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[References: 11 tit.]

Effect of age hardening regime (at the temperatures of 700 and 800°C for 10 min to 10 h) on phase composition and microhardness of high-nitrogen steels was investigated. Before age hardening treatments, specimens of V-free and V-alloyed steels, Fe-23Cr-17Mn-0.1C-0.6N (0V-HNS) and Fe-19Cr-22Mn-1.5V-0.3C-0.9N (1.5V-HNS), were water-quenched after 1200°C (for 0.5 h) to produce supersaturated solid solution of interstitial atoms (nitrogen and carbon) in austenite (7% ferrite in 0V-HNS, no ferrite and <5% VN precipitates in 1.5V-HNS were formed). V-alloying changes a kinetics of age-hardening in high-nitrogen steels. According to XRD data, aging at 700 and 800°C results in decomposition of austenite and ferrite in 0V-HNS and formation of duplex microstructure, which consist of high-nitrogen austenite, ferrite, Cr2(N, C) precipitates and intermetallic σ-phase. Such duplex microstructure consists of two types of grains: (1) austenitic grains with precipitates mainly along grain boundaries possess lower microhardness characteristics (about 3.5 GPa); and (2) decomposed multiphase grains have high microhardness (4.5-5.5 GPa depending on aging duration). After aging of vanadium-containing steel at 700 and 800°C, rather homogeneous composite structure forms, which consists of high-nitrogen austenite, ferrite and (V, Cr) (N, C) particles randomly distributed both on grain boundaries and in grain bodies. This stricture possesses high microhardness values about 4.0-4.5 GPa. Independently on age hardening regime and steel composition, the most pronounced effects of hardening occur during short-time age hardening regimes (0.5-1 h).