Hardening of cutting tools by combined gas nitriding method

Abstract In order to improve the strength properties of cutting tools made of high-speed steels, the article presents the results of a study of the possibility of using a combined method of surface hardening, which consists in nitriding in an ammonia medium at the first stage and oxidizing the nitrided layer in water vapor at the second stage. The formation of a thin dense oxide film consisting of a single magnetite and a dense nitride layer under it as well as a zone of internal nitriding following it are studied on the surface to be strengthened. It is established that the combination of the process in the first stage by zaevtektoidnoj temperature for the system “Fe-N” the temperature intervals of martensite transformation of residual austenite and the second step by zaevtektoidnoj temperature for the system “Fe-O” according to temperature intervals and tempering after hardening allows you to get the diffusion nitride-oxide layer with the desired structures and properties on the surface of high-speed steel.

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