JPH08302458A - Formation of coating having gradient composition by thermal spraying - Google Patents

Abstract

PURPOSE: To produce a stock having various excellent functions at a lower cost by realizing the formation of a material having a gradient compsn. by a simpler thermal spraying method and forming coating having a gradient compsn. thereon. CONSTITUTION: For forming coating having a gradient compsn., plural powders are individually or mixedly fed to thermal spraying flame and are collided with the material to be thermal sprayed rotating at a high speed, and by the difference in the density in the fused soln. or by the difference in the density of the solidifying temps., the difference in the operation of centrifugal force is utilized, and the coating having a gradient compsn. is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a film by thermal spraying, and more particularly to a method for forming a gradient composition film.

[0002]

2. Description of the Related Art Conventionally, as a method for forming a gradient composition film,
There are a sintering method, a dry process method, a thermal spraying method, and the like.

In the sintering method, materials having a gradient composition in several layers are integrated by pressure sintering or diffusion bonding to form a gradient composition material.

The dry process method includes a method of forming a graded coating by the CVD or PVD method. For example, a cemented carbide substrate on which a composite laminated coating of Ti and Al is formed is put to practical use as a coating tool. There is.

As a thermal spraying method, a ceramic is thermally sprayed on a bond coat layer for stress relaxation formed on a base material as seen in a thermal barrier coating of a combustor liner of a gas turbine to form a composite film. And a graded film forming method in which the intermediate layer is continuously changed from 100% metal to 100% ceramic. Further, in Japanese Patent Application Laid-Open No. 4-268061, a single plasma gun is used, and the average particle size of the starting powder is changed for each component to adjust the molten state, whereby a mixed composition in which all components are dense. A method of forming a film is disclosed.

[0006]

Among the above-mentioned conventional methods, the sintering method is disadvantageous in that the thickness thereof is too large, it is not suitable for forming a film, the apparatus is large, and the processing cost is high. There is.

In the dry process method, the thickness of the film formed is usually as thin as 10 microns or less,
There is a problem that the film cannot be formed to a desired thickness.

Further, the thermal spraying method requires a large amount of equipment cost as an initial investment, a high processing cost, and when a graded composition is to be formed, there is a problem that a higher degree and strict control are required. is there.

Therefore, according to the present invention, a material having a variety of excellent functions can be realized by forming a gradient composition material which has conventionally required a high technology by a simpler thermal spraying method and by forming a gradient composition film. The present invention provides a method for forming a graded composition film, which can be provided at a lower cost and is expected to be widely used from general industrial members to advanced industrial fields.

[0010]

According to the present invention, in order to form a gradient composition coating, a plurality of powders are individually or mixed and charged into a flame spraying frame, and the powders are collided with a sprayed material rotating at a high speed. The gradient composition film is formed by utilizing the difference in the action of centrifugal force due to the difference in the density of the melt or the difference in the solidification temperature. Further, the same effect can be obtained by rotating the material to be sprayed at a high speed during the fusing treatment after the film formation by thermal spraying.

In the present invention, the rotational speed of the material to be sprayed is
The peripheral speed of the rotary spraying surface is required to be 50 cm / sec or more and approximately 300 cm in order that the powder particles melted by the action of the centrifugal force quickly blend into the surrounding spraying surface to form a film having a uniform composition. / Sec or less is preferable.

The present invention can be applied to various materials, but an example of its application will be described.

(1) Bearing By spraying a mixture of Cu, Ni and Babbitt metal on steel, the Cu and Ni components with high bonding strength are increased on the steel side, and the surface layer has a low melting point with good lubricity. A graded composition film containing a large amount of Babbitt metal is formed. In another embodiment, a Cu-Pb alloy sprayed material is sprayed on the steel shaft to form a Cu-rich layer having high strength on the steel side and a Pb-rich layer with low melting point and good lubricity on the surface side. A bearing made of a film having a gradient composition in which is formed is obtained.

(2) Friction material coating Fe, Sn, Pb, etc. having strong strength and bonding force are formed on the inner peripheral surface of steel, and a layer rich in ceramics such as SiO ₂ having a smaller specific gravity is formed on the inner surface layer. Used as a friction material.

(3) Cermet coating A WC-rich layer having a high melting point and wear resistance, and a Co rich layer having a low melting point and a large bonding force with steel, are formed in a graded composition from the surface side to the inner peripheral surface side of steel to obtain wear resistance. Form a cermet film.
Further, as another example, from the surface of the inner peripheral surface of the steel, a TiC rich layer having high wear resistance, a high melting point and a small specific gravity, and a Ni-Mo rich layer having a large bonding force with the steel and a low melting point and a large specific gravity are formed. Gradient composition A heat-resistant composition that forms a wear-resistant film, or has a gradient composition of a ceramic-rich layer with a smaller specific gravity and heat resistance, such as alumina, or a metal-rich layer with a larger specific gravity such as Ni, from the surface of the steel inner peripheral surface. A protective film is formed.

[0016]

According to the present invention, the material to be sprayed is rotated at a high speed to spray a plurality of powders individually or mixed, and the composition of the gradient composition is caused by the difference in the action of the centrifugal force due to the difference in the density of the melt or the difference in the solidification temperature. A film is formed.

[0017]

EXAMPLE A forming method of the present invention will be described with reference to FIG.

FIG. 1 is an explanatory view for carrying out a method for forming a gradient composition sprayed coating.

Material to be sprayed 1 from sprayed powders having different solidification temperatures
When the gradient composition thermal spray coating 2 is formed on the surface of the thermal spray powder a and the thermal spray powder b having a solidification temperature lower than a, the thermal spray frame 5 of the thermal spray gun 4 from the powder supply devices 3a and 3b, respectively.
Then, the mixture of the molten powders 6 is placed in a high-speed, high-temperature gas stream and collided with the surface of the material 1 to be sprayed which rotates at high speed. The molten powder 6 is immediately cooled and solidified on the surface of the material.
At this time, due to segregation due to the difference in solidification temperature, a layer containing the largest amount of powder a having a higher solidification temperature is first formed. Therefore, the remaining portion is a mixture of two molten powder components having a relatively large amount of component b, and the remaining portion that is still in the melt state remains fluid. Therefore, they are collected in the outermost layer of the film by the centrifugal force generated by the high speed rotation. Since the cooling and solidification process is also proceeding in parallel, the next layer based on this remaining melt containing a little more component b than the initial layer is solidified and laminated on the previous layer. In parallel with this, the next mixture of the melted thermal spray powders is newly supplied to the remaining melt, and the next layer based on the melt in which the concentration of the component b is further increased is laminated.
The above process is accelerated with the progress of thermal spraying, and the ratio of this composite progresses to the solid solution limit of the component a and the component b, and thereafter, the composite coating of the upper limit composition of the solid solution limit and the component b is formed. It is sequentially stacked. These processes proceed in parallel at the same time, and thus, the gradient composition coating by thermal spraying can be more easily realized.

Next, in the case of metal-based powders having different densities, as in the above-mentioned embodiment, the mixture in the molten state is placed on a high-temperature and high-speed gas stream to collide with the surface of the sprayed material rotating at high speed, When the material to be sprayed is rapidly cooled, the alloy component coating having a low density, in which the action of centrifugal force is smaller, is solidified and fixed on the surface of the material to be sprayed. In parallel with this, when a mixture of molten powder is newly supplied and integrated with the previous residual liquid, a melt having a slightly higher density than before is obtained. This is cooled and solidified and laminated and fixed as the next layer. These series of processes are continuously performed one after another during the thermal spraying, and as a result, a graded composition film having a density gradient is formed in the direction in which the centrifugal force acts.

At this time, by mounting the thermal spraying material on the outer peripheral surface of the rotating circumference, a coating whose density increases toward the coating surface is formed. However, the thermal spraying material is mounted on the inner rotating surface of the rotating circumference. For example, it is possible to form a graded composition film whose density increases toward the inside of the film. Further, when using a powder having a high melting point such as ceramics and a metal powder having a low melting point as the powder for thermal spraying, if the spraying condition is set to the low melting point powder side,
The thermal spray coating has a form in which the low melting point metal fills the space between the semi-molten powders, but since the material to be sprayed rotates at high speed, the low melting point metal in the molten state flows between the solidified and fixed particles, It is possible to form a particle-dispersed sprayed coating in which the content ratio of the low melting point metal increases in the direction of action of centrifugal force.

Further, in the self-fluxing sprayed coating, the same effect can be obtained by rotating the sprayed material at a high speed during the fusing treatment after the coating is formed.

In the above method, the thermal spray powder is fed by
They may be used individually or as a mixture, and in order to improve the effect, the powder supply amount may be time-staggered so that a roughly gradient composition is obtained.

Next, specific examples will be described.

(Embodiment 1) 300 torr argon atmosphere, plasma output 35 kw, spraying distance 110 mm, spraying material rotating radius 75 mm, peripheral speed 250 cm / sec.
n, copper powder was fed at about 15 g / min to perform plasma spraying, and a copper-rich, copper-aluminum, and aluminum-rich gradient composition sprayed coating was obtained toward the coating surface layer portion having a film thickness of 100 microns. .

(Embodiment 2) 300 torr argon atmosphere, plasma output 35 kw, thermal spraying distance 110 mm, thermal spraying material turning radius 80 mm, peripheral speed 150 cm / sec.
When about 20 g / min of copper powder was fed and plasma spraying was performed, a lead-rich, lead-copper, and copper-rich graded composition spray coating was obtained toward the surface layer of the coating having a film thickness of 90 microns. The surface layer was a copper-lead alloy containing 50% of lead, and a bearing material having an appropriate composition was obtained.

(Embodiment 3) About 20 g / min of tungsten carbide powder and about 10 g / min of cobalt powder on the inner peripheral surface side of steel at 300 torr argon atmosphere, plasma output of 40 kw, spraying distance of 100 mm and peripheral speed of 300 cm / sec.
Was supplied and plasma sprayed to form a WC-Co film having a film thickness of 100 μm. The surface layer portion of this coating was a tungsten carbide rich layer having excellent wear resistance, and the inner surface side of the steel was a cobalt rich layer having good sinterability with steel.

(Embodiment 4) 300 torr argon atmosphere, plasma output 35 kw, thermal spraying distance 110 mm, thermal spraying material rotating radius 75 mm, peripheral speed 250 cm / sec.
When plasma spraying was carried out by feeding about 5 g / min of SiO ₂ powder, a film having a film thickness of 100 μm was obtained.
The surface layer portion of this coating was a particle dispersion type in which SiO ₂ was dispersed in aluminum, the contact surface with the material to be sprayed was aluminum, and the intermediate layer was a molten composite phase of SiO ₂ and aluminum.

[0029]

The effects of the present invention are as follows.

(1) According to the present invention, a low-cost gradient composition material can be easily formed, and the composition change can be changed more linearly.

(2) The gradient composition material according to the present invention can be used in a wide variety of fields such as bearings, cermet heat resistant coatings and friction material coatings.

(3) The direction of the gradient composition can be selected by making the sprayed surface of the material to be sprayed the inner peripheral surface or the outer peripheral surface.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a method for forming a gradient composition sprayed coating.

[Explanation of symbols]

1 sprayed material, 2 gradient composition sprayed coating, 3a, 3b
Powder feeder, 4 spray gun, 5 spray frame,
6 molten powder

Claims (4)

[Claims] 1. A method for forming a gradient composition coating, comprising spraying a plurality of powders individually or mixed on the surface of a material to be sprayed which rotates at a high speed. 2. The method for forming a gradient composition coating according to claim 1, wherein powders having different solidification temperatures are individually or mixed and sprayed onto the surface of the material to be sprayed that rotates at a high speed. 3. The method for forming a gradient composition coating according to claim 1, wherein powders having different specific gravities are individually or mixed and sprayed onto the surface of the material to be sprayed which rotates at a high speed. 4. The method for forming a gradient composition coating according to claim 1, wherein the thermal spray coating rotating at a high speed is subjected to a fusing treatment.