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Kazemi A.,Islamic Azad University at Tehran | Faghihi-Sani M.A.,Sharif University of Technology | Nayyeri M.J.,Islamic Azad University at Tehran | Mohammadi M.,MAPNA Turbine Blade Engineering and Manufacturing Co. PARTO | Hajfathalian M.,MAPNA Turbine Blade Engineering and Manufacturing Co. PARTO
Ceramics International | Year: 2014

In this work, the effect of zircon content on the mechanical and chemical behaviors of injection molded silica-based ceramic cores has been investigated. In order to simulate a casting process condition, the sintered samples at 1220 C were consequently heated up to 1430 C. Three point bending tests were carried out on all the prepared samples. The chemical resistance of the prepared cores was evaluated by leaching of samples in 43% KOH solution at its boiling point. Phase evolution and microstructure were investigated by XRD and SEM, respectively. Results showed that increasing zircon content led to an increase in MOR and decrease in leachability owing to the decrease in content of fused silica with lower strength and chemical stability. The leaching rate of sintered ceramic cores was decreased after the simulated casting heat treatment at all zircon contents due to crystallization of cristobalite, with a higher chemical stability, on the surface of fused silica particles. © 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Seighalani K.R.,Mapna Turbine Blade Engineering and Manufacturing Company PARTO | Givi M.K.B.,University of Tehran | Nasiri A.M.,Sharif University of Technology | Bahemmat P.,Iran University of Science and Technology
Journal of Materials Engineering and Performance | Year: 2010

Friction stir welding (FSW) parameters, such as tool material, tool geometry, tilt angle, tool rotational speed, welding speed, and axial force play a major role in the weld quality of titanium alloys. Because of excessive erosion, tool material and geometry play the main roles in FSW of titanium alloys. Therefore, in the present work for the first time, tool material and geometry, tool tilt angle, cooling system and shielding gas effects on macrostructure, microstructure, and mechanical properties of pure titanium weld joint were investigated. Result of this research shows that Ti can be joined by the FSW, using a tool with a shoulder made of tungsten (W) and simple pin made of tungsten carbide (WC). The best conditions for welding were use of compressed air as a cooling system, tool tilt angle of 1°, and a stream of Argon as a shielding medium. Investigation on mechanical properties shows that the tensile strength and the yield strength of the welded joint in the best case could be similar to the corresponding strengths of the base metal. © ASM International.

Bahemmat P.,Iran University of Science and Technology | Haghpanahi M.,Iran University of Science and Technology | Givi M.K.B.,University of Tehran | Seighalani K.R.,University of Tehran | Seighalani K.R.,Mapna Turbine Blade Engineering and Manufacturing Company PARTO
International Journal of Advanced Manufacturing Technology | Year: 2012

In the present article, the effect of friction stir welding (FSW) parameters on the weldability and the characteristics of dissimilar weld of aluminum alloys, called AA2024-T4 and AA7075-O are investigated. A number of FSW experiments are carried out to obtain high-quality welds by adjusting the rotational and welding speeds. The weldability and blending of two materials are evaluated by using the macrostructural analysis to observe whether making a notch in a threaded cylindrical tool will lead to a better blend rather than the threaded taper tool or it will have no effects. The mechanical properties of the welds are studied through microhardness distribution and tensile tests. Furthermore, the microstructure analysis is performed to study the influence of the pin profile and the rotational speed on the grain size. Moreover, in the present study, one of the most major goals is to obtain high-quality welds by spending as little expenditure as possible. Therefore, it prevents using complicated and insupportable high welding speed equipments. © Springer-Verlag London Limited 2011.

Mohaghegh K.,FICASABZ | Sadeghi M.H.,Tarbiat Modares University | Abdullah A.,Amirkabir University of Technology | Boutorabi R.,MAPNA Turbine Blade Engineering and Manufacturing Co. PARTO
International Journal of Advanced Manufacturing Technology | Year: 2010

The paper reports the latest outcomes of using design-based reverse engineering on turbine blades. For a long time, the focus of the reverse engineering methods has been the trend toward higher accuracies and faster measurements. Authors introduce a different viewpoint which focuses on design intent of a part. How to reverse engineer a complex shape like a turbine blade is the subject of current research. The attempt toward taking advantage of the construction geometry behind a sample heavy duty turbine blade is thoroughly discussed in three phases. First phase consists of 2D analysis of the reference sections. Then, the stacking axis is introduced as an important non-tangible feature which has the main role to connect the sections in 3D in lean and tilt directions. The third phase uses the concept of blade twist to provide a constraint to define rotational position of the sections with respect to neighbor sections. All the three phases have been applied to different types of original and non-original products which are available in the gas turbine market. The presented comparisons show clearly that the new method of reverse engineering incorporating construction geometry and design intent of the part is quite useful and recognizes many features behind the external geometry which is impossible to follow by the previous conventional methods. The turbine blade 3D model resulted from this new method will have a smooth arc-based surface, straight stacking line passing through turbine axis with maximum section tilt of 0.2 mm and maximum section lean of 0.3 mm to original equipment manufacturer parts and linearly increasing stagger angle from hub to tip which are some of considerable improvements compared to conventional method. © 2009 Springer-Verlag London Limited.

Bozorg Nezhad-Nobijari M.,MAPNA Turbine Blade Engineering and Manufacturing Company PARTO | Isakhani-Zakaria M.,MAPNA Turbine Blade Engineering and Manufacturing Company PARTO | Bakhshi A.,MAPNA Turbine Blade Engineering and Manufacturing Company PARTO
Surface and Coatings Technology | Year: 2016

Internal cooling channels of several first stage serviced blades of a gas turbine were cleaned using conventional chemical picking with acidic and alkaline solutions, as well as with abrasive flow machining, adopted as a novel method serving this purpose, and subsequently aluminized by pack cementation. The effectiveness of the cleaning methods in removing the oxidation products together with the quality of the produced coatings was studied and compared using microstructural analysis and thermal shock tests. The results show that caustic cleaning with a solution of 45 weight percent potassium hydroxide at a temperature of about 150 °C and a pressure of 10 kPa for about 100 h, produces less contaminated coatings with a cleaned surface fraction of about 80%, with no signs of cracks within the coating after thermal shock tests for 100 one-hour cycles at 900 °C. © 2016 Elsevier B.V.

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