Refurbishment on Superalloy Hot Components of Gas Turbines
|摘要:||本研究針對燃氣渦輪機熱段組件之再生性進行研究。第一部份的研究為應用轉移式電弧電漿銲接 (Plasma Transferred Arc Welding; PTA) 進行修補銲。研究結果顯示，經高溫高壓環境操作後之IN-738LC超合金組件，於銲前先進行固溶處理後，可得穩定的銲接性。扭伸試驗結果顯示，所有的銲接試片不論在室溫或高溫 (760℃和980℃) 扯伸條件，都斷裂在基材位置。再生銲件的循環氧化試驗結果顯示出鋅道的氧化曲線相似於基材。
第二部份的研究則針對寬間距活性擴散硬銲 (Activated DiffusionBraze; ADB) 使用三種不同硬銲填料，進行再生性的評估。填料在基材表面的潤濕性試驗結果顯示，當填料具有較低程度的潤濕性時，乃起因於與基材間快速的等溫凝固作用；相對的，良好的潤濕作用起因於與基材間較為遲鈍的等溫凝固作用。扯伸試驗結果顯示，添加金屬混合40wt%DF4B硬銲填料使用1190℃硬銲溫度的ADB試片，其常溫扯伸強度為基材強度的85%，980℃扭伸強度值幾乎等於基材的強度；但ADB試片的伸長率皆低於基材的扭伸值。循環氧化測試結果顯示，使用Nicrobraz 150為填料的ADB試片，在第150小時循環後出現明顯衰退現象，而DF4B和BRB的ADB試片至205小時循環後，仍未出現明顯的衰退。|
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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