Effect of annealing steel 18%Cr10%NiTi at temperatures between 550 and 850 degC on character of corrosion damage in oxidation media

The effect was studied of annealing on the nature of corrosion damage of austenitic stainless steel type 08Cr18Ni10Ti in an oxidation medium with the aim of clarifying the views on precipitation processes taking place within the tempeature range 550 to 850 degC. It was found that a time interval exists for each temperature in the said range when corrosion rate in boiling 65% HNO3 increases, which is associated with intergranular corrosion damage. It was shown that intergranular corrosion of nonsusceptibilized specimens was initiated by the dissolution of TiC discontinuously extracted on grain boundaries. The application of three-stage annealing in a temperature range of 680 to 800 degC significantly reduced the corrosion rate when compared to the effect of single-stage annealing under comparable conditions. The combination of temperatures used obviously affected both the precipitation kinetics and the chemism of the precipitating phases. (Z.M.)