Nanocrystalline Structure Produced by Complex Surface Treatments: Plasma Electrolytic Nitrocarburizing, Boronitriding, Borocarburizing, and Borocarbonitriding

Abstract

In present study, the feasibility of improving tribological performance of low carbon chromium steel by applying complex surface treatments which combines the method of Plasma electrolytic saturation (PES) is investigated. The different regimes of diffusion treatments on the surface affect the mechanical and tribological characteristics of the steel substrates by production of nanocrystalline interlayers. The major advantage of the PES technique was shown to be the extremely high nanocrystalline coating growth rate by the aggressive ionized particles. The combination of characteristics far exceeds the capabilities of the diffusion procedure by means of PES technique. It was found that the different compositions of interlayers produced by means of complex diffusion treatments eliminate the sharp slope of the microhardness profile. The gradual decrease of microhardness with distance from the surface, provides a good tribological performance. The boride layer reveals the highest value of microhardness among the produced interlayers. In the case of tribological performance, the boronitrided sample shows the best characteristics which are related to the formation of nanocrystalline nitride layer beneath the top boride layer.