International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

Researched were the physico-chemical properties, hardening and corrosion resistance of Cr₁₈Ni₁₀N type austenitic chromium- nickel stainless steels of different purity by the impurities and with different nitrogen content: from impurity level to 0.220%. It is demonstrated that nitrogen alloying is beneficial both for hardening and improvement of corrosion resistance of steel under conditions when nitrogen has the form of solid solution. Addition of 0.186-0.220% of nitrogen doesn’t reduce intercrystalline corrosion in standard environment of 0.5M H₂SO₄ + 0.01M KSCN and improves resistance to general and pitting corrosion in chloride-containing environments.

Pure nitric steel shows higher resistance to intercrystalline, general and pitting corrosion in chloride solutions than normal purity steel.

The hardening and austenite stability as a result of nitrogen alloying steel type of Cr₁₈Ni₁₀ in the temperature range, which is usual for the application of such steels as corrosion-resistant structural heat-resistant and/or cryogenic ones was studied. It is shown that the nitrogen alloying is perspective for strengthening and increasing of stability of austenitic stainless steels. Additional strengthening due to the preliminary cold or warm deformation hardening increases a tendency to the martensite formation under load, which limits the operating temperature of these steels. High-strength non-magnetic nitrogen-alloyed steels on the base of Cr₁₈Ni₁₀ steels containing up to 0.22 % of nitrogen are suitable for cryogenic application of non-deformed articles only. Otherwise, a strain-induced martensite will always form in them at temperatures below -70 °С. High strength, ductility and toughness of these steels can be achieved simultaneously only as a result of the TRIP-effect or fine-grained structure formation.

Warm and hot compressive tests, bending test, measurement of density, heat capacity and thermal conductivityw ere applied to study of feature mechanical and physical properties of cast alloys Fe + (16,8 – 25,6) % Mn + (0 – 14,4) % Al + (0,02 – 2,18) % C + (0,001 – 0,135) % N.

Estimates and experimental study of aluminum, carbon and nitrogen content effect for thermally and mechanically stable austenitic alloys based on Fe-(20–25)%Mn-(5–10)%Al-(0–10)%Ni-C-N, and hardening efficiency of these alloys by nitrogen addition are conducted. It is shown that the alloys based on the investigated system with C content of >1.2% for nickel-free system and ≥1.4 % for 5% and 10% of Ni can be proposed as high-strength non-magnetic cryogenic both in heat-treated and aged states. Nitrogen addition in the alloy containing 5% Al can be considered as micro-alloying, enhances dispersion of the cast structure. Ni enhances the dispersion hardening effect due to increase in carbide release rate resulted from the reduction of C solubility in austenite. Rational content of nickel equals to ~5%.