Eigh-temperature brittleness and selection of quenching temperature for stainless maraging steels

Conclusions

• 1. High-temperature brittleness due to slow cooling in the range of 800–1000°C is caused by the precipitation of titanium carbides in the boundaries of austenite grains.

• 2. Rapid cooling from the hot deformation temperature or the completion of deformation at a temperature not over 800–850° prevents high-temperature brittleness.

• 3. The hot rolled steel has the optimal combination of properties after hardening. Additional heating for quenching may lower the strength (the effect of HTTMT is eliminated) and the toughness (χ phase is precipitated).

• 4. The quantity of intermetallic compounds in anodic residues (χ phases, Fe₂Mo and ε-Fe₃Mo₂) after holding at 700–900° for 1 h may reach 2.5%; the type of intermetallic compounds and the quantitative ratio evidently depend on the temperature of the preceding treatment and the quenching temperature. With quenching from 950° and higher the phase composition is qualitatively and quantitatively similar to that of the hot worked steel.

• 5. In cases where the hot worked must be reheated the optimal quenching temperature is 950–1000° with holding for 1 h or more, followed by rapid cooling.