阴极极化对高强度船体结构钢焊缝氢脆敏感性的影响

在恒定阴极电位下利用慢应变速率拉伸试验研究高强度船体结构钢焊缝的电化学性能和力学性能。结果表明，试样拉伸断裂主要发生在焊缝的熔合区；结构钢的阴极极化程度对抗拉强度和屈服强度的影响不大；随阴极电位负移，船体结构钢在海水中的延伸率、断裂时间和断裂应变率逐渐减小, 并且当施加阴极电位为-0.89 V（vs SCE）时各项性能最佳。同时，随着阴极电位负移，断裂方式逐渐从韧性断裂向脆性断裂发展，氢脆敏感性逐渐增加，在 -0.70 V~-0.89 V（vs SCE）之间氢脆敏系数低于5%，不发生氢脆；当电位负于-0.94 V（vs SCE），氢脆敏感性迅速提高，当极化电位为-0.99 V （vs SCE）时氢脆系数显著增大至20%，断口开始出现解理单元细小准解理断裂特征；在负于-1.04 V（vs SCE）时，氢脆系数已高于25%，进入危险区，且断口开始出现较多解理单元粗大的准解理、解理等氢脆断裂特征；随着电位继续负移至-1.14 V（vs SCE），断口完全出现解理组织、沿晶、穿晶结构或者两者混合的氢脆断裂特征。

EFFECTS OF CATHODIC POLARIZATION ON THE HYDROGEN EMBRITTLEMENT SENSITIVITY OF WELDING LINE IN HIGH STRENGTH HULL STRUCTURAL STEEL

Electrochemical properties and mechanical properties of welded high strength steel were investigated by the slow strain rate test (SSRT) method with applied constant cathodic potential. During tensile process the fracture occurred mainly in the weld fusion zone. There was no correlation between maximum tensile strength, yield strength, strength at failure, and hydrogen embrittlement. However, the elongation rate, time-to-fracture and strain-to-failure rate decreased with shifting potential of the negative direction. And the elongation rate, time-to-fracture and strain-to-failure rate displayed the highest values when the potential was -0.89 V (vs SCE). As the cathode potential shifted negatively, the fracture mode gradually shifted from ductile fracture to brittle fracture, and also the sensitivity of hydrogen embrittlement gradually increased. When the polarization potentials between -0.70~-0.89 V (vs SCE), the hydrogen embrittlement coefficient were less than 5%, the hydrogen embrittlement did not occured. When it was negative to -0.94 V (vs SCE), the hydrogen embrittlement susceptibility rapidly increased, while when the polarization potential was -0.99 V (vs SCE), the hydrogen embrittlement coefficient closed to 20% and the fracture surface exhibited some small cell cleavage characteristics of quasi-cleavage fracture. When the polarization potentials were negative to -1.04 V (vs SCE), the hydrogen embrittlement coefficient were more than 25%, and the material reached into the dangerous zone. The surface of fracture appeared more thick cell cleavage characteristics of quasi-cleavage, and cleavage fracture of hydrogen embrittlement. When the polarization potentials negative to -1.14 V (vs SCE), the specimen occured mainly cleavage organization, intergranular, transgranular structure or combination of the two of brittle fracture characteristics of hydrogen embrittlement.