WO2019202720A1

WO2019202720A1 - Nozzle for cold spray and cold-splay device

Info

Publication number: WO2019202720A1
Application number: PCT/JP2018/016234
Authority: WO
Inventors: 和真高橋; 佳弘細谷; 弘之吉見
Original assignee: 株式会社特殊金属エクセル
Priority date: 2018-04-20
Filing date: 2018-04-20
Publication date: 2019-10-24
Also published as: JP6404532B1; JPWO2019202720A1

Abstract

[Problem] To provide a nozzle for cold spray and a cold-spay device that prevent clogging due to adhesion of powder materials to an inner wall part of the nozzle for cold spray and that has a nozzle which is not abraded even when high-hardness powder materials are used. [Solution] The nozzle for cold spray for spraying powder materials according to the present invention comprises a reduced part 1, a throat part 2, an enlarged part 3 widen toward an end, and a nozzle body 12 in which a powder-material charging port 4 is formed. The nozzle body 12 is constituted by a material of a metal or an alloy having cohesive energy of 170 kcal/ g-atom or more. The cold-spay device is a device for performing cold spraying with use of the nozzle for cold spray constituted as described above.

Description

Nozzle for cold spray and cold spray device

The present invention relates to a nozzle suitable for use in cold spray and a cold spray apparatus equipped with the nozzle.

The cold spray method is a technique in which a powder material (metal powder) is collided with a base material in a solid phase state below the melting temperature to form a film on the base material. This is essentially different from the thermal spraying method in which the material is melted and adhered to the substrate.
The cold spray method provides a dense film that does not oxidize in the atmosphere, has little thermal effect on the material particles, suppresses thermal alteration, has a high film formation rate, can be thickened, and has high adhesion efficiency Etc., and has excellent advantages that cannot be obtained by thermal spraying.
For this reason, attention has been focused on effectively applying the metal material on which this film is formed to various structural materials.

On the other hand, the conventional cold spray method has a problem in that the powder material adheres to the inner wall portion of the nozzle due to the material of the nozzle and the powder material to be used. In particular, when the spraying temperature is higher than 500 ° C in order to increase the adhesion efficiency, the temperature of the inner wall of the nozzle rises, and the interatomic bonding between the powder material and the nozzle material easily proceeds to the nozzle. The adhesion of becomes faster.
For example, Fig. 3 (a) shows the internal state of the nozzle when stainless steel is used as the nozzle material and maraging steel is used as the powder material, and the nozzle is continuously operated for 120 minutes at a spraying pressure of 3.0 MPa and a spraying temperature of 800 ° C. Show. In FIG. 3 (a), the broken line portion indicates the location where the powder material is adhered, but it has been confirmed that 15% of the cross-sectional area is blocked.
As described above, in the conventional cold spray method, the nozzle is blocked in a short time, and therefore, the nozzle needs to be frequently replaced. As a result, this has been an obstacle to the practical application of the continuous coating method that requires operation for 300 minutes or more.
Hereinafter, known documents referring to the cold spray method and the thermal spraying method will be described.

Patent Document 1 describes that the portion of the nozzle inner wall surface on which particle adhesion is likely to occur can be effectively prevented by adhering the raw material powder by configuring it with either quartz glass or borosilicate glass. Glass materials have a problem that wear progresses due to the spraying of high hardness powder material such as maraging steel. For example, Fig. 3 (b) shows a state in which maraging steel is used as a powder material, and a quartz glass tube having an outer diameter of φ8 and an inner diameter of φ6 is continuously operated for 15 minutes at a spraying pressure of 3.0 MPa and a spraying temperature of 800 ° C. It has been confirmed that as much as 40% of wear occurs per volume.

In Patent Document 1, the entire divergent part is made of borosilicate glass, and using Inconel powder material, the operating gas temperature is 800 ° C, the powder supply rate is 200 g / min, and the chamber gas pressure is 3 MPa. Although an example of operation is disclosed, the evaluation relates to the observation of the turbulence of the jet flow of the powder material, the confirmation of the powder material adhesion on the inner wall of the nozzle and the film formation efficiency, and the degree of wear of the nozzle is not disclosed .

In Patent Document 2, although it is a nozzle for a thermal spray gun, it is possible to control the plasma / arc adhesion region by the dynamic influence of heat by configuring the nozzle surface portion with any of tungsten, molybdenum, silver or iridium. It is disclosed. However, while the cold spray method causes the powder material to collide with the base material in the solid state below the melting temperature, the spraying method melts the material to be sprayed and attaches it to the base material. The occurrence of this proceeds by a completely different mechanism.

For example, high-speed flame spraying and plasma spraying can be cited as spraying methods that operate in the supersonic region as in the cold spray method. In high-speed flame spraying, the inner wall surface on the outlet side of the nozzle tends to be clogged, but the cause is that the powder material that has entered the high-speed frame is pulverized and refined, resulting in extremely poor fluidity. In such a case, measures such as lowering the combustion chamber pressure, increasing the particle size of the powder material, shortening the nozzle length, and lowering the supply amount of the powder material are effective.

In plasma spraying, charge concentration occurs due to wear on the inner wall surface of the nozzle and adhesion to an anode material such as copper occurs. However, as disclosed in Patent Document 2, wear due to direct contact with a plasma arc is caused. This can be prevented by using a high-melting-point material with a melting point of 1900 ° C or higher, such as tungsten or molybdenum, which can withstand heat, or a high thermal conductivity material, such as silver, as the lining material.
However, as already described, the plasma spraying and the cold spray according to the present invention have completely different film forming mechanisms, and the problem of the present invention cannot be solved by applying the plasma spraying technique.

Patent Document 3 discloses a method of preventing nozzle blockage by forming a part or all of a divergent portion, which is an enlarged portion of a nozzle, with a glass material. In addition, in the reduced portion and the throat portion of the nozzle, the replacement work efficiency of the divergent portion is increased by using different materials such as metal and heat-resistant resin. However, as described in Patent Document 3, a combination of members having a difference in linear expansion coefficient may cause voids due to non-uniform thermal diffusion on the joint surface in addition to interface peeling due to thermal shock.

In Patent Document 4, tungsten carbide is used for the linear convergence nozzle of the micro cold spray direct writing system. Nozzle molding of tungsten carbide has a feature that the finished surface roughness is rough because a sintering method is common. Therefore, after sintering, it is necessary to smooth the inside of the nozzle by machining such as surface polishing. However, since tungsten carbide is a carbide, its workability is very poor, and it is difficult to satisfy the required dimensional accuracy within ± 2.0 μm inside the sonic nozzle.

WO2012 / 086037 WO2014 / 120357 WO2012 / 086037 Special table 2015-511270

As described above, when a glass material is used to prevent adhesion of the powder material, there is a problem that the wear of the nozzle proceeds due to the spraying of the powder material with high hardness. For example, maraging steel with a Vickers hardness exceeding HV300, and powder materials with high hardness such as tungsten and molybdenum further accelerate the wear of the nozzle. When the wear of the nozzle is promoted, shock waves are generated by forming irregularities on the inner wall portion of the nozzle, so that the flow of the powder material becomes non-uniform. As a result, the position where the powder material forms the film on the base material is disturbed, and there is a problem in that the film thickness varies due to the deterioration of location accuracy.

The present invention has been made in view of the above circumstances, and as a nozzle material, a cold spray that prevents clogging due to adhesion of the powder material to the inner wall of the nozzle and prevents the nozzle from being worn even when a high-hardness powder material is used. An object is to provide a nozzle and a cold spray device.

In order to solve the above-mentioned problems, the present inventors have conducted intensive research, and the powder material does not adhere to the inner wall of the nozzle even when a long-time cold spray is performed. In order to obtain a manufacturing method that does not wear, it has been found that the design of the material and shape of the nozzle is particularly important as will be described later.

First, the present inventors use a metal having a cohesive energy of 170 kcal / g-atom or more and an alloy thereof as the nozzle material, so that the powder material can be applied to the nozzle inner wall even when cold spray is performed for a long time. It has been found that the nozzle does not wear even when a high hardness powder material is not used. In other words, the reason why the powder material does not adhere to the nozzle is that the metal with higher cohesive energy, which is the force for separating the constituent atoms of the solid, is more stable as a solid, and the interatomic bond between the powder material and the nozzle material is less likely to occur. Can be mentioned. FIG. 4 is a graph showing the relationship between each period and the cohesive energy in the periodic table. Further, the cause of the nozzle not being worn is that the nozzle material has characteristics of a high melting point and a high hardness.

In particular, when the spraying temperature is higher than 500 ° C. in order to increase the adhesion efficiency, the temperature of the inner wall surface of the nozzle rises, and the higher the temperature, the more brittle the nozzle material becomes and the more easily it is worn. Metals with high cohesive energy are characterized by having a high melting point of 1900 ° C. or higher and are not easily embrittled at high temperatures. In addition, by selecting a material of HV150 or higher for the nozzle, it is possible to further prevent nozzle wear.
For example, tantalum has a hardness of HV220, tungsten has a hardness of HV350, and osmium has a high hardness of HV410 and is hard to wear. However, vanadium of HV120 and the like is easily worn.

In addition, although tungsten is disclosed in the nozzle for a thermal spray gun in Patent Document 2, the purpose of this document is to use a high melting point material that can withstand direct contact with a plasma arc. However, the cold spray method is not limited to this, and molybdenum and iridium, which are high melting point materials disclosed in Patent Document 2, cannot be used because the cohesive energy is less than 170 kcal / mol. About each cohesive energy, molybdenum is 155 kcal / mol and iridium is 165 kcal / mol.

For example, FIG. 3 (c) shows the internal state of the nozzle when operated continuously for 120 minutes at a spraying pressure of 3.0 MPa and a spraying temperature of 800 ° C. using molybdenum as the nozzle material and maraging steel as the powder material. However, it has been confirmed that a blockage of 5% occurs in the cross-sectional area. Thus, even if it is a high melting point material, when the cohesive energy is less than 170 kcal / mol, it can be said that an interatomic bond between the powder material and the nozzle material occurs and is likely to adhere.

The present invention has been made by integrating the above findings and has the following configuration.
[1] Nozzle inlet portion to which gas for accelerating powder material and heating powder material is supplied, a nozzle reduction portion following this nozzle inlet portion, a divergent nozzle enlargement portion following this nozzle reduction portion, and this nozzle A powder material inlet provided in the enlarged portion, and a powder material charged from the powder material inlet and heated below the melting point of the powder material by the gas is conveyed to the gas, and the substrate is supersonic. A nozzle for cold spray formed with a nozzle outlet part sprayed on
The nozzle is made of a metal or an alloy having a cohesive energy of 170 kcal / g-atom or more, and a nozzle for cold spraying.
[2] The cold spray nozzle according to [1], wherein the metal or alloy having a cohesive energy of 170 kcal / g-atom is a metal selected from the group of niobium, tantalum, and tungsten or an alloy thereof.
[3] The nozzle for cold spray according to [1] or [2], wherein the metal or alloy constituting the nozzle has a melting point of 1900 ° C. or higher.
[4] The cold spray nozzle according to any one of [1] to [3], wherein the metal or alloy constituting the nozzle has a hardness of HV150 or higher.
[5] The nozzle for cold spray according to any one of [1] to [4], wherein the nozzle has an integral nozzle structure.
[6] The cold spray nozzle described in any one of [1] to [5], means for supplying the gas for accelerating the powder material and heating the powder material into the nozzle from the nozzle inlet, and the powder material A cold spray device comprising means for supplying the powder material into the nozzle from the inlet.

According to the present invention, by using a metal or alloy having a cohesive energy of 170 kcal / g-atom or more as a material for a nozzle, it is possible to prevent the powder material from adhering to the inner wall of the nozzle and to have a high hardness. Can be used to produce a cold spray coating without wear on the nozzle. As a result, it is possible to produce a continuous coating that requires 300 minutes or more of operation for all powder materials regardless of hardness. The film position accuracy can be obtained.

Moreover, since the material of the nozzle is not tungsten carbide but a metal or an alloy as in the invention of Patent Document 4, the moldability is good and the inside of the nozzle can be made smooth.
Furthermore, since it is possible to configure the nozzle integrally using the same material metal or alloy, it is not necessary to combine members having a difference in linear expansion coefficient as in the invention described in Patent Document 3, As a result, voids are not generated due to interfacial debonding due to thermal shock and non-uniform thermal diffusion of the joint surface.

FIG. 1 is a schematic sectional view showing an example of a main body portion of a cold spray nozzle according to the present invention. FIG. 2 is an explanatory diagram showing an overall outline of the cold spray apparatus. FIG. 3 is a photograph showing the internal state of the nozzle when continuously operated using a nozzle made of a material that does not fall within the scope of the present invention. FIG. 3A shows the internal state of the nozzle when continuously operating for 120 minutes at a spraying pressure of 3.0 MPa and a spraying temperature of 800 ° C. using stainless steel as the nozzle material and maraging steel as the powder material. The photo, Fig. 3 (b) shows the state when maraging steel is used as the powder material and the quartz glass tube with an outer diameter of φ8 and an inner diameter of φ6 is continuously operated for 15 minutes at a spraying pressure of 3.0 MPa and a spraying temperature of 800 ° C. Fig. 3 (c) shows the inside of the nozzle when operated continuously for 120 minutes at a spraying pressure of 3.0 MPa and a spraying temperature of 800 ° C, using molybdenum as the nozzle material and maraging steel as the powder material. It is a photograph showing the state. FIG. 4 is a graph showing the relationship between each period in the periodic table and the cohesive energy, and the solid line with the highest peak indicates the sixth period in the periodic table. This table is quoted from 2006/10 literature, the origin of manufacturing – the world of science vol30 “Iron in metal”. FIG. 5 shows a rewinding device that sprays a powder material onto the center of the width of the base material while winding the base material.

First, the form of the nozzle according to the present invention will be described based on the sectional view of the nozzle body shown in FIG. In FIG. 1, the nozzle body continues through a reduction part 1 following a nozzle inlet part 11 a to which acceleration gas (flow direction is indicated by an arrow) is supplied, and a throat part 2 (minimum reduction part) to the reduction part 1. It is comprised from the elongate wide end expansion part 3 and the nozzle exit part 11b. The nozzle according to the present invention only needs to include the reduced portion 1, the throat portion 2, and the enlarged portion 3 between the nozzle inlet portion 11a and the nozzle outlet portion 11b, and other shapes are arbitrary. For example, in addition to the conical shape, the enlarged portion 3 may be a quadrangular pyramid divergent shape, and a parallel portion may be provided on the nozzle outlet side from the enlarged portion 3.
The enlarged portion 3 is provided with a powder inlet 4 into which a powder material is charged. The powder inlet 4 is preferably located close to the throat portion 2 in the enlarged portion 3.
Note that the cold spray nozzle (nozzle body) shown in FIG. 1 is an example in which one powder inlet 4 is provided, but a plurality of nozzles may be provided as necessary. For example, when mixing different powder materials, the powder materials may be supplied from a plurality of powder inlets 4 using a required number of powder supply devices.

In the present invention, all of the reduced portion 1, the throat portion 2 and the enlarged portion 3 are formed of a metal or alloy having a cohesive energy of 170 kcal / g-atom or more, and as a result, adhesion and wear of the nozzle inner wall portion are prevented. be able to.
As long as the metal or alloy constituting the nozzle has the above cohesive energy, the nozzle body may be configured by combining a plurality of metals or alloys. Therefore, it is preferable to limit the dimensional accuracy to any one of them.

The method for producing the nozzle is not particularly limited, but machining by a machine tool such as machining, machining by a press, or the like is common.
In addition, the nozzle body may be manufactured by combining a plurality of members, but it is preferable that the entire nozzle is an integral type because there is a possibility that a gap is generated due to non-uniform thermal diffusion of the joint surface.

The material of the nozzle (nozzle body) is selected from tungsten, tantalum, rhenium, hafnium, niobium and alloys thereof having a cohesive energy of 170 kcal / g-atom or more. Niobium is preferred. As the alloy, an alloy such as tungsten-niobium, tantalum-tungsten, or tantalum-niobium is preferable because it is easily dissolved.

Examples of the accelerating gas include air, nitrogen, helium, argon, or a mixture thereof. Copper and other materials that easily oxidize powder can improve the adhesion efficiency by using helium as an acceleration gas, so an appropriate acceleration gas can be selected depending on the powder material and the material of the substrate to be laminated. preferable.

FIG. 2 is an overall schematic diagram of the cold spray apparatus according to the present invention. The accelerating gas is supplied in the order of the compression cylinder 5 and the transport pipe 6, and is heated by a heater 7 provided in the transport pipe as necessary. Since the heating temperature increases the adhesion efficiency as the temperature increases, the lower limit is preferably 100 ° C. or higher and the upper limit is preferably within the range of the melting point of the material powder used.

The powder material is supplied in the order of the powder supply device 8 and the transport pipe 9, but when mixing a plurality of powder materials, it is necessary to prepare the necessary number of powder supply devices.

The powder material supplied from the powder inlet 4 is ejected from the nozzle outlet 11 in a state where the acceleration gas transported into the chamber 10 passes through the nozzle throat 2 and is accelerated at supersonic speed. The “supersonic speed” is a speed higher than the sound speed of 1225 km / h, and the upper limit of operation in the present invention is 3960 km / h.

Next, examples of the present invention will be described together with comparative examples that deviate from the conditions of the present invention.
Using the nozzle material (nozzle body material) shown in Table 1 and the powder material shown in Table 2, the nozzle inner diameter is 5mm, the operating pressure is 3MPa, the spraying temperature is 800 ℃, the acceleration gas is The system was operated for 300 minutes with the nitrogen and powder feed rates set at 200 g / min. The base material and the film formation method to form a film by spraying use a pure nickel coil of thickness 0.5mm, width 50mm, length 400m or more in order to evaluate the operation for 300 minutes and the film position accuracy. As shown in FIG. 2, the powder material was sprayed on the center of the width of the base material while winding the base material with a rewinding device. In FIG. 5, reference numeral 12 denotes a nozzle body, and 13 denotes a rewinding device.
Table 3 shows the evaluation results of nozzle clogging, adhesion efficiency, and location accuracy with respect to the stacking conditions.

(Evaluation of nozzle blockage)
Evaluation of nozzle clogging is when the inner wall of the nozzle is observed after 300 minutes of operation, and the case where adhesion of the material powder is not confirmed is set to “Yes”, and the powder material does not come out due to clogging during 300 minutes of operation. Was rejected as “x”.

(Evaluation of adhesion efficiency)
For the evaluation of the adhesion efficiency, calculate the adhesion rate from the weight of the powder material before spraying and the powder material adhered to the pure nickel coil after spraying. If it was less than that, it was judged as “failed”.

(Evaluation of coating position accuracy)
The film position accuracy was evaluated by measuring the stacking position and stacking width of the central part of the pure nickel base material at the time when the length of 1 meter elapsed after the start of spraying and when the length of 1 meter after the end of spraying was measured. A case where the difference in the stacking position or stacking width was 0.5 mm or less was evaluated as “good”, and a case where it exceeded 0.5 mm was determined as “failed”.

Table 1

Table 2

Table 3

(Example)
In Table 3, it was confirmed that the inventive examples (Nos. 1 to 3) were excellent in adhesion efficiency and film position accuracy even when a powder material exceeding HV300 was used, and the nozzle was not blocked even after 300 hours of operation.

(Comparative example)
On the other hand, Comparative Examples: Nos. 4 to 6 had a problem that the nozzles were blocked before reaching 300 hours of operation and the powder material could not be sprayed.
Comparative Examples: Nos. 7 to 9 caused wear on the inner wall of the nozzle when material powder exceeding HV300 was used, and could not satisfy the adhesion efficiency and the film position accuracy.
Comparative Example: Nos. 10 to 11 had nozzle melting when the spraying temperature reached the glass transition temperature of each material.

As can be seen from the above experimental results, according to the present invention, the metal or alloy having a cohesive energy of 170 kcal / g-atom or more is used as the material of the nozzle body, so that the powder material adheres to the inner wall of the nozzle. In addition, the nozzle is not worn even when a powder material with high hardness is used, and continuous coating production requiring operation for 300 minutes or more can be performed and high film position accuracy can be obtained.

DESCRIPTION OF SYMBOLS 1 ... Reduction part 2 ... Throat part 3 ... Expansion part 4 ... Powder material injection port 5 ... Compression cylinder 6 ... Conveyance pipe 7 ... Heater 8 ... Powder supply apparatus 9 ... Transport pipe 10 ... Chamber 11a ... Nozzle inlet 11b ... Nozzle outlet 12 ... Nozzle body 13 ... Rewinding device

Claims

A nozzle inlet for supplying a gas for accelerating powder material and heating powder material to the nozzle body, a nozzle reducing part following the nozzle inlet, a divergent nozzle expanding part following the nozzle reducing part, and the nozzle A powder material inlet provided in the enlarged portion, and a powder material charged from the powder material inlet, transported in the nozzle body by the gas, and heated below the melting point of the powder material are supersonic. A nozzle for cold spray formed with a nozzle outlet part sprayed on the base material,
The nozzle body is made of a metal or an alloy having a cohesive energy of 170 kcal / g-atom or more, and a nozzle for cold spraying.
The cold spray nozzle according to claim 1, wherein the metal or alloy having a cohesive energy of 170 kcal / g-atom is a metal selected from the group of niobium, tantalum, and tungsten, or an alloy thereof.
The nozzle for cold spray according to claim 1 or 2, wherein the melting point of the metal or alloy constituting the nozzle body is 1900 ° C or higher.
The cold spray nozzle according to any one of claims 1 to 3, wherein the metal or alloy constituting the nozzle body has a hardness of HV150 or more.
The cold spray nozzle according to any one of claims 1 to 4, wherein the nozzle body has an integral nozzle structure.
A nozzle for cold spray according to any one of claims 1 to 5, means for supplying gas for accelerating the powder material and heating the powder material into the nozzle from a nozzle inlet, and supplying the powder material to the powder A cold spray device comprising means for supplying the material into the nozzle from the material inlet.