Electrospark Deposition of Multilayer Coatings

Abstract

The paper examines how to increase the reliability and service life of dynamic equipment parts operating at high speeds, loads, and temperatures and in corrosive, abrasive, and other environments. Increase in the thickness of the high-hardness layer for friction parts subjected to abrasive and other types of wear is a relevant problem. The research findings and the method developed for protecting steel products against wear by applying a quasimultilayer wear-resistant coating (QWC) onto the wear surface by electrospark deposition (ESD) 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 producing the QWC with alternating alloying electrodes by sequential ESD of carbon, aluminum, and T15K6 hardmetal layers onto a 12Kh18N10T steel substrate are established. The coatings deposited in this sequence have the greatest high-hardness area (320–360 μm) and the smallest surface roughness (7.5 μm). The formation of TiC carbides, intermetallic compounds, and a disordered bcc solid solution promotes the maximum microhardness of the surface layer (approximately 11500 MPa). The diffusion zones of carbon and tungsten increase in the process. Electrospark deposition in accordance with the described technique allows the hardness and thickness of the strengthened layer to be increased. The experiments show that the hardness and thickness of the high-hardness layer cannot be increased only with alternating alloying electrodes by successive deposition of carbon and T15K6 layers (without an aluminum sublayer) on a 12Kh18N10T steel substrate.