新型超高强度钢Cr12Ni4Mo2Co14在酸性环境中的应力腐蚀行为

STRESS CORROSION CRACKING BEHAVIOR OF A NEW KIND OF ULTRAHIGH STRENGTH STEEL Cr12Ni4Mo2Co14 IN ACID ENVIRONMENT

采用慢应变速率拉伸实验研究了一种新型超高强度钢在酸性环境中Cl^-和H对应力腐蚀行为的交互作用,并采用SEM观察了试样断口形貌.结果表明,Cl^-显著提高Cr12Ni4Mo2Co14钢的应力腐蚀敏感性,实验条件下临界Cl^-浓度[Cl^-]c为0.15%左右.当Cl^-浓度高于[Cl^-]c时,Cl^-引发严重的点蚀,应力腐蚀裂纹起源于点蚀坑处.Cr12Ni4Mo2Co14钢在含Cl^-溶液中的断裂机理可以用"滑移-膜破裂"机制进行解释.充氢后的Cr12Ni4Mo2Co14钢发生氢致开裂,断口上出现二次裂纹.临界充氢电流密度i_([H]c)为10 m A/cm^2(溶液p H=5,充氢时间为30 min).当充氢电流密度大于i_([H]c)时,Cr12Ni4Mo2Co14的强度损失和塑性损失趋于最大值.溶液中的Cl^-浓度和材料中的H有复杂的交互作用,并非简单的加和作用.

In recent years, the development of aerospace industry puts forward a higher requirement for the high strength, high toughness and good weldability of steel materials. Cr1 2Ni4Mo2Co 14 steel is a new kind of ultrahigh strength steel, which is usually used as structure materials under complex stress/strain conditions. In this work, the stress corrosion cracking behavior of Cr12Ni4Mo2Co14 steel in acid environment was studied by slowstrain rate test （SSRT） and SEM. The results showed that the stress corrosion cracking （SCC） susceptibility of Cr12Ni4Mo2Co14 steel was enhanced by chlorine ions remarkably. The critical value of chlorine ion concentration was about 0.15%, above which, severe SCC occurred induced by chlorine ions, and the SCC cracks started from pits. The SCC mechanism of Cr12Ni4Mo2Co14 steel in acid solution containing chlorine ions can be clarified by ＂slide-film breaking＂ model. The hydrogen-charged samples of Cr12Ni4Mo2Co14 steel were sensitive to hydrogen induced cracking, and second cracks occurred on the fracture surface. The critical value of hydrogen-charged current density is 10 mA/cm2 for 30 min in solutions with pH=5, above which, the losses of strength and plasticity of Cr12Ni4Mo2Co14 steel reached to the maximum. The effects of chlorine ions and hydrogen had a complex in- teraction which cannot be added up directly.