显微组织对25CrMo48V超高强度钢在NaCl溶液中腐蚀行为的影响

采用动电位极化法和电化学阻抗法等研究了不同冷却方式对25CrMo48V超高强度钢在NaCl溶液中的腐蚀行为的影响。结果表明,25CrMo48V超高强度钢炉冷后的显微组织为多边形铁素体和珠光体,空冷后为下贝氏体和多边形铁素体,水淬后为板条马氏体。由电化学分析可知,不同显微组织的试样在NaCl溶液中具有相似的电化学腐蚀过程;在质量分数为1%、3%、5%、7%的NaCl溶液中,不同显微组织的试样具有相同的腐蚀速率变化规律,下贝氏体组织的空冷试样腐蚀速率最低,而板条马氏体组织的水淬试样腐蚀速率最高。通过观察不同显微组织的试样在NaCl溶液中浸泡后的宏观腐蚀形貌,可知下贝氏体组织的耐腐蚀性最好,板条马氏体组织的耐腐蚀性最差,与电化学测试结果一致。

Effect of microstructure on corrosion behavior of 25CrMo48V ultra-high strength steel in NaCl solution

The effects of different cooling methods on corrosion behavior of 25 CrMo48 V ultra-high strength steel in NaCl solution were studied by potentiodynamic polarization method and electrochemical impedance method.The results show that the microstructure of the 25 CrMo48 V ultra-high strength steel after furnace cooling is polyhedral ferrite and pearlite,the microstructure is lower bainite and polyhedral ferrite after air cooling,and the microstructure is lath martensite after water quenching.The electrochemical analysis shows that the samples with different microstructure have similar electrochemical corrosion process in NaCl solution,and in the NaCl solution with mass fraction of 1%,3%and 5%,the corrosion rate of the samples with different microstructure has the same law,the corrosion rate of air-cooled sample with lower bainite structure is the lowest,while that of quench-cooled sample with lath martensite structure is the highest.By observing the macroscopic corrosion morphology of the samples with different microstructure immersed in NaCl solution,it can be seen that the corrosion resistance of the steel with lower bainite structure is the best,and the corrosion resistance of the steel with lath martensite structure is the worst,which is agreement with the electrochemical test results.