Long-Term Annealing Resistance of Ferritic Chromium Steels Subjected to High-Temperature Nitriding

Abstract

The influence of long-term annealing (at 700°C, 30 h) on the structure and mechanical properties of ferritic chromium steels 08Kh17T and 15Kh25T has been comparatively studied after high-temperature nitriding and heat treatment (annealing). Both steels in all considered states are characterized by high resistance against oxidation during long-term annealing. Long-term annealing of the steels in the initial non-nitrided state and after nitriding and intermediate annealing at 700°C leads to a decrease in the ultimate tensile strength and yield strength by 10–15%. The maximum decrease in the strength (by 1.2–1.7 times) upon long-term annealing is observed in both steels after preliminary nitriding and annealing at 550°C due to partial coagulation of the nitride phase.