Effect of the Conditions of the Nanostructuring Frictional Treatment Process on the Structural and Phase States and the Strengthening of Metastable Austenitic Steel

Resumo

The effect of the multiplicity of frictional loading with a sliding synthetic diamond indenter at room temperature in an argon medium and the temperature of loading in the range of −196 to +250°C on the phase composition, fine structure, and micromechanical properties of the surface layer of metastable austenitic chromium-nickel steel has been studied. It has been established that the completeness of the strain-induced martensitic γ → α′ transformation in the surface layer of steel is determined by the loading multiplicity and temperature, as well as the level of strengthening grows with an increase in the frictional loading multiplicity, but weakly depends on the frictional treatment temperature. According to the microindentation data, the characteristics of the surface layer strength and resistance to elastic and plastic deformation are improved with an increase in the frictional loading multiplicity. Frictional treatment by scanning with a synthetic diamond indenter at room and negative temperatures provides high quality for the treated surface with a low roughness parameter (Ra = 80.115 nm), and an increase in the frictional loading temperature to 150–250°C leads to the development of a seizure and growth in Ra to 195–255 nm. Using transmission electron microscopy (TEM), it has been shown that frictional treatment results in the formation of nanocrystalline and fragmented submicrocrystalline structures of strain-induced α′-martensite (at a loading temperature of −196°C) and austenite (at a loading temperature of +250°C) in the surface layer of steel alongside with two-phase martensitic-austenitic structures (at a loading temperature of +20°C).