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. Source
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. Source
Wang H.-B.,Harbin University of Science and Technology |
Li D.-H.,Harbin University of Science and Technology |
Hu M.-L.,Harbin University of Science and Technology |
He G.,Harbin Turbine Co.
Jinshu Rechuli/Heat Treatment of Metals | Year: 2010
Fatigue property of 1Cr11NiMoW1 VNbN stainless steel vane used in supercritical steam turbine was investigated. The variation law of tension-press fatigue limit of the specimens under different temperatures was discussed. The morphology of the fracture surfaces was examined by scanning electron microscope. The results show that the fatigue limit of the 1Cr11NiMoW1 VNbN steel changes evidently with the temperature changing. Maximal varying value of tension-press fatigue limit of the test steel under the temperature of 538, 566 and 593 °C. is 81 MPa. Macro-fracture surface of the fatigue specimens includes the crack initiation, the crack extension and the ultimate fracture, and presents obviously crack front edge. Micro-fracture surface presents typical quasi-cleavage fracture characterization. Source
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. Source
Gao J.,Xian Jiaotong University |
Yuan Q.,Xian Jiaotong University |
Li P.,Xian 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. Source