The features of the structure and the mechanical and tribotechnical properties of an austenitic nitrogen steel (Cr16.5, Mn18.8, C0.07, N0.53, Si0.52 wt %, and Fe for balance) after frictional treatment have been studied. It has been shown that, along with twinning, the nitrogen austenite upon frictional treatment undergoes a γ → stacking fault → ε transformation. The strengthening of the steel by the frictional treatment manifests in a delay of the onset of the plastic flow. In the structure of the surface layer with a thickness of 5 μm, a high concentration of stacking faults has been detected. The mechanical properties depend on the orientation of the acting stresses relative to the direction of the frictional treatment. Upon the sliding friction of a ball made of hard alloy (94%WC + 6%Co) on the strengthened surface, an anomalously low coefficient of friction of 0.13 is observed. The coefficient of friction in the presence of abrasive particles in the form of wear debris increases to 0.50; however, the wear rate is almost two times lower compared to the same characteristic for a nonstrengthened surface of the nitrogen steel tested under the same conditions.

The paper presents the results of tensile and impact bending tests of 17%Cr-19%Mn-0.53%N high-nitrogen austenitic stainless steel in temperatures ranging from −196 to 20 °C. The steel microstructure and fracture surfaces were investigated using transmission and scanning electron microscopes, as well as X-ray diffraction analysis. The steel experiences a ductile-to-brittle transition (DBT); however, it possessed high tensile and impact strength characteristics, as well as the ductile fracture behavior at temperatures down to −114 °C. The correspondence between γ–ε microstructure and fracture surface morphologies was revealed after the tensile test at the temperature of −196 °C. In this case, the transgranular brittle and layered fracture surface was induced by ε-martensite formation. Under the impact bending test at −196 °C, the brittle intergranular fracture occurred at the elastic deflection stage without significant plastic strains, which preceded a failure due to the high internal stresses localized at the boundaries of the austenite grains. The stresses were induced by: (i) segregation of nitrogen atoms at the grain boundaries and in the near-boundary regions, (ii) quenching stresses, and (iii) reducing fcc lattice volume with the test temperature decrease and incorporation of nitrogen atoms into fcc austenite lattice. Anisotropy of residual stresses was revealed. This was manifested in the localization of elastic deformations of the fcc lattice and, consequently, the stress localization in -oriented grains; this is suggested to be the reason of brittle cleavage fracture.

The study investigates an electron beam cladded coating of nitrogen-alloyed austenitic steel (24.4Cr, 16.4Mn, 0.18Ni, 1.1Si, 0.57С, 0.7N, rest Fe (wt %)). Cladding was performed by a continuous low-energy (27 keV) and low-current (0.02–0.04 A) focused electron beam on an electron beam system at a residual pressure of 0.1 Pa. The microstructure, phase composition, and chemical composition of the coating were examined by OM/AES/XRD/SEM/EDS methods. The coating has no pores and is characterized by high work hardening and wear resistance. The formation of М₇(С, N)₃ carbonitrides in the steel plays a crucial role in the control of the structure and wear resistance of the applied coating, because carbonitrides are able to distinguish between the lattice curvature zones and the stable translationally invariant lattice. Frictional loads arising during wear trigger a γ → α′ transformation. With increasing frictional load, the coefficient of friction decreases.

—The deformation behavior and structure of 16.5Cr–18.8Mn–0.53N–0.07C steel deformed by tension in the temperature range from –196 to + 20°С have been investigated. A stage with a constant strain-hardening rate has been shown to be present in the temperature range –65 < t ≤ 20°C, which at –65 < t < 0°C is periodically interrupted by the parabolic hardening stage. Multiple strain localization has been observed in the samples at test temperatures of –65 < t < 0°С. There is γ → ε-transformation in steel at all deformation temperatures. Its contribution to the total ductility of steel increases as the test temperature decreases. Tension tests of steel at –196°C has resulted in γ → ε → α' transformation at the strain localization stage.