本實驗利用Nd:YAG雷射表面重熔技術(LSM)，搭配不同的雷射功率、離焦長度和掃描速度等參數，針對304沃斯田鐵系不銹鋼之沿晶腐蝕劣化進行表面改質修復。並藉由電化學雙環動電位再活化測試法、殘留應力測量及微結構分析，以評估探討不同雷射參數對LSM去敏化效果及其殘留應力分佈，進而找出最佳的雷射重熔參數區間。
實驗結果顯示，經雷射重熔後之區域中，碳化物能固溶回晶粒，進而改善其IGC抵抗性。從微結構的觀察發現，使用能量密度值越低的參數組合，熔融區的結晶就越細，因此肥粒鐵在此區域的析出也減少。另一方面，搭配殘留應力測量可得知，離焦距離越遠，重熔範圍會因雷射光斑的增大而加寬，且因能量密度的下降導致重熔區的深度也越淺，塑性變形的範圍減少進而所產生之殘留應力也越小；最後利用電化學雙環動電位再活化(DL-EPR)測試其敏化程度(Degree of Sensitization)，結果顯示，在固定的雷射功率下，掃描速率越高，冷卻速率越快，去敏化的效果就越好。歸納所有實驗數據並分析，雷射重熔參數於雷射掃描速率1200mm/min，離焦-20mm之參數組所得效果最佳。
重熔參數改變除可影響實際去敏化之效果及範圍外，亦可能因入熱量或溫度梯度的改變，進而產生新的敏化區域或引入較高的重熔殘留應力，故對敏化之304不銹鋼而言，選用適當的雷射表面重熔參數，才能為敏化不鏽鋼進行較快速及最有效的去敏化修復。

Laser surface melting (LSM) was used to repair the surface layer of sensitized 304 stainless steels. The main concerns in this study were the influence of LSM process parameters on the repairing effect of sensitizatized stainless steels. Electrochemical test and microstructural analysis were used to examine the degree of desensitization. And distribution of residual stress after laser process was studied. LSM process parameters were laser power, defocus length and scanning rate. Optimum condition of process parameters was aim at the effective range of these parameters.
The experimental results showed that the intergranular corrosion resistance in the remelted area was remarkably improved by the redisolution of carbide into the matrix. The laser spot size increased with the increasing defocus length which led to the formation of a thin and broad melted area. As a consequence, the plastic deformation area was narrowed down and residual stress was reduced. The results of double-loop electrochemical potential reactivation test (DL-EPR) showed that the degree of sensitization (DOS) value was decreased with increasing scanning speed. LSM process with its high cooling rate resulted in considerable suppression of Cr-carbide formation. Summarized from the studying results, process condition with laser scanning rate by 1200mm/min and defocus length of -20mm is proven to have satisfactory repairing effect for desensitization of stainless steel components.

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