High-Temperature Compression Behavior of Cast and Homogenized IN939 Superalloy
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INTRODUCTION
ONE of the most important properties of metals and alloys is their high capability to plastic deformation. Most of the superalloys are resistant to deformation and this property is one of their useful characteristics, especially at high temperatures. During hot working of superalloys, phenomena such as strain hardening, dynamic recovery (DRV), dynamic recrystallization (DRX), grain growth, and dynamic precipitation occur simultaneously. Controlling parameters affecting the hot working process, hence microstructure and mechanical properties in the final deformed material, are a critical issue. During hot deformation, temperature, strain rate, and the amount of strain are the most important parameters affecting the microstructure and mechanical behavior of the alloy.[1,2] High-temperature tensile, compression, torsion, and rolling tests are generally used to evaluate hot deformation behavior of materials. The high-temperature compression test is frequently used for investigation of the hot deformation behavior of superalloys.[3–10]
M.R. JAHANGIRI, PhD Student, is with the School of Metallurgy and Materials Engineering, Iran University of Science and Technology, IUST, Tehran 16846-13114, Iran, and also with the Metallurgy Department, Niroo Research Institute, Tehran 14686, Iran. Contact e-mail: [email protected] H. ARABI and S.M.A. BOUTORABI, Professors, are with the School of Metallurgy and Materials Engineering, Iran University of Science and Technology. Manuscript submitted June 20, 2012. Article published online December 11, 2012 METALLURGICAL AND MATERIALS TRANSACTIONS A
IN-939* is a precipitation-strengthened Ni-Cr-Co *IN939 is a trademark of Special Metals Corp., Huntington, WV.
superalloy with excellent mechanical properties and good corrosion/oxidation resistance. It is currently used for manufacturing of blades/vanes, fuel nozzles, retaining rings, diffusers, and other structural components of industrial and jet gas turbines.[11–13] Due to the presence of high amounts of chromium (22.5 wt pct) in its chemical composition, IN939 is one of the most corrosion-resistant nickel-base superalloys in oxidizing and sulfurizing atmospheres at high temperatures. To the best of our knowledge, no data have been published so far on the effects of thermomechanical parameters on the hot deformation behavior of IN939 superalloy during the high-temperature compression test. The reported information is commonly about the effects of casting and heat treatment parameters on the microstructure and mechanical properties of the alloy,[14–18] as well as the creep and fatigue mechanisms of this alloy.[19,20] In addition, there are some reports about the welding properties of this alloy.[21] The wrought version of IN939 superalloy was developed recently by Jahangiri et al.[22] The purpose of this work was to study the hightemperature deformation behavior of IN939 superalloy and to investigate the influence of different variables on the stress-strain curves and microstructural changes during the compression tests. The power,
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