Development of the hardness of the nitrided case
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Direct measurements of the hardness in the process of nitriding and during subsequent cooling showed that the hardness of the nitrided case develops primarily during cooling after completion of the nitriding process.
The high hardness of the nitrided case on steels alloyed with nitride-forming elements (Al, Mo) is the result of the overall hardening effect of: a) formation of nitrides of alloying elements in the process of nitriding (the hardening effect of these nitrides is negligible); b) precipitation and preprecipitation of dispersed nitrides of alloying elements in the process of the intermediate γ→α transformation; c) precipitation or preprecipitation of nitrides of alloying elements due to the lower solubility at decreasing temperatures.
The study of the development of the hardness of the nitrided case on alloys containing aluminum and molybdenum leads to the conclusion that the most effective mechanism of hardening is the precipitation or preprecipitation of dispersed nitrides of alloying elements in the process of the intermediate γ→α transformation.
KeywordsPrecipitation Aluminum Molybdenum Nitrides Direct Measurement
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