EH36钢焊接接头预腐蚀下的疲劳性能及断裂机制研究

Research on Corrosion Fatigue Performance and Fatigue Fracture Mechanism of Pre-corrosion EH36 Steel Welded Joints

通过盐雾腐蚀试验和腐蚀疲劳试验研究不同盐雾腐蚀时间下EH36钢焊接接头的腐蚀疲劳性能。在盐雾环境中,试样的腐蚀产物主要为FeOOH、Fe_(2)O_(3)和Fe_(3)O_(4),试样表面出现了大量的点蚀坑,盐雾腐蚀速率和最大点蚀坑深度随腐蚀时间的增大而增大。对比不同盐雾腐蚀时间下试样的腐蚀疲劳寿命发现,盐雾腐蚀后疲劳试样的寿命降低35%~77%,盐雾腐蚀时间对试样腐蚀疲劳性能的影响随应力范围的降低而增大。试样疲劳断口形貌显示,未经盐雾腐蚀处理的疲劳试样和盐雾腐蚀疲劳试样的腐蚀疲劳裂纹都萌生于裂纹源区内EH36钢焊接接头表面的点蚀坑。前者表面的点蚀坑由腐蚀和应力的共同作用产生,后者表面的点蚀坑在盐雾腐蚀过程中产生。两种试样的裂纹扩展区瞬间断裂区的微观形貌相似。盐雾腐蚀对腐蚀疲劳性能的影响主要体现在盐雾腐蚀产生的点蚀坑降低了疲劳试样的裂纹萌生寿命。

The corrosion fatigue performance of EH36 steel welded joints with different salt spray corrosion time were studied by salt spray corrosion test and corrosion fatigue test.According to the results of salt spray test,the corrosion products of the specimen were FeOOH,Fe_(2)O_(3)and Fe_(3)O_(4)and a large number of pits distributed on the surface of the specimen.The salt spray corrosion rate and the maximum pitting depth increased with corrosion time.Comparing the corrosion fatigue life of specimens with different salt spray corrosion time,it was found that the life of specimens after salt spray corrosion was reduced 35%-77%.The influence of salt spray corrosion time on the corrosion fatigue performance increased with the decrease of stress range.The fatigue fracture morphology of the specimens showed that the corrosion fatigue cracks of the specimens without salt spray corrosion and the salt spray corrosion specimen both originated from the pits on the surface.The pits on the surface of the former were produced by the interaction of corrosion and stress,and the pits on the surface of the latter were produced by salt spray corrosion.The micro morphology of the crack propagation zone and the instantaneous fracture zone were similar.The influence of salt spray corrosion on corrosion fatigue performance was mainly reflected in that the pits produced by salt spray corrosion reduce the crack initiation life of fatigue samples.