Formation of functional protective chromium-based coatings by friction cladding

Abstract

Corrosion damage to metal parts and structures is one of the most important scientific, technical and economic problems. Coatings based on chromium are widely used in modern mechanical engineering. They are used both to solve problems related to the restoration of the size and shape of the surfaces of worn parts, and to improve performance, for example, wear and corrosion resistance, heat resistance, reflective and protective and decorative ability, etc. One of the promising methods for the formation of anti-corrosion coatings is the technology of friction cladding using a flexible tool - a rotating wire metal brush. The article studies coatings formed by friction cladding from donor materials (sintered composites) containing powders of chromium (about 80 %), zinc, copper, tungsten carbide, tungsten-cobalt, hexagonal boron nitride, thermally expanded graphite. The chemical composition of donor materials and the resulting coatings was studied by X-ray diffraction analysis. It was determined that the composition of the obtained coatings based on chromium correlates with the composition of donor materials, however, it additionally contains elements of nickel and iron. It is assumed that iron in the composition of the coating appears as a result of cutting off the particles of the steel base by the bristles of the brush and transferring them to the forming layer of the coating. The nickel content indicates that particles of the wire bristle material of the brush are also introduced into the coating layer. Corrosion tests were carried out in a salt fog chamber KST-2 according to GOST 9.308-85 of samples with coatings obtained by galvanic chromium plating and friction cladding. The coated samples were kept in the chamber for 192 hours. The galvanized coating withstood the test without any signs of corrosion. Traces of corrosion appeared on friction clad coatings, while on all samples the corrosion area was no more than 7 %. It is conditionally accepted that coatings obtained by friction cladding have satisfactory corrosion resistance. The results of X-ray fluorescence analysis of the chemical composition of donor materials and coatings were obtained with the financial support of the Ministry of Science and Higher Education of the Russian Federation (Project No. FZRU-2020-0011). The results of tests for corrosion resistance of samples with applied coatings were obtained with the financial support of the Belarusian Republican Foundation for Basic Research (grant T21ET-005).