Possibilities of Using the Duplex System Plasma Nitriding + CrN Coating for Special Components

Abstract

The article deals with the replacement of hard chrome plating by applying the duplex system plasma nitriding + CrN coating (hereinafter referred to as PN + CrN). The goal of the research was to find a suitable alternative for steel surface treatment that would replace hard chrome plating and ensure similar mechanical and tribological properties. An exposed part of a small-bore weapon was selected for evaluation, namely the gas piston of the 42CrMo4 steel breech mechanism drive. The PN + CrN duplex system was compared with a hard chrome coating as well as a self-deposited CrN coating. The mentioned surface treatments were evaluated in terms of metallography, mechanical and tribological properties and surface texture. From the mechanical properties, the hardness of the surface was analyzed, an indentation test was performed (Mercedes test) and adhesive-cohesive behavior was evaluated (Scratch test). Furthermore, an instrumented penetration test was performed (an evaluation of plastic and elastic deformation work and indentation hardness). As part of the assessment of tribological properties, the Ball-on-Flat test, the measurement of the coefficient of friction and the measurement of traces of wear were performed. The surface texture was evaluated in terms of morphology and surface roughness measurement by selected 2D and 3D parameters. The PN + CrN duplex system showed higher hardness than hard chrome, better tribological properties (lower friction coefficient), but worse surface texture. The PN + CrN duplex system has proven to be a suitable alternative to the hard chrome coating for exposed parts of small-caliber weapons, which can be applied in arms production.

Modification of Diffusion Layers by Laser Shock Peening

“…Moreover, for a reason to further improvement of wear-resistance of the nitrided surfaces it is also possible to combine it with PVD coatings, as it is described in literature e.g. [16].…”

Cathodic arc deposition of metal-rich Cr-based coatings

“…Because of the dangers involved in using CrO3, it is important to find replacement processes capable of producing equally well performing coatings in a more sustainable fashion. The search for alternatives has been underway for at least 25 years with for example high velocity oxy-fuel spraying (HVOF), chemical vapor deposition (CVD), physical vapor deposition (PVD), other kinds of plating techniques, and plasma nitriding considered as possible options [15][16][17][20][21][22][23][24].…”