RU2219212C1 - Composition material for tribotechnical coatings - Google Patents

Abstract

FIELD: polymeric materials technology. SUBSTANCE: composition material based on polyamide matrix and carbon filling agent comprises as polyamide matrix the modified polyamide powder-like product of cryogenic grinding thermomechanically combined mixture of polyamide-6 and polyethylene taken in the ratio = 10:(1-0.1) and as carbon filling agent mixture of carbon components of graphite-like and diamond-like modification and carbon-graphite fiber taken in the ratio = (1:1:20)-(1:1:40), respectively. Invention can be used in machine engineering for making tribotechnical coatings in friction units exploited both with lubricant and without lubricant. Invention provides the enhancement of tribotechnical indices of coatings based on polyamides and providing high level of adhesion indices of coatings on non- -modified metals. EFFECT: improved and valuable properties of composition material. 2 tbl

Description

 The invention relates to polymer materials science and can be used in mechanical engineering for the manufacture of tribotechnical coatings of parts of friction units of machines and mechanisms for various functional purposes.

 In modern designs of machines and mechanisms, composite materials are widely used, from which various coatings are made, including antiwear and anti-friction. Such coatings are based on polymer matrices of various compositions and structures - polymer, polyolefin, polyester, etc. Various modifiers are introduced into the composition of polymer matrices — powders of dry lubricants, oxides, metals, silicates, and other substances that change the strength, adhesion, tribotechnical, and thermophysical characteristics [1]. The content of dispersed fillers in the polymer matrix is from 1 to 40%, which allows a wide control over the performance characteristics of composite materials. However, the introduction of a large amount of filler impedes the ability of the composite coating to form uniform low defect coatings on metals. With a low content of traditional fillers, the required technical effect is not provided.

 Known antifriction coatings based on polymer matrices, mainly polyamide, in the composition of which a powdered polyolefin is introduced as a functional additive [2]. With increasing temperature in the friction zone, a polyolefin having a lower melting point than polyamide forms a melt film on the spots of actual contact with lubricating properties. Such coatings provide high wear resistance of friction units operated both without lubrication and with external lubrication. However, the presence in the composition of the composite material of the polyolefin in the form of an isolated phase sharply reduces the strength of the adhesive bond with metal substrates. Therefore, special methods are required to prepare the surface of metal parts to ensure the required level of adhesive strength of coatings. This significantly complicates the coating process and increases their cost.

The prototype of the invention is a composite material based on polyamide 11, the composition of which introduced anti-friction and anti-wear additives [2]. To ensure the necessary strength of the adhesive bonding of the coating with the metal substrate, the latter is treated with a solution of a special adhesive - a primer based on an epoxy oligomer. After heat treatment of the adhesive in the temperature range of 280-350 ^o C for 5-20 minutes, a sublayer is formed, which provides a chemical interaction of the polyamide macromolecule and the metal substrate. The disadvantage of the prototype is:
- lack of domestic production of polyamide 11, which necessitates the import of this component;
- insufficiently high level of adhesion of the coating to modified surfaces;
- high energy consumption of the coating process and increased environmental hazard due to the solvents and degradation products of the primer used during its heat treatment;
- low tribological characteristics of coatings, especially during friction without external lubrication.

Tasks to which the invention is directed:
- increase the tribological characteristics of coatings based on polyamides;
- ensuring a high level of adhesion characteristics of coatings on unmodified metals.

The tasks are solved in that a modified polyamide is used as a coating matrix, which is a powdery product of cryogenic grinding of a thermomechanically combined mixture of polyamide 6 and polyethylene in a ratio of 10: 1 ÷ 0.1, and as a carbon filler, a mixture of carbon-containing components of various modifications is graphite-like , diamond-like and carbon-graphite fiber in a ratio of 1: 1: 20 ÷ 1: 1: 40 with the following content of components, wt.%:
Carbon filler - 0.11 - 10.5
Modified Polyamide - Else up to 100
The compositions of the composite materials for tribological coatings according to the prototype [1] and the invention are shown in table 1.

 As polyamide 11, a product sold by ELF ATOCHEM, France, under the trademark Rilsan, was used. As a low-pressure polyethylene, the powdered product Kaplen (Russia) was used.

 As high-pressure polyethylene, polyethylene produced by the Novopolotsk Production Association Polymir was used. As an extremely high molecular weight polyethylene, Khostalen GUR (GUR 4120) manufactured by Vauer was used.

The product of cryogenic grinding based on polyamide 6 was obtained as follows. The mechanical mixture of polyamide 6 granules (Grodno PO Khimvolokno) and polyethylene was thermomechanically combined in a screw-type extruder at temperatures of 240-280 ^° C followed by granulation. The granules obtained were subjected to cryogenic grinding in a rotary mill, using liquid nitrogen as a cryogenic agent. The resulting mechanical mixture of fractions was sieved to obtain a product with a particle size of 80-100 microns. As carbon graphite fiber used fiber brand "Viskum" produced by Svetlogorsk PO "Khimvolokno." The fiber was pulverized in a mill of a dismembrator type to obtain a fraction with a size of 50-80 microns. As components of the carbon filler, an industrial product of the UDAG brand manufactured by Cinta CJSC was used. The ratio of diamond-like and graphite-like fraction in the UDAG product is 1: 1. If necessary, the missing amount of graphite-like or diamond-like modification is introduced into the composition of UDAG. The dispersion of the nanoparticles of the UDAG product was 3–10 nm.

To obtain compositions of composite materials used polymer powders with a particle size of not more than 100 microns. The components were mixed in a drum type mixer until a homogeneous composition was obtained. The coatings were applied by the method of a fluidized bed of an air suspension of a composite material. Samples of steel 60 PP preliminarily defatted and heated to a temperature of 250-280 ^° C were used as a substrate ^. The prepared samples were placed in a mechanical suspension, as a result of which the particles of the composite were precipitated and melted to form a coating. The resulting samples were examined after 24 hours by standard methods. Tribotechnical tests were carried out according to the "finger-disk" scheme at a sliding speed of 1 m / s and a load of 5 ÷ 10 MPa. The coating was applied to the end portion of a metal sample of steel 45. The tests were carried out without lubrication and with MC-20 oil, which was fed into the friction zone using a wick. The adhesive strength of the coating was evaluated by peeling at an angle of 180 ^o .

 Tribological and strength characteristics of coatings obtained from composite materials of the prototype and the claimed compositions are shown in table 2. As follows from the data of table 2, the claimed compositions in the claimed ratio of components (compounds II-IV, VIII, IX) surpass the prototype in strength and tribotechnical characteristics. Exceeding the declared content (composition V) does not give an additional effect, and a decrease in the content (composition I) leads to a decrease in the effect. The use of a mechanical mixture of PA11 and HDPE (composition VII) or a mechanical mixture of PA6 and HDPE (composition VI) instead of a cryogenic grinding product of a thermomechanical mixture of HDPE + PA6 leads to a sharp decrease in the strength and adhesive characteristics. The absence of carbon nanoparticles (composition X) in the composition and their replacement with ordinary graphite particles (composition X) reduces the strength and tribotechnical characteristics of coatings on metals.

 Thus, the claimed compositions in the claimed ratio of components surpass the prototype in a complex of physico-mechanical, tribotechnical and adhesive characteristics.

 The invention consists in the following. The thermomechanical combination of polyamide 6 and polyethylene leads to the formation of a copolymer product, which has a higher thermodynamic compatibility compared to a mechanical mixture of components in similar proportions. The introduction of carbon nanoparticles into the polymer matrix provides an additional interaction of PA6 macromolecules and polyethylene due to the orienting action of their own force fields. Orientation leads to the formation of quasicrystalline structures in the amorphous part of the polymer matrix, which increases the strength of the composition and the adhesive interaction of the coating with the metal substrate. The additional introduction of carbon-graphite fiber into the composite strengthens it and improves the tribotechnical characteristics both during friction with lubricant and without lubricant. High adhesion characteristics are inherent in the claimed compositions, not only when applied to a modified metal surface, but also on untreated. This allows you to form a coating in one technological cycle and dramatically reduces the energy intensity of the process.

 Thus, the claimed composition has a feature of the invention according to the criteria of technical and technological effect.

Sources of information
1. Dovgyalo V. A., Yurkevich O.R. Composite materials and coatings based on dispersed polymers. - Minsk: Science and technology, 1992 - 256 p.

 2. Designing for Rilsan coatings. - ELF ATOCHEM, Paris, 1999. -P. 18. - prototype

Claims (1)

Composite material for tribotechnical coatings based on a polyamide matrix and a carbon filler, characterized in that it contains a modified polyamide as a polyamide matrix, which is a powder product of cryogenic grinding of a thermomechanically combined mixture of polyamide 6 and polyethylene in a ratio of 10: 1 ÷ 0.1, and as a carbon filler, a mixture of carbon components of graphite-like and diamond-like modification and carbon-graphite fiber in a ratio of 1: 1: 20 ÷ 1: 1: 40 in the following ratio shenii, wt.%: Carbon filler 0.11-10.5 Modified Polyamide Else up to 100

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