The use of low-temperature plasma in a combined technology for the formation of wear-resistant boron-containing coatings

A. A. Klopotov, Yu F. Ivanov, A. I. Potekaev, Yu A. Abzaev, M. P. Kalashnikov, A. V. Chumaevskii, O. G. Volokitin, A. D. Teresov, V. A. Vlasov, V. D. Klopotov

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Abstract

Combined technologies based on the use of concentrated energy fluxes, including low-temperature plasma and a pulsed electron beam, is currently considered to be an effective approach for surface modification of metals and alloys, cermet and ceramic materials. The purpose of the paper is to identify and analyze the patterns of changes in the elemental and phase composition, the state of the defective substructure, and mechanical properties of industrial steel Gr1J03502 subjected to combined treatment that includes plasma deposition of a powder coating based on the Ni-Cr-B-Si system and irradiation with an intense pulsed electron beam. The results obtained by optimizing the mode of the substrate surface fusion and the mode of powder deposition onto the molten surface of the substrate using low-temperature plasma generators of the original design are presented. It has been found that the optimum melting mode of the substrate surface is implemented with the following parameters of the plant: the feed rate is Vп = 50 … 150 mm/min, the distance is h1 = 30…100 mm, the scanning frequency is ω = 50 min−1, β = 75 … 90°, the amplitude is 90 … 100 mm, the plasmatron voltage is 160 V, the current strength is Im = 100 … 120 А. The optimal spraying conditions of the powders are as follows: h1 = 30÷50 mm; h2 = 100÷120 mm; β = 75÷90°; α = 45÷50°; ω = 50 min−1; Um = 140÷160 В; IS = 350÷400A; Im = 80÷100 A; GH (sprayed powder consumption) 0.8÷1 g/s. The characteristics of a plasma jet generated by an electric arc plasmatron are presented. The parameters of the electron beam are as follows: the energy of accelerated electrons is 18 keV, the energy density of the electron beam is 20 J/cm2 and 40 J/cm2, the pulse duration of the electron beam is 200 μs, the pulse repetition rate is 0.3 s−1, and the number of pulses is 10. It has been shown that plasma spraying of a powder coating leads to formation of a high relief surface containing micro and macropores, microcracks, and particles of the sprayed powder. Subsequent treatment of the modified surface with an intense pulsed electron beam of a submillisecond duration in the melting mode of the surface layer is accompanied by smoothing of the coating surface, saturation of the crystalline lattice of the steel surface with Ni, Cr, B, and Si atoms, formation of submicron-sized dendritic crystallization cells, precipitation of nanosized particles of the second phase, and formation of a quenching (martensitic) steel structure. Together, these transformations of the structure and phase composition of the material have led to a multiple increase in the microhardness of the surface layer with a thickness of up to 1500 mm.

Original languageEnglish
Article number125576
JournalSurface and Coatings Technology
Volume389
DOIs
Publication statusPublished - 15 May 2020

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Keywords

  • Electron beam
  • Microhardness
  • Phase composition
  • Plasma
  • Surface hardening

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry

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