RU1785818C - Method of depositing coatings using metal powders - Google Patents

Abstract

The invention relates to the field of powder metallurgy, in particular to methods for coating surfaces of parts. The purpose of the invention is to reduce energy consumption while maintaining the quality of the coating. A part is placed in the cavity of the matrix and a powder mixture is placed on it. The matrix is rotated with simultaneous application of axial load, while induction heating is carried out. After the low-melting component of the powder mixture is melted, the rotation speed of the matrix is determined from the selected ratio, after which, by applying a braking torque, the part is separated from the matrix and magnetic pulse compression is carried out. The method allows to reduce power consumption and reuse bimetal matrices.

Description

The invention relates to the field of powder metallurgy, in particular to methods for coating surfaces of parts.

The aim of the invention is to reduce energy consumption while maintaining the quality of the coating.

The goal is achieved in that the part with the powder layer formed on it is separated from the dielectric matrix by axial movement relative to the latter. This operation is carried out before the magnetic pulse pressing, and the part with the layer is placed in the inductor, the inner diameter of the working cavity of which corresponds to the outer diameter of the layer. However, the separation of the matrix after crystallization and solidification of the fusible component prevents the connection of the layer

with the matrix as a result of adhesion, which will require significant axial forces to tear the layer apart. The application of great efforts often leads to the destruction of the matrix. With this in mind, the matrix is separated from the layer prior to adhesion. those. before the crystallization of the melt, and establish the necessary speed of rotation about the part.

The expression for determining the velocity ft is obtained from the following condition:

(1)

 00

ate

00

00

where Pp is the capillary pressure on the melt;

The rc pressure of centrifugal forces on the melt of the low-melting component.

The pressure PP is determined from the following expression:

 4 а cos в, „,

PP -HTZ- W.

where (L is the surface tension of the melt with a low-melting component;

c - melt wetting angle by the refractory constituent mixture;

dmax is the maximum diameter of the capillary formed by the pores formed on the part by a powder layer.

The pressure of the centrifugal forces Pc is determined from the following expression:

mu of- RM mu and

RC

 P1Ts

(3)

SK I where GPC is the mass of the powder with a low-melting component;

RM is the inner radius of the matrix;

S is the surface area of the powder layer;

I is the length of the part.

Substituting the values from expressions (2) and (3) in (1) instead of Pc and Pp, we finally obtain the expression for determining the required rotation speed:

a) at 2 UG and cos in G.

 dmax GPZ

Setting the required rotation speed is due to the need to eliminate leakage and spatter under the action of centrifugal forces of the molten metal from the pores of the layer formed on the part after separating it from the matrix. Maintaining the required amount of low-melting component provides a predetermined thickness of the composite electrically conductive layer, the reduction of which reduces the efficiency of magnetic pulse exposure and degrades coating quality.

In order to facilitate overcoming the frictional forces of the rough surface of the sintered powder on the matrix surface during the period of separation of the layer from it, as well as to reduce the applied axial pressure, the high level of which causes destruction of the matrix, it is additionally informed of the braking moment.

The method is carried out as follows. A part is installed in the dielectric die cavity, and a powder mixture consisting of a powder of a coating metal, a powder of non-ferrous metal and a deoxidizing agent such as borax is placed at the ends between the movable punches. The matrix is clamped in the centers and rotate with simultaneous application of axial load to them.

The high-frequency generator is turned on and the charge is induction heated. In the process of heating and compaction of the powder

centrifugal forces simultaneously carry out its continuous axial replenishment. Additional sealing is made towards each other.

5 to each other with punches under the action of a force load applied to the centers. The rotation speed of the matrix with the powder part is set based on the condition that the heating of the powder charge is ensured by high-frequency currents.

After the non-ferrous metal powder is melted, the rotation speed of city is set from relation (4). Upon reaching the required speed of rotation to the part

15, with a layer of sintered powder and a melt of the low-melting component in the pores, an axial force is applied, which allows separating the layer formed on the part from the matrix and moving the part from the molded

coating layer on it into the inductor for

45

fifty

magnetic pulse pressing, In the inductor, the diameter of the working cavity of which corresponds to the outer diameter of the coating layer, 25 is formed compaction of the formed layer by a pulsed magnetic field.

An example implementation of the method. The iron-graphite-copper system is coated on the outer surface 30 of the steel blank of the worm wheel hub.

Parameters of the worm wheel: hub material - steel 45; outer radius. 28 mm; inner radius YaVn.st.19 35 mm, hub width mm; coating material (crown) - iron-graphite powder of ZhGrZ brand (80-82%) and PM1 copper (18-20%), outer radius ННар.вен. 35 mm. Transmission parameters: axial module 3 40 mm; the number of teeth of the wheel 21; ring gear width 54 mm; the number of calls of the worm is 4; profile angle 20; worm material - steel 20X (GOST 4543-61).

Worm wheel hub blank

fixed on a mandrel and installed in the cavity of the matrix with a radius of mm and a width of 90 mm. From the ends of the matrix have cover-punches. In the gap between the hub and the matrix, a powder mixture of these metal powders and a small amount of borax powder, which is finely ground, are placed.

The final porosity after axial compaction is set to 0.4 (, 4). The weight dose of the ZhGrZ iron powder backfill, 816 kg, is required, while the weight dose of PM1 copper powder is 233 kg with the thickness of the composite layer mm. To calculate the value of S (skin layer), 17.1080 m, ml f 20 kHz are received. Based on the calculation data, mm, 8 mm, therefore, the weight dose of RC selected correctly.

The assembly is placed in an inductor connected to the TVCH-LPZ-2-67M generator and rotated at an angular speed of rpm, while an axial pressure of 10 MPa is applied to the powder layer.

In the inductor of the HDTV generator, the powder mixture is heated to a temperature of 1200 ° C, and after spraying the copper powder, the rotational speed of the part is set based on the ratio (4V For calculation, we take Sp.nat 2.3 J / m; cos obtained experimentally dmax 10 3 m; gpc Rts 0.233kg; 8 2lNm1 14.5., Then

SOU at 4 Tspov.nat. COS in 5G - dmax GP Rw

 116.8 rad / s 1115.5 rpm.

According to the proposed inequality, th 1000 rpm is chosen.

As soon as the rotation speed of the part with the layer formed on it reaches 1000 rpm, the latter is moved along the axis of rotation from the matrix and the inductor of the HDTV generator to the MIU inductor, the cavity diameter of which was 85 mm. By pressing the button, the button MIU Impulse-A produces a magnetic pulse treatment with an energy of 4 kJ, after which the rotation is stopped.

As in the known method, a two-layer coating was obtained on the hub of the worm wheel, consisting of composite compact and porous (porosity 16-20%) parts. The adhesion strength of the coating to the steel hub, as well as in the known method, was 140-160 MPa.

Thus, as can be seen from the example, for magnetic pulse processing of a powder layer formed on a part according to the proposed method, ceteris paribus

Under the conditions, an energy of 4 kJ was required, which is substantially less than the energy of 9 kJ used in the known method to obtain a similar coating. Thus, the invention has the following technical and economic advantages:

- the process of producing metal powder coatings is carried out at the maximum efficiency of magnetic pulse pressing;

Claims (1)

- significantly increases the durability of tooling (matrix). The claims A method of producing coatings of metal powders, comprising placing the part in the cavity of the matrix and placing the powder mixture of the coating on it, heating the powder until it melts low-melting component of the mixture, compaction and cooling to crystallization of the melt with simultaneous rotation of the matrix and magnetic pulse pressing of the molded powder layer on the part, characterized in that, in order to reduce energy consumption while maintaining the quality of the coating, before cooling, the rotation speed of the matrix is set from the following ratio Wy 2 iron COS0 i.  dmax T1ts where coy is the matrix rotation speed: a - surface tension of the melt with a low melting component mixture; $ angle of melt wetting of the material by the refractory constituent mixture; I is the length of the part; ymax is the maximum diameter of the capillary formed by the pores in the powder layer formed on the part; ggs - the mass of the powder of the low-melting component mixture, and before magnetic-pulse pressing, the part with the layer formed on it is separated from the matrix by applying a braking torque to the matrix.