Experimental and Computational Determination of the Wear Resistant Coefficient for Coatings with Nanodispersed Carbide Particles Added by Laser Surfacing

Abstract

The results of domestic and foreign investigations into the laser surfacing of coatings containing a strengthening carbide phase, as well as metallographic and tribological investigations of coatings by alloy powders of the Ni–Cr–B–Si system, including the addition of nanodispersed titanium and tungsten carbide particles, are presented. Values of the wear resistance coefficient (Kw) of coatings during abrasive wear testing according to the Brinell–Haworth scheme are determined. The use of Kw makes it possible to determine coefficient C when performing a scratch test of the coatings, which depends on the coating hardness, treatment modes, and addition of solid particles. It is found that the magnitude of C is affected by a series of factors such as the processing speed, input laser power density, base melting depth, and carbide phase presence and content. The larger the melting depth is, the lower the coating wear resistance is, which is associated with mixing the base material and surfaced coating. Introducing tungsten carbide nanoparticles in an amount from 3 to 7% makes it possible to increase the coating wear resistance by a factor of 1.5–2.0 when compared with the surfaced powder coating made of the PR-HKh15SR2 alloy and by a factor of 4.6–7.1 with respect to the base material—steel 40Kh. Microhardness of the initial powder is 6400–6600 MPa and increases with the introduction of carbides into it. For example, microhardness reaches 7620–9160 MPa with a WC content of 7% in the coating. Positive surfacing results are found with the emission power density up to 50 W s/mm2, but its further increase leads to the burnout of alloying elements and dissociation of carbides.