Variation of the heat resistance of the KhN35VT alloy with the transformation conditions of the solid solution

Conclusions

1.The transformation conditions (different cooling conditions) of the solid solution in the austenitic precipitation-hardening alloy KhN35VT strongly affect the strength and plastic characteristics in short-term and long-term tension. 2.Isothermal treatment with single-stage tempering increases the long-term plasticity 150\2-300% by comparison with the standard treatment and also increases the creep resistance and long-term strength, which is most notable at low stresses.

In comparison with the same tempering after the standard treatment, two-stage tempering increases the plasticity and creep resistance by 200–300 and 200–500% respectively, while the long-term strenght remains at the same level or increases slightly. 3.After isothermal treatment with a low first tempering temperature (650\dgC) the impact strength after soaking at 650\dgC for 3500 h drops to approximately half its original value. With a high first tempering temperature (800\dgC) the impact strength decreases to a lesser extent-no lower than 6 kgm/cm². 4.It was confirmed that in double tempering of austenitic steels the first tempering temperature has a notable effect on the properties. The stability of the properties at working temperature depends on the proper conditions of the first tempering.