雷射表面重熔處理對Alloy52覆銲之效果研究TheEffectof.PDF

雷射表面重熔處理對Alloy 52覆銲之效果研究 The Effect of Laser Surface Treatment on Alloy 52 黃証羣 、李驊登* 、王怡茹、吳函諭 Chang-Chun Huang, Hwa-Teng Lee*, Yi-Ju Wang and Han-Yu Wu 國立成功大學 機械工程系 教授 國立成功大學 機械工程系 研究生 National Cheng Kung University Department of Mechanical Engineering *通訊: htlee@mail.ncku.edu.tw 摘要 本研究利用熱處理模擬核電廠覆銲融填之鎳基Alloy 52 銲材，在不當銲接或高溫環境長時間使用後，晶界 生成富 Cr 碳化物使耐腐蝕性降低之情形，再以不同能量密度的雷射光束對覆銲層進行雷射表面重熔(Laser Surface Melting, LSM)以探討最佳雷射參數。實驗使用高速鑽孔法討論表面殘留應力導入程度，並藉由惠式試驗 法(M-Huey Test)及雙環動電位再活化法(DL-EPR)與微結構分析討論抗腐蝕能力提升程度。 實驗結果顯示，不同能量密度引入之殘留應力皆小於降伏強度，並對耐蝕性無顯著影響 ．而熱處理後之試 件經由LSM將富Cr及富Ti碳化物重熔回基地，並形成緻密枝晶結構，大幅提升抗腐蝕能力，但使用低能量密度 時熱影響區內因析出物未完全熔融而有孔蝕情形，因此本研究建議用於Alloy 52 表面處理之雷射重熔為能量密 度為較高的24.44J/mm2 。 關鍵字：Alloy 52 、雷射表面重熔、沿晶腐蝕、殘留應力 Abstract Laser Surface Treatment (LST) is used to repair the surface of overlaid nickel based metal Alloy 52 in this study. In simulating of welding decay by aging heat treatment, chromium carbide had precipitated in grain boundary, caused the decrease of corrosion resistance. Laser Surface Melting (LSM) is now considered to be a solution of grain boundary segregation. In addition to the investigation of metallurgic, Modified Huey Test and DL-EPR were applied to evaluate the improvement of corrosion resistance. Surface Residual Stress was examined by High-Speed Hole-Drilling strain gauge method. In comparison with As-Welding (AW), LSM had increased the surface tensile residual stress, but still lower than its own yielding stress. Metallurgic showed that chromium and titanium carbide were resolved and redistributed in melting zone, which made the intergranular and interdendritic corr