FORMATION OF MULTILAYER COATINGS BY ELECTROSPARK ALLOYING

Abstract

The problem of increasing the reliability and service life of dynamic equipment parts operating at high speeds, loads, and temperatures, in corrosive, abrasive, and other environments, is considered. The relevance of increasing the thickness of the high-hardness zone for parts of friction pairs with abrasive and other types of wear is noted. The research results and the development of a method for protecting steel products against wear by applying a quasimultilayer wear-resistant coating (QWC) onto the wear surface by electrospark alloying (ESA) and increasing the thickness of the high-hardness layer are described. Based on metallography, hardness measurement, electron microprobe analysis, and X-ray diffraction, the regularities of forming the QWC by ESD with alternating alloying electrodes at sequential deposition of carbon, aluminum, and T15K6 hardmetal alloys onto a 12Kh18N10T steel substrate are established. The coatings deposited in this sequence have the greatest high-hardness zone (320–360 μm) and the smallest surface roughness (7.5 μm). The formation of TiC carbides, intermetallic compounds, and a disordered solid solution with a bcc crystal lattice promote the maximum microhardness of the surface layer (about 11500 MPa). In this case, the diffusion zones of carbon and tungsten are increased. Electrospark deposition according to the described technology allows increasing the hardness and thickness of the strengthened layer. The studies show that high hardness and thickness of the high-hardness layer cannot be achieved with alternating alloying electrodes by successive deposition of carbon and T15K6 layers (without an aluminum sublayer) on a 12Kh18N10T steel substrate.