Annealing effect on structure, phase composition and mechanical properties of high-nitrogen austenitic steel

Abstract

The paper presents transmission and scanning electron microscopy investigations of the microstructure, dispersed particle precipitation and mechanical properties of the high-nitrogen austenitic steel VNS-53-Sh after 700 °C annealing for 10 h. It is shown that dispersed particles of Cr₂N chromium nitrides and M₂₃C₆ carbides precipitate after annealing. The volume fraction of each particle type does not exceed 1%. Nitrides precipitate near the grain boundaries via discontinuous precipitation of austenite with the cell formation. Carbides precipitate at the grain boundaries and incoherent twin boundaries coherently with the austenite matrix. The dislocation density decreases by about an order of magnitude relative to the quenched state. Yield and tensile strength decrease respectively by ≈1.2 and ≈1.1 times relative to the initial state. Elongation to fracture increases by 1.6 times. It is found that the dislocation substructure recovery and precipitation of dispersed particles affect strength and plastic properties of the VNS-53-Sh.