本實驗採用2.5kW Nd:YAG雷射，進行沃斯田鐵型不銹鋼敏化之修復技術研究。研究利用雷射進行表面重熔並探討不同操作參數下(雷射功率、掃描速度及離焦距離)，對304敏化不銹鋼沿晶腐蝕(IGC)抵抗性的影響。實驗採用惠氏試驗法(Huey test)，評估經重熔後試件之沿晶腐蝕抵抗性，並配合熱循環溫度(Thermal cycle)及殘留應力量測，進而了解雷射表面重熔對於試件整體之影響。
實驗結果顯示，經重熔後之區域可使得原先敏化之微結構達到去敏化作用，進而改善其IGC抵抗性。理由是雷射表面重熔具有相當高的峰值溫度和快速冷卻速率，導致晶界中的碳化鉻析出物被重新溶解和抑制，達到改質之作用，且重熔區之寬度隨著雷射功率或離焦長度的提高而顯著增加。而重熔入熱所產生之熱影響區，因其於峰值溫度950oC以上區間產生碳化物固溶作用，故於重熔區兩側因參數變化將產生尺寸不等之重熔保護區，討論此區域對沿晶腐蝕抵抗性，亦能得到優於敏化區間之結果。
而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。

A practical repairing technique of laser surface melting (LSM) was performed on sensitized 304 stainless steel surface using a 2.5kW Nd:YAG laser. The main concerns in this study were the effects of LSM parameters, such as, laser power(1000~1500W), traveling speed(200~1200 mm/min) and defocus length(0~-20 mm) on the intergranular corrosion (IGC) resistance of sensitized 304 stainless steel. The IGC susceptibility of specimens was evaluated by the Huey test.
The experimental results showed that with the use of the LSM, the sensitized microstructures were effectively desensitized or repaired. The improved IGC resistance in the laser melted zone (LMZ) and heat affected zone (HAZ) compared to the rest un-melted area was apparent. This was due to the very high peak temperature and rapid cooling rate during LSM process which caused the Cr-carbide precipitates to be dissolved and suppressed at the refined sub-grain boundaries in the LMZ and HAZ. The width of laser melted zone was increased significantly with the increase of laser power or defocus length. LSM is proven to be a powerful effective method for repairing the sensitized 304 stainless steel.

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