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Chen Z.,Harbin Engineering University | Zhao X.,Harbin Turbine Co. | Hao W.,Harbin Engineering University | Li Z.,Harbin Turbine Co.
Harbin Gongcheng Daxue Xuebao/Journal of Harbin Engineering University | Year: 2012

To prevent scuffing of bolts in a steam turbine cylinder at a high temperature, the salt bath chromizing process of 1Cr11MoNiW1VNbN steel was studied. The microstructure of the chromizing layer was observed by optical microscopy (OM) and scanning electron microscopy (SEM). The hardness, elastic modulus, and toughness were obtained by a micro-hardness and nano-hardness tester. The wear resistance was evaluated by pin-on-disk wear tests. Potentiodynamic polarization curves and high-temperature oxidation tests were conducted to investigate the corrosion behavior. The results indicate that the chromized layer consists of Cr23C6 and Fe-Cr (columnar grains) phases after salt-bath chromizing and subsequent heat treatment and exhibits lower hardness and elastic modulus but higher toughness. The salt bath chromizing process is expected to be an effective way to prevent bolts from scuffing at high temperatures due to it significantly improved wear resistance, electrochemical corrosion resistance, and high temperature oxidation resistance.

Zhang S.,Shenyang University of Technology | Wang D.,CAS Shenyang Institute of Metal Research | Peng J.,Harbin Turbine Co.
Jinshu Xuebao/Acta Metallurgica Sinica | Year: 2016

Up to now, considerable effort has been expended in attempts to investigate the influences of Re on Ni-based single crystal superalloys. However, few study had elucidated the influences of Re on carbide, boride and grain boundary. Therefore, the influence of a 2%Re (mass fraction) addition on the as-cast and heat-treated microstructures of a Ni-based directionally solidified superalloy was investigated by comparison with Re-free alloy using SEM, EPMA and TEM. The results show that Re accelerates the precipitation of μ phase in the periphery of eutectic and at grain boundary for as-cast microstructure. After heat treatment, Re also accelerates the precipitation of phase in the vicinity of primary MC carbide and at grain boundary. For 0Re alloy, there are small number of M6C carbide in the vicinity of primary MC carbide and M23(C, B)6 boro-carbide at grain boundary. For 2Re alloy, a large amount of blocky μ phase enveloped by thick γ'-film is found in the vicinity of primary MC carbide and at grain boundary. Enrichment of B along the grain boundary is observed in 0Re alloy. On the contrary, relatively uniform distribution of B is found in 2Re alloy. The precipitation mechanism of μ phase during the process of heat treatment is also analyzed. © All right reserved.

Zhang H.,Harbin Institute of Technology | Zhang H.,Harbin Turbine Co. | Wang X.,Harbin Institute of Technology | Yan P.,Harbin Institute of Technology | Han W.,Harbin Institute of Technology
Jixie Gongcheng Xuebao/Journal of Mechanical Engineering | Year: 2012

The structure feature aerodynamic characteristics, sealing mechanisms and sealing effect of labyrinth seal and leaf seal are numerically studied under same condition, the difference of two kinds seals is compared. The reliability of commercial computational fluid dynamics computational code CFX is validated by using the experimental data from literature. The performance curves of computation has a good agreement with the experimental data, the numerical simulation method is feasible. Numerical simulation on the flow field of the labyrinth seal and leaf seal are carried out respectively by using the commercial software CFX. Through comparison analysis based on the calculation results of the two type seals, their sealing mechanisms is described, the sealing characteristics and the friction torque variation law of their own are given. The analysis results show that, the radial clearance of leaf seal is much smaller than the labyrinth seal, its leakage flow rate is about 1/3 labyrinth seal's, and the friction resistance torque on the rotation axis is lower than the labyrinth seal. Because of the superiority of the leaf seals in structure operation characteristics and aerodynamic performance, leaf seals may replace labyrinth seals in the near future.

Zhao X.,Harbin Turbine Co. | Li Z.,Harbin Turbine Co. | Xu B.,Harbin Turbine Co. | Chen Z.,Harbin Engineering University
Jinshu Rechuli/Heat Treatment of Metals | Year: 2012

Microstructure and properties of chromized layer of R26 alloy was observed by OM, SEM, micro-hardness, pin-on-disk wear tests, cyclic polarization curves and high-temperature oxidation tests. The results show that the chromized layer consists of Ni-Cr-Fe, NiCoCr, Ni 3Al, (Cr, Co, Ni) 23C 6 and (Cr, Fe) 7C 3 phases after salt-bath chromizing and subsequent heat treatment, and exhibits higher hardness, lower friction coefficient and wear rate, the depth of chromized layer is about 15 μm. The salt bath chromizing process is expected to be an effective way to prevent bolts from scuffing at high temperature due to it significantly improved electrochemical corrosion resistance and high temperature oxidation resistance.

Zhao Y.-H.,Harbin Engineering University | Zhao Y.-H.,Harbin Turbine Co. | Zhao C.-Z.,Harbin Engineering University | Wang J.-N.,Harbin Engineering University | And 2 more authors.
Kang T'ieh/Iron and Steel | Year: 2013

The effect of chemical compositions and heat treatment normalizing temperature on δ-ferrite content was investigated to analyze the forming mechanism of δ-ferrite through thermo-calc thermodynamic equilibrium phase calculations and quantitative metallographic analysis, mechanical property test, SEM analysis. The effect of content and position distribution of δ-ferrite on impact energy was also analyzed. The results show that chemical compositions and normalizing temperature have obvious effect on δ-ferrite content. δ-ferrite content will decrease with increase in C and N content. The δ-ferrite mainly concentrates in the prior austenite grain boundary, which can decrease impact energy. There are the large aggregations of rich Nb cabide, which can decrease MX phase content.

Han R.D.,Harbin Institute of Technology | Wang H.,Harbin Institute of Technology | Zhang Y.,Harbin Institute of Technology | Yao Q.W.,Harbin Turbine Co.
Applied Mechanics and Materials | Year: 2010

The machinability of nickel-based superalloy GH4169 is very poor, the traditional machining of GH4169 using the cutting fluids with the active additives causes environmental and health problems, which is out of the request of the sustainable development strategy. In this paper a new green cutting technology with overheated water vapor as coolants and lubricants was proposed to achieve the aim of green cutting and high productivity. Cutting experiments and tool wear tests using carbide tool YG6 under dry cutting, emulsion and water vapor were performed. The cutting force, cutting temperature, machined surface quality and tool life were investigated; the curve of flank tool wear and relation between tool life and cutting velocity was carried out. The results of experiments indicated that during water vapor condition, the cutting force and cutting temperature was reduced, the machined surface roughness was improved, and the tool life was longed, respectively, and the higher velocity was taken during the some tool wear condition compared to dry cutting. The research results show that green cutting was achieved associated with overheated water vapor cooling and lubricating, at he same time the machined surface quality and production efficiency was increased. © (2010) Trans Tech Publications.

Li D.,Harbin Institute of Technology | Yu D.,Harbin Institute of Technology | Liu J.,Harbin Turbine Co.
Proceedings - 2011 International Conference on Future Computer Sciences and Application, ICFCSA 2011 | Year: 2011

This Paper described a new algorithm for round contour extraction of indent image on metal surface after Brinell hardness test. Morphological theory was employed to extract round contour of indent image effectively. Based on characteristic of grayscale image, structural element was chose according to its shape feature and grayscale feature in order to acquire better result. Before the stage of contour extraction, fuzzy theory was employed to enhance indent image. Validity of this approach is demonstrated using several indent images. © 2011 IEEE.

Gao J.,Xi'an Jiaotong University | Yuan Q.,Xi'an Jiaotong University | Li P.,Xi'an Jiaotong University | Zhang H.-T.,Harbin Turbine Co. | Lv Z.-Q.,Harbin Turbine Co.
Zhendong yu Chongji/Journal of Vibration and Shock | Year: 2012

Gas turbine rotors are usually assembled with several laminated wheels and tie bolts, the contact surfaces of the wheels are grinded. Roughness measurements on grinded wheel surfaces of a tested rod-fastened rotor show that they have two different fractal structure regimes. Here, the fractal dimension D 1, D 2 and roughness parameter G 1, G 2 of each bifractal surface profile were calculated with the structure function method. The bifractal geometry was used to describe the surface topography and the tangential stiffness of contacting asperities was derived with Hertz contact theory. The tangential contact stiffness of an elastic-plastic bifractal surface was the sum of stiffnesses of all elastic micro-contacts. The torsional stiffness of a roughness layer formed with contacting asperities was modeled as a torsional spring between contact wheels. The torsional modal frequencies of the rod-fastened rotor under different preloads were obtained through both 3-D finite element modal analysis and experimental modal analysis. The torsional stiffness of the roughness layer was identified from the above results and its theoretical torsional stiffness was consistent with the test data. It was shown that the proposed bifractal model for the torsional stiffness of a roughness layer is reasonable and effective to consider influence of contact effects on torsional vibration modal frequencies.

Tang H.,Harbin Engineering University | Zhao C.-Z.,Harbin Engineering University | Luo F.,Harbin Engineering University | Wei S.-S.,Harbin Turbine Co.
Journal of Iron and Steel Research | Year: 2011

The equilibrium phases from 400-1600 °C were calculated by means of thermo-Calc software. The carbide powder was made by the methods of electrochemical extraction. The morphology observation and analysis of XRD were performed. The results show that the equilibrium phases precipitated from 400-1600 °C of the steel are MX, M 23C 6 and Laves, which corresponds to the precipitating temperature of 1190, 880 and 780 °C respectively. The carbides of MX type are NbC and NbN rich in Nb, those of M 23C 6 type are Cr 23C 6 rich in Cr. The size of carbides is between 50-100nm. Its shape is irregular spherical and column, which dispersed in the matrix of the steel.

Yuan C.,CAS Shenyang Institute of Metal Research | Guo J.-T.,CAS Shenyang Institute of Metal Research | Li G.-S.,CAS Shenyang Institute of Metal Research | Zhou L.-Z.,CAS Shenyang Institute of Metal Research | And 2 more authors.
Zhongguo Youse Jinshu Xuebao/Chinese Journal of Nonferrous Metals | Year: 2011

The resent work in the Department of Superalloys and Itermetallic Composites, Institute of Metal Research, about the effect of nitrogen (N) on the microstructure and properties of cast superalloys was summarized. The control of N cast superalloys melting process was discussed. The results show that N content increases with the increase of Cr content in the virgin alloys, and the increment of recycle times or revert proportion in reverted alloys. Increasing N content considerably reduces the mechanical properties of both cast Ni-based superalloys and Co-based superalloys. In cast Ni-based superalloys, N reacts mainly with Ti to form TiN particles in the melt, which acts as profuse nucleus for subsequent carbides nucleation and growth at a higher temperature than in the normal solidification. These blocky carbides with large size can block the dendrite channels, and reduce the fluidity of the final liquid fraction and the permeability of the solidification structure. Consequently, increasing N content results in a greater degree of microporosity, which leads to a significant decrease in the mechanical properties of cast Ni-based superalloys. In Co-based superalloy, high N content will extend the solidification window during the solidification process, and then leads to the coarse carbide eutectic structure by increasing the quantity of the interdendritic Cr7C3 carbide eutectic, which restrains the M23C6 particles precipitates in the interdendritic regions. This microstructure is conducive to promote the initiation and propagation of the cracks and decrease the mechanical properties of cast Ni-based superalloys.

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