Electric Arc Spraying of Composite Metal-Polymer Coatings
Keywords
Abstract
A method for forming composite electric arc coatings by using a modernized EM-14M spraying gun with a powder feed unit of free powder to a high-temperature heterophase jet during spraying is proposed. Samples of a metal-polymer composite coating of the composition steel Sv-08-G2S-O — polymer P-EP-219 were obtained. Experimentally established the necessary zone for the supply of polymer powder was to prevent its destruction in the high-temperature zone of the arc discharge and the optimal modes of deposition metal-polymer coatings: current 90…100 A, arc voltage 25 V, compressed air pressure 0,4…0,6 MPa, polymer powder consumption 25 g/min, spraying distance 100...120 mm. If these modes are observed, the conditions for the formation of a high-quality metal-polymer coating with a thickness of 0.5-0.8 mm with a maximum content of the polymer component of 40 %(vol.) are provided. A scanning electron microscope REMMA-102-02 was used to investigate the microstructure of the sprayed coatings. It has been established that the porosity of composite coatings is reduced from 13 % to 7 % in comparison with convention steel coatings. The phases were identified by determining their microhardness on cross sections with a load on the indenter of 50 g. It was found that the microhardness of the metal matrix is 1716 MPa; polymer component — 128 MPa. It is shown that the deposited coatings are characterized by the presence on their surface of a continuous polymer film with a thickness of 10 to 100 μm, which is formed as a result of the fact that the polymer solidifies later than the crystallization of metal particles. It has been experimentally confirmed that the thermal conductivity of metal-polymer coatings deposited from the SV-08G2S-O – P-EP-219 composition decreases by 46 % in comparison with the thermal conductivity of convention coatings from SV-08G2S-O wire. The proposed coatings are recommended to be used as anticorrosion and heat-insulating coatings on various structures due to the thin surface polymer film and low thermal conductivity.
