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Vol.35, No.9, 1244 ~ 1254, 1997
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| Title |
| Microstructure and High Temperature Low cycle Fatigue Behavior of Friction Welded Nimonic 80 A / Heat Resistant Alloy Component |
| 김송희 , 함종오 , 윤여범 , 박노광 S . H . Kim , J . O . Ham , Y . B . Yun , N . K . Park |
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| Abstract |
| The low cycle fatigue properties and microstructures of Nimonic80A/SNCRW and Nimonic80P,/X45CrSi93 friction weldments were characterized to know whether friction welding techniques could be applied to reduce the cost of MTU diesel engine valves. Fatigue crack which initiated from the interface between SNCRW steel and the HAZ advanced towards SNCRW. It is dued to the weakening of SNCRW steel occurred by grain growth during postweld heat treatment (700℃, 16hrs) which is purposed to re-precipitate the resolved γ phase in the HAZ during welding to recover strength. The fatigue cracking of Nimonic80A/X45CrSi93 friction weldments initiated from the X45CrSi93 steel side. Superior fatigue resistance were obtained in Nimonic80A/X45CrSi93 weldment than Nimonic80A/SNCRW weldment. The reason was due to, in the HAZ of Nimonic80A/X45CrSi93, the fine spherical carbides (M_7C₃) precipitated at grain boundary and within grain. However, in the HAZ of Nimonic80A/SNCRW, the carbides (M_(23)C_6) precipitated along coarse grain boundaries during friction welding and post weld heat treatment could cause to decreased fatigue strength. |
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