مقايسه رفتار خوردگي تنشي در فولادهاي زنگ نزن مارتنزيتي 420 و آستنيتي كم كربن 316

Comparison Between SCC Behavior of 420 Martensitic and 316L Low Carbon Austenitic Stainless Steels

Behaviors of stress corrosion cracking (SCC)in martensitic stainless steel(AISI 420) and low carbon austenitic stainless steel (AISI 316L) have been compared under different conditions of temperature, environment (MgCI2), and strain rate. The results show that decreasing strain rate has detrimental effect on mechanical properties of both steels, including their strength and ductility. Fractography of samples reveals that crack progresses by joining of dimples in fracture surface in all samples of AISI 420 steel, except in the sample that tested at 1.1 x 10-6s-1 strain rate, wherein intergranular fracture has also been observed on fracture surface. Necking phenomenon is only observed in air-tested samples of AISI 316L steel, but the other ones show lower ductility. AISI 316L samples, which tested under MgC12 environment, show a mixed fracture surface of intergranular and transgranular. Percent of transgranular fracture increases as strain rate decreases.