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| OXIDATION BEHAVIOR OF Ni-BASED SUPERALLOY K444 AT 900℃ IN AIR DURING LONG TERM |
| GUO Yong'an1, LI Bosong2, LAI Wanhui1, GUO Jianting1, ZHOU Lanzhang1 |
1. Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016
2. School of Materials Science and Engineering, Shenyang University of Technology, Shenyang 110059 |
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Abstract The oxidation kinetic of a Ni-based superalloy K444 at 900℃ in air was studied by thermo gravity (TG) method. The results show that oxidation kinetic of the K444 obeys the parabolic law. The oxide rate constant of the initial stage is greater than steady-state stage, and the turning point is 25 hours. The composition of oxide layer were examined by X-ray diffraction, scanning electron microscopy, energy spectrum analysis and electron probe micro-analyzer. The oxide scale contains several layers: the outer layer of TiO2 mainly; the intermediate layer of Cr2O3 and internal oxidation layer. The growth of oxide scale is controlled by diffusion. The grain boundary segregation and the oxidation of carbide were also observed.
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Received: 25 August 2011
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Corresponding Authors:
ZHOU Lanzhang
E-mail: Lzz@imr.ac.cn.
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