Increasing the Wear Resistance of Structural Steel Parts by Ion Nitriding during Complex Surface Preparation Using the Dry Electropolishing Method

Abstract

The article considers the results of studies on the wear resistance of machine parts made of structural steels with nitrided layers obtained during complex surface preparation before ion implantation and subsequent ion nitriding. Nitrided layers on parts made of structural steels produced using traditional technology are not able to fully realize their potential for wear resistance, since oversaturation of grain boundaries with nitrogen leads to a decrease in the strength of their boundaries, the formation of a nitride grid and to the staining of grains and their fragments during wear friction. The method developed by the authors for activating the surface layer of parts by high-energy ion implantation treatment, in some cases, eliminates the process of nitride mesh formation. However, the microgeometric and physicomechanical heterogeneity of the nitrided surface, as well as the presence of impurities on the surface, reduces the operational properties of the nitrided layer. It is shown that the use of dry electropolishing makes it possible to achieve the lowest surface roughness compared to other polishing methods, while ensuring the most homogeneous state of the surface layer material. It is also shown that the use of electroadsorption for surface cleaning makes it possible to eliminate impurities present on the surface of parts, which contributes to the most effective use of subsequent activation of the surface layer by high-energy ion implantation. It is also shown that as a result of the application of complex surface preparation of the part, it is possible to fully realize the possibilities of ion nitriding technology. Using the example of rotors of screw pumps operating under conditions of intense wear friction, the results of comparative wear tests are presented. It is shown that the use of complex surface preparation, including dry electropolishing and electroadsorption before activation of the surface layer by high-energy ion implantation increases the wear resistance of the nitrided layer by about 2 times.