High-strength low-alloy steels used for oil and gas pipelines are vulnerable to intergranular stress corrosion cracking in moderately alkaline soils. The mechanism of corrosion-induced embrittlement under such conditions is not yet understood. Nanoindentation was used to detect localized degradation of mechanical properties near internal grain boundaries of X-70 steel undergoing intergranular corrosion at active dissolution potentials at pH 8.2. The measurements identified a one-micron thick mechanically-degraded layer with 25% reduced hardness near corroded grain boundaries. It is suggested that the corrosion process may introduce an active softening agent, possibly non-equilibrium lattice vacancies generated by oxidation.

石油和天然气管道中使用的高强度低合金钢在中度碱性土壤中极易发生晶间应力腐蚀开裂。在这种条件下腐蚀引起的脆化的机理尚不清楚。纳米压痕用于检测在pH 8.2的主动溶解电位下经受晶间腐蚀的X-70钢内部晶界附近的机械性能的局部退化。测量结果确定了一个1微米厚的机械降解层，在腐蚀的晶界附近硬度降低了25％。建议腐蚀过程可能引入活性软化剂，可能是由于氧化而产生的非平衡晶格空位。