Structure and properties of high-strength stainless steel 1Kh15N4AM3

Conclusions

• 1. Tempering of steel 1Kh15N4AM3 at 200° leads to high mechanical properties: σ_b ≈ 160 kg/mm²,δ₅ ∼ 16%, ψ ∼ 60%, a_n=15 kg-m/cm², a_f.cr.=7 kg-m/cm².

  The high strength results from the high dislocation density, the presence of twins, and also from the fairly large amount of carbon and nitrogen (total ∼0.23%) retained in the solid solution. The high ductility is due to the presence of 15–20% evenly distributed austenite.

• 2. Tempering at 300−350° results in some lowering of the strength (σ_b ∼ 145 kg/mm²) and increase of the plasticity and ductility. The change in the properties is due to the smaller amount of carbon and nitrogen in the solid solution, while the high dislocation density and substantial second-order distortion are retained. With decreasing numbers of interstitial atoms in the solid solution no precipitates are formed.

• 3. The secondary hardening in tempering at 450−500° concludes with the formation of highly dispersed M₂X (detected after overaging), the strength reaching \t}155 kg/mm² with some decrease of the fracture toughness and substantial reduction of the work of crack propagation. The structure is characterized by some reduction of the dislocation density and considerably smaller second-order distortion.

• 4. Raising the temperature to 650−700° lowers the strength, since M₂₃C₆ forms in the grains and grain boundaries.

• 5. The reverse α→γ transformation begins at 575−600° and the largest amount of stable austenite is formed after heating at 625−650° for 1−2 h.