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Vol.33, No.12, 1583 ~ 1593, 1995

Title

Microstructure and High Temperature Compressive Properties of Precipitation Hardenable Ni - Cr - Mo - Ti Steel

임차용Cha Yong Lim, 김성준Sung Joon Kim

Abstract

Microstructure and high temperature deformation behavior of austenitic Ni-Cr-Mo-Ti steel have been investigated. This steel was one of the precipitation hardenable Fe-base superalloys which is used for the high temperature applications. Composition of the steel used in this investigation was 26.5Ni-15.9Cr-1.3Mo-2.2Ti(wt.%). The ingot prepared by the vacuum induction melting and electro-slag remelted process was homogenized and hot forged followed by the solution and aging treatments. The main precipitate after aging treatment at 720℃ for 16 hrs was small spherical γ(fcc Ni Ti). Cylindrical compressive specimens of 8mm diameter and 12mm height were machined from the hot forged plates. Compressive tests were carried out in a compression testing machine equipped with a specially constructed testing apparatus. A little changes were observed in the microstructure of specimen surface after compression tests because of the low deformation due to the friction between the specimen and the specimen jig. On the contrary, large changes in the microstructure of center region were caused by the compressive deformation. This deformed structure was dynamically recrystallized at the high temperature of 1000℃ and low strain rate of 10^(-2)sec^(-1). The strain rate sensitivity and activation energy for the hot deformation were also studied.

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