RU2604086C1 - Method of multifunctional coatings plasma sputtering - Google Patents

Abstract

FIELD: instrument making.

SUBSTANCE: invention can be used for multifunctional coatings plasma sputtering in instrument making and machine building, as well as in making of intraosseous implants with metal and composite coatings. Working gas is supplied into arc, burning between cathode and copper anode, with plasma jet formation. Sprayed material is supplied into plasma jet by carrier gas on preprocessed surface. Plasma spraying is carried out in vacuum at swinging motion of plasmatron perpendicular to its motion direction and coated surface is additionally exposed to pulsed gas discharges with current of 90±2 A with current pulses duration of 0.2±0.02 s and with pulses repetition frequency of 50±2 Hz. Plasmatron swinging is performed with rolling angle of 15-25° with frequency of 20-40 motions per minute and translation length of 10-15 mm at movement speed of 20-30 motions per minute.

EFFECT: method ensures production of coating formed from particles with optimum adhesion properties and uniformity of coating.

1 cl, 1 dwg, 4 tbl

Description

The invention relates to metallurgy, in particular to a method for plasma spraying of coatings, and can find application in instrument and mechanical engineering, as well as in the manufacture of intraosseous implants with metal and composite coatings.

A known method of plasma spraying coatings (RF patent No. 2283364, IPC: C23C 4/12, publ. 09/10/2006), in which the coating is formed by a stream of particles formed by spraying part of the rod material that is molten in a plasma jet. Spraying part of the rod material is carried out by informing him of ultrasonic vibrations. The arc current of the plasma torch and the distance from the cut of its nozzle to the axis of the bar material are set equal to (120-150) A and (10-15) mm, respectively. The feed rate of the rod material into the plasma jet is determined from the conditions of inverse proportionality of the propagation velocity of the front of the molten material and the preservation of the melt layer at the butt end of the rod material of not more than half the length of the standing wave of ultrasonic vibrations.

This method of plasma spraying coatings is laborious to use and requires additional equipment for its implementation.

A known method of plasma spraying wear-resistant coatings (RF patent No. 2462533, IPC: C23C 4/10, publ. 09/27/2012), which consists in introducing dispersed ceramic powder through an annular gap into an air-plasma jet and then spraying it onto a pre-treated surface of the product. In this case, dispersed particles of aluminum oxide Al2O3 are used with the following ratio of the fractional composition: 20–40 μm in the amount of 75-85% and less than 20 μm - the rest. Spraying is carried out at a plasma torch power in the range of 44-54 kW and an air flow rate of 1-2 g / s.

However, this method is time-consuming and does not allow to obtain uniform coatings with developed surface morphology.

Closest to the proposed solution is a method of plasma spraying of coatings (patent No. 2203977, IPC: C23C 4/02, publ. 05/10/2003), in which a working gas is formed into the arc burning between the cathode and the copper water-cooled nozzle, forming a plasma jet, and the sprayed powder is fed into the nozzle by a stream of conveying gas onto a pre-treated surface. In this case, the sprayed powder is fed into the plasma jet by pulses on the untreated surface, while the ratio of the pause to the powder feed pulse is 4: 1.

However, in the considered method of plasma spraying, the problem of coating formation with high adhesion and uniformity has not been solved.

The objective of the invention is to improve the technology of plasma spraying, which should provide a plasma spray coating formed from particles with optimal characteristics, such as adhesion and uniformity of the coating.

The technical result is to increase the adhesion and uniformity of coatings.

The problem is solved in that when implementing the method of plasma spraying multifunctional coatings, which consists in supplying a working gas to an arc burning between the cathode and a copper anode, and thereby forming a plasma jet, feeding the sprayed material into a plasma jet with a jet of transporting gas to a pre-processed surface, according to the claimed technical solution, the plasma spraying process is carried out in a vacuum environment with a rocking motion of the plasma torch perpendicular to its direction the movements and additionally act on the sprayed surface by pulsed gas discharges with a current of 90 ± 2 A, a current pulse duration of 0.2 ± 0.02 s, and a pulse repetition rate of 50 ± 2 Hz. Also, the oscillating movement of the plasma torch is carried out with a rolling angle of 15-25 ° with a frequency of 20-40 swinging movements per minute and a length of translational movement of 10-15 mm with a speed of 20-30 translational movements per minute.

The invention is illustrated in the drawing: FIG. 1 - Scheme of plasma spraying technology for multifunctional coatings.

The positions in the drawing indicate: 1 - the kinematic link of the translational movement of the plasma torch; 2 - kinematic link of the oscillating motion of the plasma torch; 3 - plasmatron; 4 - plasma jet; 5 - spraying spot; 6 - spraying surface.

The method of plasma spraying multifunctional coatings is as follows.

The spraying surface 6 is preliminarily subjected to mechanical treatment, for example, by jet using an electrocorundum powder with a particle size of 200-250 μm under a pressure of 6.5 atm (Lyasnikova A.V. Dental implants. Research, development, production, clinical application / A.V. Lyasnikova et al. - Saratov: Sarat. State Technical University, 2006. - 254 p .; Lyasnikova A.V. Biocompatible materials and coatings of a new generation: production features, nanostructuring, study of properties, prospects for clinical use / A.V. Lyasnikova etc. - Saratov. Science Book, 2011. - 220)..

Next, the volume of the working chamber of the plasma spraying unit is pumped out with a vacuum system to the required pressure, for example 1 Pa, and filled with a working gas, for example argon. When voltage is applied between the anode and cathode in the plasma torch 3, the plasma arc ignites, into which the working gas is supplied, for example, argon forming a plasma jet 4. The sprayed powder is fed into the nozzle of the plasma torch 3 using a conveying gas jet. Simultaneously with the powder supply, the voltage of the power source is applied between the workpiece and the plasma torch nozzle 3, as a result of which the surface 6 is activated by a pulsed arc discharge with a current strength of 90 ± 2 A, a current pulse duration of 0.2 ± 0.02 s, and a pulse repetition rate of 50 ± 2 Hz during plasma spraying. When spraying the coating on the surface 6 in the spraying spot 5, the plasmatron performs translational (up / down) movements of a length of 10-15 mm with a movement speed of 20-30 translational movements per minute using the kinematic link of the translational movement of the plasmatron 1 and the oscillating movement with a rolling angle of 15 -25 ° and a frequency of 20-40 rocking movements per minute using the kinematic link of the oscillating motion of the plasma torch 2.

The oscillating motion of the plasma torch, perpendicular to the direction of its movement, will allow us to average the characteristics of the sprayed particles and to exclude the influence of the position of the particles in the plasma jet on the quality parameters of the coating. In this case, the most optimal from the point of view of uniformity of coverage of the rolling angles of the plasma torch are 15-25 ° with a frequency of 20-40 swinging movements per minute, and the lengths of the translational movement of 10-15 mm with a speed of 20-30 translational movements per minute. The indicated modes of rolling and translational motion of the plasma torch were selected experimentally and are summarized in tables 1, 2.

When the axis of the plasma jet is perpendicular to the sprayed surface (base), the particle flow is distributed symmetrically with respect to the axis of the jet. Thus, the method of plasma spraying of coatings with the swing of the plasma torch significantly expands the regulation of uniformity of coatings, which in turn will affect the adhesion of the coating to the substrate (adhesion).

The introduction into the plasma process of additional exposure to the sprayed surface of pulsed gas discharges to activate contacting surfaces will contribute to increased adhesion. This is due to many phenomena that occur during the period when the deposited particles are in the plasma jet and in the phase of formation of coating particles (Antsiferov V.N. Powder metallurgy and sprayed coatings / V.N. Antsiferov, G.V. Bobrov, L.K. Druzhinin , S.S. Kiparisov et al. - Moscow: Metallurgy, 1987.- 502-504 p.).

The process of additional exposure to the sprayed surface of pulsed gas discharges can be performed using a wide range of current control. However, the use of small amounts of current leads to a decrease in the productivity of the process, and when using large values of current increases the average temperature of the workpiece, which is unacceptable for some groups of products. Therefore, it is advisable to activate the sprayed surface using a current strength of 90 ± 2 A (table 3).

Also, the duration of the current pulses and the pulse repetition rate have an additional effect on the sprayed surface of pulsed gas discharges. During the experiment it was found that an increase in the pulse repetition rate to a certain limit contributes to an increase in the adhesion strength of the coating. However, when treating a sprayed surface at large values of the duration of current pulses (more than 0.25 s) and pulse repetition frequency (more than 50 Hz), a polymerization process may occur on the surface of the part, which is unacceptable for mechanical engineering products, electric vacuum and medical devices and products. When using small durations of current pulses (less than 0.05 s) and pulse repetition frequency (less than 10 Hz), the activation process will not fully occur.

According to experimental data, it is advisable to use the current pulse duration equal to 0.2 ± 0.02 s and the pulse repetition rate equal to 50 ± 2 Hz (table 4).

Thus, a plasma spraying method has been developed for multifunctional coatings, which as a result allows to obtain a coating with a uniform structure and increased adhesion, which will contribute to the long and reliable operation of products for various purposes.

Claims (2)

1. A method of plasma spraying multifunctional coatings, comprising supplying a working gas to an arc burning between a cathode and a copper anode, with the formation of a plasma jet, supplying a pre-treated surface to a plasma jet of a sprayed material with a conveying gas jet, characterized in that the plasma spraying process is carried out in the vacuum medium during the oscillating motion of the plasma torch is perpendicular to the direction of its movement and additionally act on the sprayed surface by pulsed gas discharge s with a current of 90 ± 2 A current pulse duration 0.2 ± 0.02 sec and a pulse repetition rate of 50 ± 2 Hz. 2. The method according to p. 1, characterized in that the oscillating motion of the plasma torch is carried out with a rolling angle of 15-25 ° with a frequency of 20-40 swinging movements per minute and a length of translational movement of 10-15 mm with a speed of 20-30 translational movements per minute .

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