Examples of corrosion cracking in Cr18Ni10Ti steel caused by residual stresses at bends and pittings

Resumo

The paper considers test results for corrosion cracking in unfixed U-shaped samples of steels Cr18Ni10 and Cr18Ni8 in a 1 N HCl solution at a room temperature and in a saturated NH₄Cl solution at 100°C. It is found that, in such samples, corrosion cracks occur on both the convex and the concave side. This fact contradicts theoretical concepts according to which residual stresses of opposite signs have to occur in the surface layers on opposite sides of the samples after the bending and subsequent elastic unloading. Examples are presented for the formation of CC microcracks near the growing pittings in smooth flat samples made of steel Cr18Ni10Ti in the absence of external stresses.