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Vol.43, No.4, 298 ~ 306, 2005
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| Title |
| A Study on Surface Properties and High Temperature Oxidation Behavior of Ion Nitrided FC-25 Gray Cast Iron |
| 허인창 In Chang Hur , 손근수 Kun Su Son , 윤재홍 Jae Hong Yoon , 조동율 Tong Yul Cho , 박봉규 Bong Gyu Park , 김현수 Hyun Soo Kim , 김인수 In Soo Kim |
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| Abstract |
| Surface properties and high temperature oxidation behavior were investigated for FC-25 Gray Cast Iron(GCI) and the ion nitrided GCI(N-GCI). The GCI was pre-cleaned to improve hardness to the optimum pre-sputtering parameters with an Ar/H₂ ratio of 1/2, working pressure of 3 torr, working temperature of 550℃ and working time of 1hour. The optimum nitriding conditions for the maximum hardness of 560575 Hv were an N₂/H₂ ratio of 3/1, working pressure of 3 torr, and working temperature of 575℃. The thickness of graphite in the GCI was increased by increasing the working temperature from 525℃ to 595℃ for the nitriding time of 6-18hrs. XRD patterns showed FeO and Fe₂O₃ peaks for both the oxidized N-GCI and GCI at temperatures of 600℃ and 800℃ under atmospheric environment for both 24 and 60hours. At 800℃, above the Fe4N decomposition temperature of 680℃, the oxidation rate of N-GCI was greater than that of the GCI. The most abundant nitride, Fe4N, was decomposed and the nitrogen gas given off by the decomposition made the protective film porous by degassing through the film. But at 600℃, below the decomposition temperature, the degree of oxidation of N-GCI was lower than that of the GCI because the nitride film worked as protective barrier for oxidation. (Received October 29, 2004) |
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| Key Words |
| FC-25 gray cast iron, Ion nitriding, Surface property, High temperature oxidation |
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