Experimental determination and calculation of wear resistance coefficient for coatings with added nanodispersed carbide particles during laser deposition

Abstract

The paper presents the results of domestic and foreign studies on laser deposition of coatings using hardening carbide phases, as well as metallographic and tribological studies of coatings with Ni-Cr-B-Si alloy powders and with the addition of nanodispersed particles of titanium and tungsten carbides. Wear resistance coefficients of coatings (K w ) were determined in Brinell-Haworth abrasive wear tests. The K w value was used in coating scratch tests to determine the coefficient С that depends on the coating hardness, treatment modes and addition of solid particles. It was found that the С value is influenced by a number of factors: processing speed, input laser power density, base penetration depth, carbide phase presence and content. The higher the penetration depth, the lower the coating wear resistance due to the mixing of the base material and the deposited coating. The introduction of tungsten carbide nanoparticles in the amount from 3 to 7 % increased the coating wear resistance by 1.5-2.0 times compared to the deposited PR-NiCr15BSi2 coating powder and by 4.6-7.1 times in relation to the base material - 40Cr steel. The microhardness of the initial powder coating was 6400-6600 MPa, and it increases with the introduction of carbides. For example, microhardness reaches 7620-9160 MPa at a WC content of 7 % in the coating. Positive deposition results were obtained at radiation energy density up to 50 W•s/mm 2 , but its further increase leads to the burnout of alloying elements and dissociation of carbides.