РЕГУЛИРУЕМАЯ ТЕХНОЛОГИЯ НИТРООКСИДИРОВАНИЯ НИЗКОЛЕГИРОВАННОЙ СТАЛИ

Abstract

In the article receiving surface, the diffusion nitride-oxide layer on low-alloy structural steel with specified structures and properties.
It is established that changing the composition and structure nitrid-oxid layer depends on many factors such as the saturation temperature, the activity of a saturating atmosphere and modes of nitriding in the ammonia at the first stage of processing and oxidation in water steam at the second stage of processing. In the process of nitrooxidathion first is the process of nitriding with the formation of the nitride layer, the nitride layer and formation of zones of internal nitriding in pure iron occurs according to the diagram "Fe-N".
When oxidation of nitride layer begins partial dinitriding on the surface to form a thin surface oxide layer after reaching certain thickness prevents dinitriding and makes the diffusion of nitrogen in the depth of the metal. As a result the oxidation increases the thickness of low-nitride layer and the zone of internal nitriding. For the development of regulated technology nitrooxidathion low-alloy carbon steels we have investigated the dependence of the composition and structure of nitride and oxide layer on the chemical composition of steel and technological parameters of the process. As a model alloy used in the iron and processed samples from industrial steel 40X, P6M5 and steel 45.
Investigated the saturation temperature in the range above and below the eutectoid temperature for the system "Fe-N", and "Fe-O" and found that the best structure is at temperatures below the eutectoid saturation. The change of phase composition of diffusion layers were studied by x- ray diffraction and auger spectral analysis obtaining nitrid-oxide layer at different treatment modes.
Investigated as structural steel 40X, samples of which are treated in an atmosphere of pure ammonia, at a degree of dissociation α=40...60%, at temperatures 6200С and 5800С without removing from the furnace was subjected to oxidation in water vapor and the addition of complexion.
Microsections on the treated samples determined the distribution of elements over the depth of the oxide and nitride layers of Auger-spectral analysis. The study found education, nitride layer, carbonitride character, which is due to the fact that the nitriding is dicarbonizithion, nitrogen replacing carbon in the steel matrix and carbon in the matrix is involved in the formation of the layer.
Determined the formation of the surface layer oxycarbonitrid nature that when oxidation due to diffusion of oxygen occurs at the same time dinitriding and dicarbonizithion in part of the nitride zone. The results of obtaining the adjustable structure of nitride and oxide layer by choosing the saturation temperature change of the nitrogen potential. When oxidation of nitride layer, is formed on the surface of a dense oxide layer that prevents dicarbonizithion developed and obtained nitride layer and simultaneous diffusion of nitrogen from the nitride zone into the sample with the formation of the lower nitride zone and oxygen gas from the atmosphere. The study regimes for the technological process of a combined technology of nitrooxidathion with getting adjustable thick carbonitride, oxycarbonitride layers that has the best physico–mechanical and physico-chemical properties than the nitride layer.