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An C.,Shanghai Electrical Power Generation Equipment Co. | Liang L.,Pan Asia Technical Automotive Center Co.
Jinshu Rechuli/Heat Treatment of Metals | Year: 2015

A comprehensive microstructure evolution of 1Cr12Mo steel high-press steam turbine blade under the condition of long-term service was investigated, especially focusing on the influence of temperature and pressure on microstructure of the steel. The microstructure of the blades was analyzed by means of X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM). The results indicate that appropriate stress can promote the precipitation of carbide particles along the boundaries of lathes and the inside of the lathes. These very fine precipitated particles can retard the formation of dislocation tangles and dislocation cells. It is considered that the density of dislocation is reduced dramatically due to the formation of the dislocation cells. The temperature has a negligible impact on the formation and evolution of martensite and dislocation cells, while has a significant effect on the increasing the growth velocity of carbides. ©, 2015, Chinese Mechanical Engineering Society of Heat Treatment. All right reserved.

Xu Y.,Shanghai University | Liu Q.,Shanghai University | Wang F.,Shanghai University | Li J.,Shanghai University | And 3 more authors.
Materials and Design | Year: 2015

Long term stress-rupture life at 600°C/450MPa of Nimonic 80A with various duplex grain size distributions has been investigated. Stress-rupture life of duplex grain size samples significantly increases from about 4512h in the bimodal condition to 6863h in the banding condition and to 10,765h in the wide-range condition. Plate-like Cr23C6 prefers to precipitate at transition region of small dynamic recrystallization (DRX) grains and large original grains in the bimodal condition, which can easily lead to grain boundary (GB) cracking. Cracking is also found at small equiaxed recrystallized GB where is enriched with strip-like Cr23C6 in sample with abnormal grains in the banding condition. Blocky Cr23C6 exhibits an orientation relationship with γ at GB in sample in the wide-range condition. Blocky TiC with average size about 7.5μm precipitates at GBs firstly and then also in the grain interior, while the fine TiC with size about 300nm is found in grain interior and the morphology changes from lageniform or oval shape to spherical one with prolonged stress-rupture life. The γ' which maintains a coherent orientation relationship with γ is very stable. The duplex grain size distribution in the wide-range condition significantly improves stress-rupture life. © 2014 Elsevier Ltd.

Yu R.,Shanghai JiaoTong University | Zhou D.,Shanghai Electrical Power Generation Equipment Co. | Zhu X.,Shanghai JiaoTong University | Du Z.,Shanghai JiaoTong University
Dongli Gongcheng Xuebao/Journal of Chinese Society of Power Engineering | Year: 2014

An aerodynamic optimization design for turbine airfoil was developed using adaptive Kriging surrogate model, during which the airfoil geometry parameterization was realized with Bezier function and CFD method. Searching process of the surrogate model was improved, and the airfoil geometry was modified through controlling via Bezier control points, so as to automatically achieve optimization design of the leading edge of turbine blade. Results show that that higher pressure recovery coefficient and better aerodynamic performance are obtained after aerodynamic optimization of the airfoil, which proves the optimization model to be reliable and effective.

Lu F.,Shanghai JiaoTong University | Liu P.,Shanghai University | Ji H.,Shanghai University | Ding Y.,Shanghai Electrical Power Generation Equipment Co. | And 2 more authors.
Materials Characterization | Year: 2014

10%Cr steels are being used in steam power plant due to their excellent properties at high temperatures. Dramatically enhanced impact toughness was obtained in the welded 10%Cr rotor steel after post-weld heat treatment, increasing from 5.0 J for the as-welded material to 37.5 J after being heat treated at 730 °C. Analysis of crystallographic structure showed that the microstructure was transformed from as-welded lath martensite to tempered martensite (treated at 670 °C to 700 °C), and then to high-temperature tempered martensite (treated at over 710 °C). With the increase of treatment temperature, the fractography varied from brittle fracture to a fracture mode with both brittle and ductile fracture features. A small amount of M 7C3 (M = Fe, Cr) particles was found in as-welded metals, while large amounts of M23C6 particles were observed in those after being treated. It is proposed that the microstructure evolution from martensitic laths in the as-welded metals to a softer ferrite matrix with the dispersion of metal carbides led to higher toughness in the post-weld heat treatment materials. © 2014 Elsevier Inc.

Wang C.-D.,Shanghai JiaoTong University | Chen M.,Shanghai JiaoTong University | An Q.-L.,Shanghai JiaoTong University | Wang M.,Shanghai Electrical Power Generation Equipment Co. | Zhu Y.-H.,Shanghai Electrical Power Generation Equipment Co.
International Journal of Precision Engineering and Manufacturing | Year: 2014

Minimum quantity lubrication (MQL) is one of the promising Green Manufacturing Technology to meet the challenge of machining difficult-to-cut material Inconel 182 which is deposited by Shield Metal Arc Welding (SMAW). Unlike the flood lubrication, in MQL, only a small amount of non-toxic biodegradable oil are directly sprayed to the cutting zone by compressed air, which can reduce friction coefficient and temperature. Wear performance of uncoated tool inserts and Physical Vapor Deposition (PVD) coated tool inserts are evaluated by comparison during up and down face milling Inconel 182 with different MQL nozzle positions. Results indicate that uncoated tool inserts are not suitable for face milling Inconel 182 in all lubrication conditions due to the severe flank wear and the catastrophic breakage. On the contrary, PVD coated tool inserts have longer tool life compared to uncoated ones in all lubrication conditions. MQL nozzle positioned at tool cut into workpiece and positioned at tool cut out of workpiece in down milling as well as MQL nozzle positioned at tool cut out of workpiece in up milling can effectively prolong tool life of PVD coated tool inserts, which can be selected as the optimal lubrication solution for face milling Inconel 182. © 2014 Korean Society for Precision Engineering and Springer-Verlag Berlin Heidelberg.

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