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Vol.41, No.12, 827 ~ 838, 2003
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| Title |
| Effect of S & Mn on the High temperature Cracking and Hot Ductility of Low Thermal Expansion Fe-29Ni-17Co Kovar Alloy |
| 이기안 Lee Gi An , 박종혁 Park Jong Hyeog , 조봉현 Jo Bong Hyeon , 남궁정 Nam Gung Jeong , 김문철 Kim Mun Cheol |
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| Abstract |
| The effect of S & Mn on the hot ductility of Fe-29Ni-17Co Kovar alloy and the mechanism of high temperature cracking occurrence were investigated. It has been found that the brittle intergranular fracture at high temperature cracking is closely associated with the sulfide along grain boundary. Experimental results showed, especially when the S content was high and the Mn content was free, that small cavities could be nucleated easily on FeS particles along grain boundary and propagated fast at high temperature. The hot ductility of Kovar alloy was drastically increased with the addition of Mn and it was also increased with decreasing S content. SEM and FE-SEM analyses showed that the Mn addition in this alloy could cause ductile intergranular fracture appearance below 1150℃ by the precipitation of MnS. It was proposed from the results that the addition of Mn and optimum S content (below 30 ppm) in Kovar alloy was necessary in order to reduce the hot cracking susceptibility. |
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| Key Words |
| Low thermal expansion, Kovar, High temperature brittle intergranular fracture, Hot ductility, S, Mn, FeS |
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