There have been investigated structure, phase composition and properties of carburized layers in steels 20Kh, 20KhN3A and 20KhN3A obtained by different variants of carburizing (3 variants: solid carburizing, gas and carburizing fluidized bed). Some aspects of retained austenite formation in gradient layers of widely applied carburizing steels are analyzed and specified in greater detail with the help of layer-by-layer X-ray analysis. There have been defined such parameters of retained austenite as distribution in carburized layer depth, concentration of carbon, stress condition. Extreme distribution of retained austenite in surface layer after carburizing and following standard heat treatment of the steels has been shown. Great quantity of retained austenite in carburized layers after final heat treatment (about 50 % of retained austenite in extreme point) does not lead to sudden decrease of microhardness in layer depth. Microhardness is distributed in layer depth intimately, without jumps after all variants of carburizing. There have been shown some difference between the definition of quantity of retained austenite by standard carburized layer structure scale and by layer-to-layer X-ray Diffraction analysis.

carburizing, retained austenite, carburizing layer, low-carbon carburizing steels, thermochemical treatment, layer-by-layer X-ray analysis, case-hardening, structure.