Surface Modification of Economically Alloyed Steel 9XC in Nitrogen-Carbon Medium in Order to Increase Wear Resistance

Purpose. The study of nitrocementation of steel 9XC at a temperature of 560 ° C in a highly active solid nitrogencarbon medium based on amorphous carbon and nitrogen–containing components – carbamide and potassium ferricyanide – was undertaken.

Methods. The microstructure of nitrocemented steel on transverse sections was studied using an XIMEA optical microscope with Axalit software, as well as using a Qanta FEG – 650 electron scanning microscope with a focused ion beam EBCD microanalysis system. A layer–by-layer X-ray diffraction analysis of samples on the XR-700S diffractometer in chrome radiation was carried out.

Results. The wear tests of carbonitrated specimens were carried out under friction conditions similar to those of punching tools. The wear resistance of nitrocarburized samples was studied on an SMTs-2 friction machine. The tests were carried out both under dry friction conditions and under boundary friction conditions. High efficiency of the proposed paste at this temperature was experimentally shown. As a result of nitrocementation, modified layers saturated with solid inclusions (ε-phases) are formed on the surface of steel. These modified layers are characterized by high hardness, low coefficient of friction and high wear resistance.

Conclusion. Based on the results of the studies, it can be concluded that the nitrocarburizing of die steel 9XC, carried out in a highly active nitrogen-carbon paste at a carbonitration temperature (560 ° C), contributes to the formation of modified layers saturated with carbonitrides (mainly hexagonal carbonitride ε) on the surface. The modified layers are characterized by a very low coefficient of friction and very high wear resistance. Nitrocarburized steel 9XC can be used for the manufacture of working parts of dies, instead of more expensive high-alloy steels (for example, X12), which can increase the economic efficiency of mechanical engineering.

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