Conclusions
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1.
After austenization at 1150°C and quenching in oil, precipitation of clusters enriched in Cr and C occurs in the austenite of high-chromium ledeburitic steel. With tempering temperature increasing up to 300°C the number of clusters increases, and at the same time they start to transform into alloyed cementite (Cr, Fe)3C. The transformation proceeds at temperatures above 400°C. At that time the cementite particles grow and their number decreases. During a single tempering at 520°C, the particles become almost-completely dissolved in the austenite.
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2.
The processes of particle precipitation in austenite influence its mechanical properties. Increasing the number of particles in austenite at tempering temperatures up to 300°C increases the microhardness and the fracture toughness. Fracture toughness decreases with increase of size and distance between the particles.
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3.
Variation of the number of clusters and cementite particles with tempering temperature is the main reason for the thermal stability of residual austenite in the steel studied. Cementite instability, and its dissolution in austenite at 520°C, causes the secondary transformation into martensite during the cooling process.
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People's Republic of Bulgaria. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 8, pp. 35–39, August, 1984.
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Tolev, N. Influence of precipitation processes on the mechanical properties and redidual austenite stability of high-chromium tool steel. Met Sci Heat Treat 26, 608–612 (1984). https://doi.org/10.1007/BF00707801
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DOI: https://doi.org/10.1007/BF00707801