The surface preparation method for plasma coating

 

(57) Abstract:

The surface preparation method for plasma coating includes machining with the simultaneous influence of ultrasonic vibrations and static pressure, the maximum value of the amplitude of ultrasonic vibrations set at 18-20% more than the radius of the minimum particle size of the sprayed material. The invention improves the quality of the coating by increasing the strength of its adhesion to the basis and ensure homogeneity of the coating properties under specified conditions. 1 Il., table 1.

The invention relates to mechanical engineering and can be used for preliminary preparation of surface for coatings.

The known method of plasma spraying [1], which consists in the introduction into the plasma jet generated in the arc plasmatron, particles of coating material with the subsequent direction of flow on the surface. Due to the fact that the particles of coating material to a certain extent, melt, are accelerated and collide with the surface, which results in the formation of the coating.

The main disadvantage of this method of plasmin MPa. To improve the adhesion of coating to the substrate is applied prior methods of processing the substrate surface.

There are also known methods of preparing surfaces [2], including surface preparation blasting the oxide and the application of thermal spray coatings, which before the flapper oxide conducting surface plastic deformation blasting method balls made of high-strength steel, and the diameter of the balls is 2 - 3 mm, and the specific energy impacts on the surface during blasting treatment is 105- 106J/m2at specific time effects on the surface of 0.1 - 0.3 min/cm2.

The disadvantage of analog is low adhesive properties of the coating, due to the lack of a transition zone between the base and the floor.

In addition, the known method of surface preparation details [3] before coating thermal spraying, including Electromechanical processing surface of the workpiece by the tool at a pressure of 50 to 80 kgf/cm by passing electric current at the site of contact to melting and movement of the tool, and the processing performed by the tool with a profile about the but in the plane perpendicular to the processed surface with periodic off the electric current. The electric current is disconnected before moving the instrument up. Electric current is also cut off after contact of the tool with the surface.

However, local melting leads to structural transformation, which in turn leads to a weakening of the strength properties of the material. The reciprocating movement of the tool and the melting of the metal causes a change in the metal structure, since sharp edges are stress concentrators, which reduces the fatigue strength of the metal.

The closest in technical essence and the achieved result claimed is a method of coating [4], including preliminary machining of the surface of the product within 1 to 2 seconds and the application of the powder material with simultaneous machining the deposited layers, wherein the mechanical treatment is carried out at a pressure of 50 to 300 N with simultaneous influence of ultrasonic vibrations of a frequency of 16 to 20 kHz and an amplitude of 10 to 80 μm.

The disadvantage of the prototype is a small amount of adhesion and essential to what toroi aim of the claimed invention, is to improve the quality of the coating by increasing the strength of its adhesion to the core and ensure homogeneity of the coating properties under specified conditions.

This object is achieved in that in the method of surface preparation for coatings, including machining and simultaneous influence of ultrasonic vibrations and static pressure, in contrast to prototype create guaranteed the transition zone at the surface by introducing particles of coating material in the base.

Maximum amplitude of the ultrasonic vibrations set at 18 - 20% more than the radius of the minimum particle size of the sprayed material.

Surface properties embedded in it by the coating particles closer to the properties of the coating particles than those of the untreated surface. During subsequent plasma processing surface with uniformly embedded in it particles of the coating will provide a more intensive course of physical and chemical processes responsible for the strength of coupling. This is due to the chemical activity of the Foundation, provide a high level of plastic deformation and greater surface continetti, inherent in this method. Set ratio of amplitude of ultrasonic oscillations and particle size of the sprayed material minimize the number of idle strokes of the tool on the surface and ensures the formation of the transition zone. Mechanical action of the tool directly on the surface and not to the particles, it is undesirable. This does not lead to the formation of the transition zone, and it gets smaller.

The main purpose ultrasonic waterjet processing - cleaning, strengthening and remove burrs and other surface defects. During the indicated operation, the workpiece is placed in a chamber with a water jet, and ultrasonic waves are radiated into the solution. The purpose of the radiation in the solution - cavitation destruction of burrs and additional processing abrasive grains. Upon the occurrence of acoustic streaming abrasive grains and the workpiece due to the different densities and sizes receive different speed. When mutual slippage of the abrasive grains and components deburring.

Unlike waterjet processing, where ultrasonic vibrations are transmitted to the liquid, which contains abrasive particles in the claimed method of ultrasounds is UNT plays the role of the hammer, statically acting on the particles of the powder coating and periodically hitting them, introducing the particles into the surface. The organization of such a process allows to obtain a homogeneous and uniform transition zone containing particles of powder coatings, high surface roughness and the degree of plastic deformation, and as a result increases the adhesion strength and align its quantitative characteristics at different points on the surface.

At the same time, the proposed solution differs from the known method of ultrasonic machining brittle materials, which is described in the works of Professor Markov, A. I. [5]. These two compared methods have different goals. The first is the increase of adhesion of coatings by creating a transition zone containing particles of the coating and having a surface layer of high roughness and the degree of strain hardening, the second one - dimensional forming of brittle materials by chipping microscopic volumes. Ultrasonic dimensional processing is not used when forming materials having the criterion fragility 1<tx<2, because the effect of the introduction of grains in the surface is I positive because it allows you to form a transition zone containing particles of the coating and a rough surface with a high degree of plastic deformation. When processing the surfaces of solid materials introducing abrasive particles into the surface will not occur. However, micromicrocuries surface will allow you to create a measure of roughness, which is other ways to get difficult.

Operation of the proposed method implemented by the device (Fig. 1) containing the processed base 1, through which particles of the coating material 2 in the treatment area, at the same time are affected by the tool 3 static pressure and ultrasonic vibrations.

The essence of the method consists in the following. On the table ultrasonic installation fix the processed base 1. The powder particles of the coating 2 is injected into the treatment area and then simultaneously fail ultrasonic vibrations and static pressure from the tool 3 to the specified particle 2, which, taking root in the basis 1, create a transition zone, while providing a high surface roughness and the degree of plastic deformation of the substrate surface.

An example of a specific implementation of the inventive method.

The diameter of the ultrasonic vibrator tool 30 mm vibration Frequency of the ultrasonic vibrator 22 kHz, the oscillation amplitude of 20 to 25 μm. Pressing force of the tool to the workpiece surface (static load) - 50 N. Processing time 1 - 2 C. Preliminary surface treatment is carried out in a liquid medium. As abrasive particles were used camofluage powder PG-SR GOST 21448-75, the hardness greater than Hrc 45, a particle diameter of 40 to 160 μm. The weight ratio of abrasive particles and fluids 1: 2. After the surface preparation was carried out spraying of the same powder on the installation of the UPA-3M.

The mode of deposition.

Current, A - 350 10

Voltage - 55 2

The spraying distance, mm - 120

The plasma gas flow:

argon, m3/h 0,6

nitrogen, m3/h 0,03

The flow rate of the powder material, kg/h 0,6 - 0,7

The coating thickness, mm - 0,4

Comparative results of the proposed method and the prototype are presented in the table (see the end of the description).

Thus, the claimed solution has a new feature - the ability to create guaranteed transitional PI surface, with the transition zone, characterized by high roughness and the degree of plastic deformation. These factors also contribute to improving the quality of the coating during subsequent plasma processing.

Sources of information:

1. Hasui A. spraying Technique. M. "Engineering". 1975. 232 S.

2. RF patent N 1804148, IPC6C 23 C 4/02, publ. 20.11.96.

3. RF patent N 2068025, IPC6C 23 C 4/02, publ. 20.11.96.

4. A. S. USSR N 1274328, MKI4C 23 C 4/02, publ. 15.03.93 prototype.

5. Markov, A. I. Ultrasonic processing of materials. M Engineering. 1980. 237 C.

The method of surface preparation for coatings, including machining and simultaneous influence of ultrasonic vibrations and static pressure, characterized in that the maximum amplitude of the ultrasonic vibrations set at 18-20% more than the radius of the minimum particle size of the sprayed material.

 

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