| 1. |
Hardenite has no acicular structure; it is often a mixture of martensite and austenite.
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| 2. |
The main reason for the formation of hardenite is the sharp concentration heterogeneity of austenite in terms of the carbon content, which occurs during heating (if the temperature is slightly above Ac1) and during cooling (if after austenitizing the steel is subjected to isothermal holding in the intercritical, pearlitic, or bainitic ranges for times exceeding the incubation period, in the process of which a substantial quantity of austenite is transformed).
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| 3. |
The formation of fine-grained austenite and the presence of inclusions (carbides, for example) also favor the formation of hardenite, since the boundaries of austenite grains and inclusions are barriers to the growth of the nuclei that are formed.
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Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 10, pp. 11–12, October, 1979.