為防止核電廠圍阻體覆銲處於銲接製程中產生裂紋，本文旨在針對添加不同Nb含量之鎳基Alloy 52銲材，進行銲接性、凝固裂紋敏感性、DDC敏感性與耐腐蝕性的討論。實驗使用GTAW銲接程序，檢視不同比例Nb添加對於稀釋率的影響，藉由橫向拘束試驗，研究銲件凝固裂紋敏感性，並以顯微組織觀察與成分分析，觀察銲件冶金行為變化，最後利用單環動電位再活化技術(SL-EPR)與惠式試驗法(M-Huey Test)，檢驗並綜合討論微組織變化對耐腐蝕性的影響。
在橫向拘束試驗結果上，以添加2.53% Nb銲件之凝固裂紋敏感性最高，這是由於銲件添加2.53% Nb使得Laves+ϒ共晶相析出降低凝固溫度，增加固液相共存區間，而使熱裂敏感性提高；添加0.02% Nb銲件之DDC敏感性最高，因Nb添加稀少，銲件晶界缺乏中等尺寸之NbC析出物釘扎(Pinning)，而於覆銲時晶界產生遷移、滑移與類似潛變的現象。
比較不同Nb添加量銲道的微觀組織結果顯示，無Nb之52合金，主要由胞狀枝晶構成，於覆銲時因無法限制晶界遷移，而容易產生DDC；而添加Nb之銲件主要則是由柱狀枝晶與等軸晶構成，隨著Nb含量增加，析出物NbC粗大化情形就越明顯。
在腐蝕試驗上，Alloy 52因遷移晶界受阻於TiN而產生晶界缺鉻，造成沿晶腐蝕的情形；隨著Nb的增加，NbC粗大化情形增加，造成局部伽凡尼效應而產生蝕孔現象，抗腐蝕性降低。

This study investigates the weldability, solidification cracking susceptibility, ductility-dip cracking(DDC) susceptibility and corrosion resistance of Inconel Alloy 52 with different Niobium(Nb) content. By GTAW process, different dilution rates with different Nb content weldments were studied. Trans. Varestraint Test was used to predict the solidification cracking susceptibility. Microstructure and EDX analysis was used to realize the change of metallurgical behavior. Finally, combine the above results, the corrosion resistance was discussed after SL-EPR and Modified Huey Test.
After the Trans. Varestraint Test, it was indicated that the susceptibility of solidification cracking in 2.53% Nb weldment is the highest,. Because of the eutectic Laves phase precipitating, it lowers the melting temperature and increase the size of the crack susceptible solid + liquid mushy zone. Besides, the sensitivity of ductility-dip cracking in 0.02% Nb weldment is the highest. Due to the lack of extensive GB pinning by the medium size eutectic NbC-like precipitates, it cause GBs migrating, sliding and creep-like phenomenon in cladding.
Inspection on the fusion zone of weldments with different Nb content, it was shown that the alloy 52 without Nb content was cellular dendrite mainly. Owing to the unrestrained grain boundary migration in cladding, the DDC phenomenon occurred often at alloy 52. The alloy 52 with Nb content was columnar and equiaxed dendrite. The more Nb, the bigger size of eutectic NbC-like precipitates.The results of corrosion displayed that the alloy 52 weldment has worse IGC resistance because the entectic TiN precipitated at GBs. The more Nb content, the worse corrosion resistance because of the galvanic effect when the size of NbC is becoming bigger.

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