JPH06293952A - Thermal spraying method for improving film property - Google Patents

Abstract

PURPOSE:To improve the wear resistance and adhesion of a film at the time of applying thermal spraying on the curcumferential surface of a rotating cylindrical material by pressing a press roller on the material surface immediately after thermal spraying at a specified contact pressure. CONSTITUTION:A cylindrical material 1 to be sprayed is rotated, and thermal spraying is applied from a thermal spraying gun 3 to form a film. At this time, a press roller 2 having a rotating shaft parallel to the rotation axis of the material 1 is arranged directly behind the gun 3 with a partition plate 4 in-between, and a contact pressure at >=10MPa is applied on the material surface. Consequently, the pore is pressed at a high temp. immediately after spraying, the diffusion between a film and the substrate is promoted, and the wear resistance and adhesion of the film are improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal spraying method for further improving the abrasion resistance of a coating as well as properties such as adhesion when performing thermal spraying to improve the abrasion resistance of the surface of a cylindrical material. .

[0002]

2. Description of the Related Art There are various thermal spraying methods such as plasma spraying, gas flame spraying, and explosive spraying, all of which contain several percent or more of the total volume of pores, and most of the coating and substrate are mechanical. Since it is only bonded to the film, peeling of the film frequently occurs during use, and its adhesion is always a problem.
Further, since the coating has pores and microcracks, it has lower hardness, toughness, etc., and inferior wear resistance as compared with a bulk material of the same composition.

Conventionally, there is no method of pressing the pores by using a pressing roller in order to improve the properties of the thermal spray coating, but a method of providing an intermediate layer between the base material and the outermost surface layer, or by heating after thermal spraying Only the method of melting and reducing the pores is known. These are, for example, "Go Inoue
Others: Materials and Process (CAMP-ISIJ), Vol.4 (1991), 477 /
480 "," Shujiro Ono et al .: Thermal spraying technology, Vol.12 (1992), 4 "
5/54 ”and so on. However, for a processing tool such as a rolling roll used under a higher load, the soundness such as adhesion is insufficient, and it hardly leads to practical use.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermal spraying method which improves the wear resistance of a coating and the adhesion thereof.

[0005]

In order to solve the above problems, the present inventors installed a pressing roller adjacent to the spray gun and sprayed while pressing the material to be sprayed, so that the pores were formed at a high temperature immediately after the spraying. It is characterized by improving wear resistance and adhesiveness by utilizing the effect of promoting the diffusion with the base material at the same time as pressing. That is, the gist of the point is that when a cylindrical material is sprayed on the circumferential surface while rotating, a pressing roller having a rotation axis parallel to the rotation axis of the material is arranged immediately after the spray gun. A thermal spraying method for improving the properties of a coating, characterized in that thermal spraying is performed while pressing the material at a contact surface pressure of 10 MPa or more.

[0006]

The present invention will be described in detail below. When performing thermal spraying on a cylindrical material, it is usual to rotate the material and at the same time move it in parallel in the longitudinal direction, and repeat this to obtain a film of a predetermined thickness. The number of repetitions (number of layers) is several times to several tens of times. Since the conventional method does not perform any treatment during this period, the spray particles are simply laminated. Therefore, voids, pores and the like remain as they are between particles, between layers or at the boundary with the substrate. Therefore, the inventors of the present invention invented a method of mechanically crushing voids and the like layer by layer in a high temperature state immediately after thermal spraying and promoting diffusion of boundaries by heating during the next treatment.

In order for the method to be effective, the pressing force must first be sufficient to crimp the air gap. Although there are many types of materials used for thermal spraying, the deformation resistance is a minimum of 10 MPa or more when the temperature immediately after thermal spraying is several 100 ° C. or more, so the pressing force was set to 10 MPa. In the case of ordinary materials, it is preferably 100 MPa or more. If the pressing force is less than 10 MPa, the film cannot be deformed to press the pores.

Most of the materials to be sprayed are iron and steel, and as the spraying material, a mixture of a metal such as nickel, cobalt and chromium with ceramic powder, or a simple metal such as nickel, stellite, stainless steel and molybdenum is often used. . These thermal spraying methods include a plasma method, a gas flame method and a gas explosion method.

In order to increase the pressing force, it is preferable to reduce the diameter and width of the pressing roller. The width is preferably about the same as the spread width of the thermal spray material ejected from the thermal spray gun. When reducing the diameter, it is possible to install a reinforcing roller. The upper limit of the pressing force is the maximum stress that does not cause plastic deformation of the base material. The material of the pressing roller is not particularly limited, but a material that does not cause transfer of the thermal spray material is preferable.

Next, chemical bonding is performed by diffusion between the interfaces such as voids and the like caused by pressure due to heat from the upper layer pile which is subsequently performed. Although the time of exposure to high temperature is short, it is sufficient if diffusion near the interface takes place. If the time is too long, an intermetallic compound or the like may be produced, which may be undesirable.

In this way, the adhesion strength between the sprayed particles and between the layers is increased. Further, in order to prevent the sprayed material from scattering and adhering to the pressing roller, it is preferable to install a partition plate between the spray gun and the roller.

[0012]

FIG. 1 shows an embodiment according to the present invention. The material to be sprayed 1 is S45C steel with a diameter of 400 mm, its rotation speed is 30 rpm, and the pressing roller 2 has a diameter of 150 mm and a width of 50 mm.
The cast steel, the pressing surface pressure is about 130 MPa. The contact position of the pressing roller is about 10 from the center where the thermal spray material hits.
It is 0 mm. 3 is a thermal spray gun and 4 is a partition plate. The thermal spraying conditions are as shown in Table 1. When cold rolling of a steel sheet was carried out using the rolls manufactured by this method, there was no peeling of the coating and wear resistance, that is, roll life was increased to 2.5 times that of conventional rolls made of forged steel. Table 2 shows comparative data of adhesion strength by a shear test method known as an adhesion evaluation method. The adhesion strength is improved to 1.6 times or more depending on the presence or absence of the pressing roller.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

As described above, when the thermal spraying method with improved coating properties according to the present invention is applied, the adhesion and wear resistance of the coating are improved, and the life of tools such as rolls with severe load is improved. Since it can be improved at low cost, it can contribute to reduction of production cost and improvement of quality and efficiency.

[Brief description of drawings]

1 shows an embodiment according to the method of the invention.

[Explanation of symbols]

 1 Material to be sprayed 2 Pressing roller 3 Spray gun 4 Partition plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Matsuo Ataka 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Corporate Technology Development Division

Claims (1)

[Claims] 1. When a cylindrical material is sprayed on the circumferential surface while rotating, a pressing roller having a rotation axis parallel to the rotation axis of the material is arranged immediately after the spray gun.
A thermal spraying method for improving the properties of a coating, which comprises spraying while pressing the material at a contact surface pressure of MPa or more.