Refurbishment on Superalloy Hot Components of Gas Turbines
博士 === 國立交通大學 === 機械工程研究所 === 86 === Superalloy hot section components of gas turbines were refurbished by long term high-temperature and high-pressure operation. Plasma transferred arc welding (PTA) technique was evaluated in phase I of this study. Experimental results showed that the weldabil...
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| Format: | Others |
| Language: | zh-TW |
| Published: |
1998
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| Online Access: | http://ndltd.ncl.edu.tw/handle/42715897347763706078 |
| Summary: | 博士 === 國立交通大學 === 機械工程研究所 === 86 === Superalloy hot section components of gas turbines were refurbished by long term high-temperature and high-pressure operation.
Plasma transferred arc welding (PTA) technique was evaluated in phase I of this study. Experimental results showed that the weldability of IN-738LC components is stable after pre-weld solid solution heat treatment. Results of tensile test showed that PTA welded specimens exhibited 96% of nominal tensile strength of IN-73 8LC base material. Fracture was occurred predominantly in the base materials instead of in the heat-affected zone (HAZ) for gas tungsten arc weld (GTAW) repaired weidments. The results of anti-cyclic-oxidation of PTA welded specimen is similar to that of the base material.
In phase II of this study, wide-clearance activated diffusion brazed (ADB) techniques were applied to restore worn areas of superalloy components with three kinds of nickel-base braze alloys as filler material. Tests on the wettability of the braze alloys associated with the IN-73 8LC surface showed that a low degree of wetting was related to a rapid onset of isothermal solidification and conversely a high degree of wetting was associated with a relatively low rate of isothermal solidification. The results of tensile test showed that ADB specimens using the parameters of 40wt% DF4B and 1190℃ braze temperature exhibited 85% tensile strength of IN-738LC base materials at room temperature and retain the same strength of base material at 980℃. However, the ductility can be reduced for ADB specimens using all three filler metals. The results of cyclic-oxidation test showed that ADB specimens using Nicrobraz 150 as a brazes alloy were decayed after 150 cycles. However, the ADB specimens using DF4B or BRB had no obvious decay until 205 cycles.
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