대한용접접합학회:학술대회논문집 (Proceedings of the KWS Conference)
- 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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- Pages.235-243
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- 2002
WELD REPAIR OF GAS TURBINE HOT END COMPONENTS
- Chaturvedi, M.C. (Department of Mechanical and Industrial Engineering University of Manitoba) ;
- Yu, X.H. (Department of Mechanical and Industrial Engineering University of Manitoba) ;
- Richards, N.L. (Department of Mechanical and Industrial Engineering University of Manitoba)
- 발행 : 2002.10.01
초록
Ni-base superalloys are used extensively in industry, both in aeroengines and land based turbines. About 60% by weight of most modern gas turbine engine structural components are made of Ni-base superalloys. To satisfy practical demands, the efficiency of gas turbine engines has been steadily and systematically increased by design modifications to handle higher turbine inlet or firing temperatures. However, the increase in operating temperatures has lead to a decrease in the life of components and increase in costs of replacement. Moreover, around 80% of the large frame size industrial/utility gas turbines operating in the world today were installed in the mid-sixties to early seventies and are now 25 to 30 years old. Consequently, there are greater opportunities now to repair and refurbish the older models. Basically, there are two major factors influencing the weldability of the cast alloys: strain-age cracking and liquation cracking. Susceptibility to strain-age cracking is due to the total Ti plus AI content of the alloy; Liquation cracking is due either to the presence of low melting constituents or constitutional liquation of constituents. Though Rene 41 superalloy has 4.5wt.% total Ti and Al content and falls just below the safe limit proposed by Prager et al., controlled grain size and special heat treatments are needed to obtain crack-free welds. Varying heat treatments and filler materials were used in a laboratory study, then the actual welding of service parts was carried out to verity the possibility of crack-tree weld of components fabricated from Rene 41 superalloy. The microstructural observations indicated that there were two kinds of carbides in the FCC matrix. MC carbides were located along the grain boundaries, while M