JPH08965B2 - Method of supplying thermal spray material - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an improvement in a method of supplying a thermal spraying material for externally supplying a thermal spraying material powder to a plasma spraying apparatus for coating various materials. The present invention relates to a method for supplying a thermal spray material, which has an improved adhesion rate and improved denseness and adhesion of the thermal spray coating.

Background Art In the early 20th century, thermal spraying originated from the technology of melt-spraying low-melting-point metals, and developed mainly for thermal spraying of metals.
In recent years, a film of a high temperature material has been formed using plasma as a heat source.

 The characteristics of plasma spraying are as follows.

Since a high temperature frame of 10000 ° K to 20000 ° K is used,
High melting point ceramics and metals can be sprayed.

Since we use high speed frames from subsonic to supersonic,
The spray speed of particles of thermal spray material is high and the adhesion strength of coating is high.

 The spray output can be controlled easily and accurately.

Since the atmosphere can be set by selecting the gas type,
A film can be formed in various atmospheres suitable for thermal spraying.

Plasma spraying has been utilized and developed in various fields because it can easily form a coating film that can impart various functions such as corrosion resistance, abrasion resistance, and heat resistance by taking advantage of such characteristics.

The plasma spraying gun of plasma spraying is also characterized in that the efficiency of conversion of heat and momentum that can actually be used for spraying is low due to the effects of maintaining the electrode to be cooled with water and entraining outside air.

Therefore, in plasma spraying, the molten state changes depending on the properties of the powdered spray material to be supplied, and the deposition rate obtained by dividing the weight of the coating after deposition by the weight of the sprayed material supplied or the generation of pores generated in the coating There is a problem that the amount (hereinafter referred to as the amount of pores) is likely to fluctuate, and the adhesion strength of the coating to the substrate is difficult to stabilize.

Therefore, conventionally, various techniques have been developed such as selection of gas type, finer particle size of thermal spraying material powder, reduction of entrainment of outside air, etc. to improve the adhesion rate, the amount of pores and the adhesion strength.

In addition, various methods have been implemented as a method for supplying the thermal spray material powder (hereinafter referred to as powder).

The method of supplying the thermal spray material is roughly classified into an internal supply method and an external supply method depending on the positional relationship between the torch portion of the plasma spray gun and the powder supply pipe.

As shown in FIG. 6, the internal supply system has a powder supply pipe (14) built-in near the nozzle (12) of the torch (11), which can supply the powder to the high temperature region of the plasma flame and melt the material. The adhesion rate and the film adhesion strength are improved because the heat treatment is completed, but there is a problem that the supply amount is limited because the molten particles easily adhere to the inner surface of the nozzle (12). Since the supply pipe is built in, there is also a problem that the nozzle structure becomes complicated.

On the other hand, in the external supply method, as shown in FIG. 5, since the supply pipe (14) is arranged in the vicinity of the injection port (13) of the nozzle (12), the powder supply amount can be easily increased. However, the material powder cannot reach the high temperature region of the plasma flame (8) (see powder locus 10 in Fig. 5), melting tends to be incomplete, and the adhesion rate decreases, so the supply amount There is a problem of constraints.

It is also possible to increase the amount of powder carrier gas, but unlike power adjustment, it is difficult to finely adjust the amount of gas according to the type of powder and spraying conditions, and its responsiveness is lacking. Penetrate through the plasma flame (8).
(See a), there is a problem that fluctuations of the plasma flame (8) occur due to an increase in the inclusion of outside air.

In order to make the powder reach the high temperature region of the plasma flame with this external supply method, there is a method of inclining the powder supply pipe (14) toward the injection port (13) of the nozzle (12) as shown in FIG. However, there was a problem that the mouth of the supply pipe (14) was easily damaged.

SUMMARY OF THE INVENTION In view of the present circumstances, the present invention aims to improve the method of supplying a thermal spray material for externally supplying powder to a plasma spray apparatus for coating various materials, increasing the thermal spray amount, and coating deposition rate. It is an object of the present invention to provide a method for supplying a thermal spraying material, which is intended to improve the thermal conductivity, the denseness of the thermal spray coating, and the adhesion.

Structure and effect of the present invention The present invention has variously studied for the purpose of increasing the amount of thermal spraying, improving the coating deposition rate, and improving the denseness and adhesion of the thermal spray coating. As a result, a plurality of powder supply pipes are orthogonal to the central axis of the nozzle. It was discovered that the initial purpose can be achieved by arranging the same angle on the same plane with respect to the central axis.

That is, according to the present invention, in a method for supplying a thermal spray material to a plasma flame of a plasma thermal spraying apparatus, in which a thermal spray material made of powder is gas-conveyed and supplied by a powder supply pipe disposed outside, one plasma flame of a plasma jet torch. On the other hand, two or more and five or less powder supply pipes are made to intersect each other at one point of the plasma frame center axis on one plane orthogonal to the plasma frame center axis of the torch, and plasma A method for supplying a thermal spraying material, characterized in that the powder is carried from each supply pipe at equal angles around the frame central axis, and the powder is jetted in a direction orthogonal to the central axis of the plasma frame and collides with each other in the plasma frame. Is.

More specifically, the powder supply pipes on one plane orthogonal to the central axis (4) of the plasma flame (8) coming out from the injection port (3) of the torch (1) are arranged, for example, in two pieces. The powder supply pipes (5) and (6) are equiangular around the central axis (4) of the plasma flame (8) as shown in FIGS. 1 and 2.
180 °, that is, the feed tube axis (7) is aligned on one axis orthogonal to the plasma flame center axis (4) of the torch (1) at a point 0, and in the case of three, As shown in FIG. 3, each supply pipe axis (7) intersects at one point (0) of the plasma frame center axis (7) and is arranged at an equal angle of 120 ° around the plasma frame center axis (4). Four, five
In the case of the book, they are similarly arranged around the central axis (4) of the plasma flame at equal angles of 90 ° and 72 °.

Taking the above-mentioned supply pipe arrangement, by injecting the powder carrying the gas from each supply pipe in the direction orthogonal to the central axis of the plasma frame and colliding with the plasma frame, the flight distance of the powder in the plasma frame is long, It sufficiently melts, the coating deposition rate is improved, the amount of thermal spraying can be increased, and the effect of improving the denseness and adhesion of the thermal sprayed coating can be obtained.

In the present invention, the supply pipes are arranged on one plane orthogonal to the plasma flame central axis of the torch, the supply axes intersecting at one point of the plasma frame central axis, and arranged at equal angles around the plasma frame central axis. Is characterized by. Therefore, even if two supply pipes (5) and (6) are used as in the arrangement of supply pipes performed in so-called graded spraying shown in FIG. Unless it is arranged at an unequal angle around the central axis (4), that is, facing each other, the effects of the present invention in thermal spraying of various powders and applications cannot be obtained, as will be apparent from the examples described later. In this case, an angle (less than 180 °) to a certain axis (eg vertical axis)
The present invention is arranged in consideration of the influence of gravity on the powder, which is different from the gist of the present invention.

Further, when the number of powder supply pipes exceeds 5, dimensional restrictions are placed on the arrangement of the supply pipes, and a large pulsation occurs in the discharge amount of powder by the carrier gas, which is not preferable, and the effect of improving the adhesion rate is not achieved. Although it can be obtained, it is not preferable because it causes a decrease in melting such as melting only on the surface of the powder, resulting in a decrease in film density and a decrease in adhesion.

Preferred Embodiments of the Invention Preferred conditions in the powder supply mechanism according to the present invention will be described below.

In the present invention, the plurality of powder supply pipes of 2 to 5 are
Each supply pipe axis is orthogonal to the plasma frame center axis, and 1
It is necessary to cross at points. This is indispensable for efficiently colliding the powder from each supply pipe with the high temperature region of the plasma flame when the same weight of powder is supplied from each supply pipe with the same amount of carrier gas. This is a condition, and the closer the intersection of the supply tube axis and the plasma flame center axis is to the nozzle, the more advantageous it is for thermal spraying of the high melting point material.

Further, the supply pipes arranged on one plane orthogonal to the plasma frame center axis are arranged at equal angles around the plasma frame center axis, so that the powder from each supply pipe can be efficiently used in the high temperature region of the plasma frame. It is well supplied and the powder melts uniformly.

Generally, it is necessary to increase the kinetic energy of the carrier gas in order to surely collide the powder with the high-speed plasma frame, but it also cools the plasma frame, and the amount of carrier gas is well selected. It is indispensable for performing proper thermal spraying.

In the present invention, the amount of carrier gas per supply pipe is preferably 7 to 10 in volume ratio with respect to the working gas.
When the volume ratio is less than 7, the powder transport energy is lowered and it becomes difficult to feed the powder. When the volume ratio is more than 10, the collision of the powder particles proceeds smoothly, but the flame temperature is lowered and the molten state is deteriorated. Not preferable. Also, when spraying a high melting point oxide-based ceramic material, etc., increase the carrier gas amount, and when spraying a metal with a low melting point that is susceptible to chemical changes, reduce the carrier gas amount. Therefore, it is necessary to select it appropriately according to the thermal spraying conditions of the required application.

In the present invention, collision of powder from different supply pipes in the plasma flame (8) (see powder locus 10 in FIG. 1)
In fact, because of the high speed of the plasma, as shown in FIG. 1, the point deviated from the intersection (0) of the central axis (4) and the supply tube axis (7) to the substrate (9) side. It occurs at (0 '), but by maintaining the above-mentioned carrier gas amount, the (0') point can be set within the region of 10,000 ° K or higher of the plasma flame, so that the Can be melted and sprayed well.

Further, in the present invention, in order to cope with the decrease in plasma flame temperature due to the use of a plurality of powder supply pipes,
This can be achieved by appropriately selecting the mixing ratio of the working gas and the spraying distance.

For example, the working gas, with _{Ar-N 2, Ar-H} 2 plasma jet, the mixed gas quantity ratio to operate in the range of 100 / 0-70 / 30. In this way, by adding the secondary gas of N ₂ or H ₂ ,
It is advisable to increase the heat quantity of the plasma flame.

Generally, the thermal spraying distance is set within a range of 50 mm to 200 mm in consideration of thermal influences such as heat distortion or melting of the base material. The spraying distance in the method of the present invention is preferably set to 0.75 l to 0.90 l with respect to the conventional set spraying distance 1 under the same operating conditions and powder. That is, although the mixed gas amount ratio is converted, the amount of powder and the amount of carrier gas increase, so the distance setting becomes short.

As described above, in the present invention, in order to increase the amount of thermal spray, the plasma jet of the heat source is highly heated, and the thermal spray distance is shortened to retain the heat of the molten powder, and the radiant heat of plasma is used. It is advisable to select the operating conditions as appropriate in consideration of the various conditions.

In the method of supplying powder according to the present invention, by appropriately selecting so as to satisfy the above-mentioned various conditions, the defect of increase of powder amount and carrier gas amount, that is, increase of cooling material is compensated. The more evenly and reliably supplied powder collides with the central axis of the plasma flame to receive heat, melt,
While flying, at this time, the powder that tends to radiate radially after the collision is pushed back toward the base material by the plasma flame, which increases the flight distance and heat receiving time, improving the overall melting efficiency. The coating rate is improved. Also,
Since the melting is sufficient and good, the density is further improved and the adhesion to the substrate is also improved. Therefore, while maintaining good film formation, the powder supply amount can be increased and the thermal spray amount can be greatly increased.

Examples Example 1 Chamotte brick (fire resistance; SK-32, apparent porosity 25.0%)
The burning surface of is the sprayed substrate surface, Al ₂ O ₃ 90%, balance TiO ₂ and
Using a powder made of SiO ₂ , Ar-N ₂ plasma jet,
In the powder supply method according to the present invention using the two supply pipes shown in FIG. 1, thermal spraying was performed under the conditions shown in Table 1 to obtain a height of 7.
A beat-shaped sprayed work piece having a length of 5 mm and a length of 100 mm was prepared.

The adhered weight of each obtained construction body was measured, and the porosity of the construction body was measured with a porosimeter. The measurement results are shown in Table 1 together with the implementation conditions.

For comparison, the thermal spraying (conventional example 11) by the conventional supply method using one supply pipe shown in FIG. 5 and the two supply pipes shown in FIG. The same spraying as the set conventional grided spraying (conventional example 12)
It carried out on the operating condition shown in Table 1, the adhesion weight of each obtained construction body was measured, and the porosity of the construction body was measured with the porosimeter. The measurement results are shown in Table 1 together with the implementation conditions. In addition, the adhesion weight and the amount of pores are shown as indices with 100 being the case of the conventional thermal spraying work using one supply pipe. The carrier gas volume (V / line) and operating current were constant.

As is clear from Table 1, when the powder supply method according to the present invention was used for thermal spraying, the adhesion amount was improved by 20% or more as compared with the conventional method, and the porosity was also significantly suppressed. In addition, the conventional 2
In the thermal spraying using the supply pipe of the present invention, although the adhesion rate was slightly improved, the thermal sprayed product was porous and could not be put to practical use.

Example 2 The surface of plain steel (SS-41) blasted with # 60 alumina grit was used as the surface of the sprayed base material, and Ni-9Cr-6Al alloy powder was subjected to Ar-H ₂ plasma treatment in Table 2. Thermal spraying was performed under the conditions shown below to form a 0.5 mm-thick coating on the surface of a 50 mm × 100 mm substrate. Also, the output current was kept constant.

The adhered weight of each obtained construction body was measured, and the adhesion strength was measured, and then the porosity of the construction body was measured with a porosimeter.

The adhesive strength is evaluated by the torque when a bottle (made of SS-41) with a cross section of 2 cm ² is fixed on the film with epoxy resin and the torsional strength is measured with a torque wrench, and the pore volume is measured by the adhesive strength. The subsequent bolt was heat-treated at 300 ° C. to incinerate the resin, and the film recovered was measured.

Further, for comparison, thermal spraying by a powder supply method using six supply pipes (Comparative Example 15) and thermal spraying by a conventional supply method using one supply pipe shown in FIG. 5 (Conventional Examples 13, 14). )
Was carried out under the operating conditions shown in Table 2, and the adhesion weight of each of the obtained constructions was measured, and the adhesion strength and the porosity of the construction were measured. Note that the adhered weight and the amount of pores are expressed as an index with 100 in the case of a conventional sprayed work piece with a single supply pipe, and as a relationship with the powder feed rate (g / min)
Shown in Figures and 9.

As is clear from Table 2 and the results of FIG. 8 and FIG. 9, the thermal spraying of the supply method according to the present invention has a significantly increased amount of adhesion, and even if the powder supply is doubled, The generation of pores can be suppressed to be equal to or less than the pore volume of
It can be seen that the adhesion of the coating is greatly improved and extremely good thermal spraying is possible.

Example 3 Using a silica stone brick preheated in an electric furnace as a base material, SiO ₂ 80 wt%-
Al ₂ O ₃ 15 wt% SiO ₂ -Al ₂ O ₃ series refractory aggregates were heated by a plasma gun sealed in a water-cooled box to produce an Ar with a constant working output.
Thermal spraying was performed with -N ₂ plasma under the conditions shown in Table 3.

The shape of the base material was 230 mm × 114 mm × 65 mm, and a triangular groove having a width of 20 mm and a depth of 10 mm was provided, and thermal spraying was performed so that the groove portion was overlaid.

After furnace cooling, the weight of each of the obtained constructions was measured, and the porosity of the constructions was measured with a porosimeter. The measurement results are shown in Table 3 together with the implementation conditions.

Further, for comparison, thermal spraying at room temperature (conventional example 16) and hot time (conventional example 17) by the conventional supply method using one supply pipe shown in FIG. 5 and two supply pipes are used. Thermal spraying at room temperature by the method (Comparative Example 18) was carried out under the operating conditions shown in Table 3, the adhesion weight of each obtained construction body was measured, and the porosity amount of the construction body was measured with a porosimeter. did. The measurement results are shown in Table 3 together with the implementation conditions. As a result, it was found that the adhesion rate was improved, and the porosity could be reduced even by hot working.

The measured adhesion weight is evaluated by the adhesion ratio, which is the weight ratio of the adhesion weight per unit time and the feed amount, and the porosity is 100 in the case of the conventional sprayed construction body with one supply pipe.
Was displayed as an index.

As is clear from Table 3, when the powder supply method according to the present invention is used for thermal spraying, the adhesion rate is 10 to 15 compared with the conventional method.
%, The porosity can be suppressed by about 10%, and it is clear that a film with excellent properties can be efficiently formed by thermal spraying. Therefore, the powder supply amount can be doubled to improve the construction efficiency.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view of a torch showing a supply method according to the invention. 2 and 3 are explanatory views of the torch nozzle portion showing the arrangement of the supply pipe according to the present invention. FIG. 4 is a side view of a torch showing a conventional supply pipe arrangement. 5 to 7 are longitudinal sectional front explanatory views of a torch showing a conventional supply method. FIG. 8 is a graph showing the relationship between the powder feed amount and the adhesion amount ratio, and FIG. 9 is a graph showing the relationship between the powder feed amount and the pore amount ratio. 1 ... Torch, 1 ... Nozzle, 3 ... Jet port, 4 ... Plasma frame central axis, 5,6 ... Supply tube, 7 ... Supply tube axis, 8 ... Plasma frame, 9 ... Substrate , 10,10a ……
Powder locus.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Kitani 5-15 Kitahama, Higashi-ku, Osaka City, Osaka Prefecture Sumitomo Metal Industries, Ltd. (56) References JP-A-55-111874 (JP, A)

Claims (1)

[Claims] 1. A plasma flame of a plasma spraying apparatus,
In a method of supplying a thermal spray material, which is made of a powder by a powder supply pipe having a powder supply pipe disposed outside, in one plasma flame of a plasma jet torch, 2
The number of the powder supply pipes is not less than 5 and not more than 5, and the center axis of each supply pipe intersects at one point of the plasma frame center axis on one plane orthogonal to the plasma frame center axis of the torch and the plasma frame center axis A method for supplying a thermal spray material, which is characterized in that the powders, which are gas-conveyed from respective supply pipes, are arranged at equal angles around each other and are jetted in a direction orthogonal to the central axis of the plasma frame, and collide with each other in the plasma frame. .