Composition and morphology of oxide films formed on PT-7M titanium alloy in high temperature water

The structure of the oxide film on PT-7M titanium alloy used in the construction of the first circuit of Russian small nuclear power plants (SNPP) is considered.The experiment was carried out in stainless-steel autoclaves with PPL liners at a temperature of 240°C.Deoxygenated water and solutions containing salts of metals that are components of stainless steel were used as the aqueous phases.Samples of titanium alloy after heating in autoclaves were examined by highresolution X-ray diffraction and X-ray fluorescence analysis and by scanning electron microscopy.According to the results of the study, the oxide film consists of a crystalline modification of titanium dioxideanataseand includes two layers: a dense one consisting of neat titanium dioxide and a loose one, which may include corrosion products of steel.A film with a thickness of about 100-120 nm is formed after 24 hours of the experiment and reduces the rate of titanium influx into the aqueous phase.After 336 hours (14 days) of heating, the thickness of the solid film is about 200 nm, while the sizes of the crystallites that make up the loose layer are 0.5-4 μm.