破裂機構中應力腐蝕破裂和氫脆的諧和效應

Synergistic Effects of Stress Corrosion Cracking and Hydrogen Embrittlement in Fracture Mechanism

本文藉材料破損分析來探討應力腐蝕破裂（SCC）和氫脆（HE）兩者間之關連性。研究方法包括破斷面觀察、腐蝕生成物分析及內耗測試。結果發現：316不銹鋼保護管破裂以穿晶型態為主，破斷面有羽毛狀及劈裂狀破壞組織，表面腐蝕生成物大多為氯化物。而內耗實驗證實破裂管材具有較高的氫峰，且離破裂端愈近，氫峰愈強。綜合實驗結果，破壞機構主要為氯離子誘發孔蝕，或低pH值發生腐蝕溶解，破壞表面鈍化膜，而產生SCC特徵，控制裂縫起始過程；HE使原子鍵結失去結合力而變脆，參與裂縫傳播步驟。兩者關係具加成作用，並不互相排斥，故破斷面有明顯穿晶應力腐蝕破裂（TGSCC）特徵，卻同時含有較高之氫吸收量。

Roles of stress corrosion cracking (SCC) and hydrogen embrittlement (HE) in fracture mechanism have been investigated in this paper. The experimental methods included fracture morphology observation, corrosion products analysis, and internal friction measurement. The results showed that the fracture mode of 316 stainless steel tube was transgranular type with feather-like and cleavage-like facets. The chloride was the main corrosion products on the failure surface. On the other hand, internal friction verified the high hydrogen peak and S-K peak in the rupture pipe. The closer the sample from rupture end, the stronger the intensity of hydrogen peak was. According tothe results, the fracture mechanism could be divided into two parts. The initiation of crack was controlled by SCC, chloride corroding the passive film or low pH value inducing anodic dissolution. The propagation of crack was joined with HE, hydrogen decohering the bonding force of atoms. The relationship between SCC and HE was synergistic. Therefore, the failure tube demonstrated both TGSCC on the fracture surface and higher hydrogen content in the structure.