Improvement of the resistance to corrosion by superheated steam of Incoloy Alloy 800 tube material by surface deformation treatment

Samples of Incoloy 800 (%, 45.8 Fe, 31.7 Ni + Co, 20 Cr, small additions of Cu, Mn, Al, Ti, Si) were subjected to the action of superheated steam (500 and 1000 h, 600 and 620°C, 1, 70 and 145 atm, 0.03 and 3.5 m/s) after surface deformation - rolling, bending, sandblasting, needle peening, sanding. The measured weight loss was evaluated in relation to the surface condition. It was found that the corrosion losses are inversely proportional to the degree of deformation: corrosion is reduced by 95–96% at 90% deformation of the sample. In this regard, bending deformation, sandblasting, and needle peening are the most effective, while rolling or sanding only deforms a very thin surface layer, which then lacks self-healing properties. The composition of the corrosion products depends on the degree of deformation: increasing deformation leads to a decrease in iron content, while the contents of nickel, chromium, and manganese in the corrosion products increase. This phenomenon is causally related to the protective effect, which is based on the formation of chromium oxide layers.