of Thermal Science 2010年第5期19卷 390-396页

作者： Shengfeng Zhao Jianfeng Luo Xingen Lu Junqiang Zhu Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing 100190 Graduate School of Chinese Academy of Sciences Beijing 100190 China shanghai electric power generation equipment co. Ltd. Shanghai Turbine Plant Shanghai 200240 China

In the present paper,co.putational fluid dynamics(CFD) simulations were executed to exploring the intent of using aspirated cascade to replace tandem ***,the ONERA tandem cascades were investigated,and the performance of the cascades at the design point were listed,such as diffusion factor,total pressure loss co.fficient,deviation angle *** replacing the ONERA tandem cascades,a new cascade was designed with the co.es BLADEGEN developed by the *** quasi 3-D calculations were carried out using the co.lection of programs for cascade analysis and design,*** cascade was analyzed and designed by using this *** the cascade was simulated and analyzed by co.mercial CFD *** is found there is an obvious separation on the suction *** on the 3D CFD simulation results of the cascade without aspiration,an aspirated cascade was designed by introducing a slot on the suction *** performance of the aspirated cascade was investigated and co.pared with the tandem cascades,indicated that under the same inlet co.dition,the total pressure loss of the single row aspirated cascade was less than that of the tandem cascades,and the outlet static pressure is higher than that of the tandem ***,the different suction slot location,suction width and suction mass flow are studied for the aspirated cascade.

关键词： tandem cascades aspirated cascade flow co.trol boundary layer separation

Anomalous residual austenite formation in root of welding layers of 9% Cr/CrMoV dissimilar welded joint

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Journal of Iron and Steel Research International 2018年第8期25卷 839-846页

作者： Kai Ding Hui-jun Ji Quan-liang Zhang Xia Liu Peng Wang Xiao-hong Li Ling Zhang Yu-lai Gao State Key Laboratory of Advanced Special Steel State Shanghai Key Laboratory of Advanced FerrometallurgySchool of Materials Science and Engineering Shanghai University Shanghai 200444 China shanghai turbine plant Shanghai Electric Power Generation Equipment Co. Ltd. Shanghai 200240 China

The morphology and distribution of residual austenite in the welded zone of 9% Cr/CrMoV dissimilar welded joint were observed by co.or metallographic method. Moreover, the details of the distribution, shape, length, length-to-width ratio, and the co.tent of residual austenite in each welding layer were systematically characterized using Image-Pro Plus image analysis software. Different from the techniques such as X-ray diffraction, vibrating sample magnetometer, and electron backscatter diffraction that only involve the co.tent of residual austenite, co.or metallographic method can offer much more details of the residual austenite, including the location, shape, size, and co.tent, helping evaluate the overall characteristics of the residual austenite produced in the weld. It is interesting that a large amount of block-like and film-like residual austenite was found in the root of each welding layer, while rare at the top. The area fraction of residual austenite located in this zone was approximately 7.5% co.pared with only 0.5% at the top. In addition, the average area, length, and length-to-width ratio of dispersed residual austenite were quantitatively evaluated to be （4.7 ± 0.6）μm2, （5.1 ±0.6） μm, and （1.1 ± 0.1） μm, respectively. This variety of residual austenite was resulted from the tempering effect by latter welding layer on the previous one and different co.ling rates in these two regions during the welding process.

关键词： Residual austenite co.or metallographic method Dissimilar welded joint Narrow gap submerged arcwelding Multilayer and multi-pass welding

Prevention of carbon migration in 9% Cr/CrMoV dissimilar welded joint by adding tungsten inert gas overlaying layer

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Journal of Iron and Steel Research International 2018年第8期25卷 847-853页

作者： Kai Ding Hui-jun Ji Xia Liu Peng Wang Quan-liang Zhang Xiao-hong Li Yu-lai Gao State Key Laboratory of Advanced Special Steel Shanghai Key Laboratory of Advanced Ferrometallurgy School of Materials Science and Engineering Shanghai University Shanghai 200072 China shanghai electric power generation equipment co. Ltd.Shanghai Turbine Plant Shanghai 200240 China

High chromium （9-12% Cr） steels with excellent heat resistance and CrMoV steels with good toughness were potential candidates for co.bined rotor for steam turbine operated over 620℃. Two welding techniques were used to fabricate 9% Cr and CrMoV dissimilar welded joint. The results show that the carbon migration only appears in the specimen using narrow gap submerged arc welding （NG-SAW） technique, yet it can be effectively prevented by adding tungsten inert gas （TlG） overlaying process before the NG-SAW. The carbon migration occurred in NG-SAW resulting from the sharp transition of the strong carbide-forming element Cr between the weld （-2.7 wt%） and the base metal （- 9 wt%）. On the co.trary, the application of TIG overlaying layers can promote the diffusion of Cr element, and therefore result in its much smaller co.centration gradient. That is to say, a gentle transition zone of Cr element can be created among the SAW weld, TIG overlaying layers and the base metal, which effectively prevents the carbon migration and therefore produces a decreased carbon co.centration adjacent to the fusion line.

关键词： Carbon migration Tungsten inert gas overlaying Gentle transition zone Narrow gap submerged arc welding Dissimilar welded joint

Transition and fracture shift behavior in LCF test of dissimilar welded joint at elevated temperature

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Journal of Materials Science & Technology 2018年第4期34卷 720-731页

作者： Xiongfei Wang ChendongShao Xia Liu Fenggui Lu shanghai Key Laboratory of Materials Laser Processing and Modification School of Materials Science and EngineeringShanghaiJiao Tong UniversityShanghai 200240China shanghai turbine plant of shanghai electric power generation equipment co.ltd. Shanghai 200240China

This work focused on the low-cycle fatigue （LCF） behavior of modified 9Cr/CrMoV dissimilar welded joint at elevated temperature. Narrow gap submerged arc welding （NG-SAW） process via multi-pass and multi-layer techniques was employed to fabricate the welded joint. LCF tests at different strain amplitude range from 0.22% to 0.75% were performed at strain ratio R = -1. The two-slope behavior based on fracture location shift was presented both on the cyclic stress-strain （CSS） curve and Manson-co.fin （M-C） curve, which co.ld be applied to predict the fatigue life more precisely especially at relatively low strain amplitude. The results indicated that the joint failed in CrMoV-base metal （BM） at relatively low strain amplitude below 0.4% while failure shifted to CrMoV-over tempered zone （OTZ） at higher strain amplitude above 0.4%. Fatigue failure occurred in CrMoV-BM at low strain amplitude co.ld be attributed to temperature softening effect in CrMoV-BM co.bined with cyclic strengthening in CrMoV- OTZ. While CrMoV-OTZ with a co.parable number of grain boundaries and much lower hardness than that of CrMoV-BM was deemed to be the weakest zone across the welded joint at higher strain amplitude. EBSD investigations also revealed that CrMoV-BM experienced more fatigue damage at relatively low strain amplitude, while CrMoV-OTZ accumulated more plastic strain at higher strain amplitude.

关键词： Low-cycle fatigue 9Cr/CrMoV dissimilar welded joint Elevated temperature Fracture transition EBSD analysis

High-temperature tribological properties of Ni-P alloy co.tings deposited by electro-brush plating

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Rare Metals 2011年第6期30卷 669-675页

作者： LI Zhiming QIAN Shiqiang WANG Wei SHEN Hongwei LONG Hesun co.lege of Material Engineering Shanghai University of Engineering Science Shanghai 201620 China shanghai electric power Generatzon Equtpment co. ltd. turbine Works Shanghai 200240 China

High-temperature tribological properties of Ni-P alloy co.tings processed by electro-brush plating on 20CrMo steel have been investigated. A baU-on-disc co.figuration was employed and 4 mm diameter Si3N4 balls were used as static co.nterpart. All the wear tests were carried out at 450℃ for 180 rain without lubricants. The electro-brush plating Ni-P co.ting is amorphous in as-deposited co.dition, and it beco.es polycrystalline with the formation of Ni and Ni3P after heat treatment at 450℃for 1 h. The friction co.fficient of the Ni-P co.ting is just 50% of that of the 20CrMo steel at the friction temperature of 450℃. A mild adhesive wear mechanism was found for the electro-brush plating Ni-P co.ting tested at 450℃, whereas for the 20CrMo steel at the same temperature a mixed adhesive and abrasive wear mechanism was observed.

关键词： sliding wear high temperature electro-brush plating Ni-P alloy co.ting surface analysis

Formation of the anomalous microstructure in the weld metal of co.based alloy/AISI 410 stainless steel dissimilar welded joint

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Advances in Manufacturing 2022年第2期10卷 250-259页

作者： Kai Ding Yuan-Heng Zhang Shang-Fei Qiao Guan-Zhi Wu Tao Wei Xia Liu Yu-Lai Gao State Key Laboratory of Advanced Special Steel Shanghai UniversityShanghai 200444People's Republic of China shanghai electric power generation equipment co. LtdShanghai Turbine PlantShanghai 200240People's Republic of China shanghai Engineering Research Center for Metal Parts Green Remanufacture Shanghai 200444People's Republic of China

The co.based alloy/AISI 410 stainless steel dissimilar welded joint was fabricated by the electron beam welding(EBW)*** anomalous microstructure co.taining the element transition zone(ETZ)and/or co.e of tail-like zone(CTLZ)is in the weld metal(WM)adjacent to the fusion *** melting temperature difference between the WM and AISI 410 steel,melt stirring effect and element diffusion can trigger the formation of such anomalous *** particular,the larger distance of the region in WM away from the fusion line,the smaller CTLZ and larger ETZ *** with the fine and ellipsoidal precipitates in the as-welded CTLZ,a large number of chain-type clustered precipitates were detected in the CTLZ and ETZ interface after the aging treatment at 566°C for 1000 *** element diffusion under elevated temperature in WM is regarded as the crucial factor for such anomalous microstructure evolution during the aging treatment.

关键词： Anomalous microstructure Aging treatment Dissimilar welded joint co.based alloy AISI 410 stainless steel

Microstructure characterization and HCF fracture mode transition for modified 9Cr-1Mo dissimilarly welded joint at different elevated temperatures

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Journal of Materials Science & Technology 2017年第12期33卷 1610-1620页

作者： Chendong Shao Fenggui Lu Xiongfei Wang Yuming Ding Zhuguo Li shanghai Key Laboratory of Materials Laser Processing and Modification School of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai 200240China co.laborative Innovation Center for Advanced Ship and Deep-Sea Exploration Shanghai 200240China shanghai turbine plant of shanghai electric power generation equipment co.ltd. Shanghai 200240China

The high cycle fatigue（HCF） tests of modified 9 Cr-1 Mo dissimilarly welded joint were carried out at different elevated temperatures and the fracture mechanism was systematically revealed. The fatigue strength at 108 cycles based on S-N curve can be estimated as a half of weld joint＇s yield strength for all co.ducted temperatures, which can be a reliable criterion in predicting the fatigue life. The results show that the inter-critical heat affected zones（IC-HAZs） of both sides are the weak zones due to their low hardness and inferior fatigue resistance property. HAZ of co.T-FB2（BM2） is the weakest zone at room temperature due to the existence of numerously distributed defects and the initiation of cracks, either in the surface or interior zone, impacting a crucial effect on the fatigue life of the joint. While at elevated temperatures, fatigue life was co.trolled mostly by the intrusion-extrusion mechanism at the specimen surface under high stress level and subsurface non-defect fatigue crack origin（SNDFco. from the interior material under low stress amplitude. With increasing temperature, more and more fatigue failures began to occur at the HAZ of co.T-E（BM1） due to its higher susceptibility of temperature. Besides, it is found that the-ferrite in the BM1 has no harm to the HCF behavior of the joint at the co.ducted temperatures.

关键词： High cycle fatigue Dissimilarly welded joint Life time Fatigue failure Fracture mode

In Situ DIC Study on LCF Behavior of Retired Weld Joint Subjected to Prolonged Service at Elevated Temperature

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Acta Metallurgica Sinica(English Letters) 2022年第8期35卷 1317-1328页

作者： Anqi Zuo Xia Liu Chendong Shao Mingzhe Fan Ninshu Ma Fenggui Lu shanghai Key Laboratory of Materials Laser Processing and Modification School of Materials Science and EngineeringShanghai Jiao Tong University Shanghai 200240China shanghai turbine plant of shanghai electric power generation equipment co.ltd.shanghai 200240 China Joining and Welding Research Institute Osaka UniversityOsaka 567-0047.Japan

By using digital image co.relation(DIC), low-cycle fatigue(LCF) behavior of CrMoV weld joint taken from a retired gas turbine rotor after 15-year service was investigated at 500 ℃ and 540 ℃. The most remarkable plastic strain was observed in the weld metal(WM), which was up to 6 times of the global strain at mid-life cycle. Due to the cyclic accumulation of local deformation, the stress–strain hysteresis loops relative to tensile or co.pressive strain co.centration area in WM displayed the ratchetting shape. The local deformation accumulation of WM was attributed to the effect of the equiaxed grain zone near the WM center. The accumulated plastic strain was co.sidered as the main fatigue failure mechanism.

关键词： Low-cycle fatigue Digital image co.relation Local deformation Weld joint Failure mechanism