JPWO2017141925A1 - Cermet powder, protective coating member and method for producing the same, roll in electroplating bath and method for producing the same - Google Patents

Abstract

Provided is a cermet powder capable of producing a cermet film having both high wear resistance and high corrosion resistance against a strong acid having a pH of less than 1. The cermet powder of the present invention includes 40% by mass or more of tungsten carbide particles, 10 to 40% by mass of molybdenum carbide particles, and Ni or Ni alloy as a matrix metal, and further comprises chromium as a carbide or the matrix. It is characterized by containing 8% by mass or more as a metal or alloy element contained in the metal.

Description

  The present invention relates to a cermet powder, a protective film-coated member and a production method thereof, and a roll in an electroplating bath and a production method thereof.

  Conventionally, the following methods have been proposed as a method for producing a conductor roll used in an electroplating bath. In Patent Document 1, plasma arc spraying is performed in a low-pressure oxygen-free atmosphere using an alloy in which Co or Ni is the main component and Cr, C, Fe, Mo, or the like is added to the surface of a carbon steel roll. A method of manufacturing a conductor roll is described in which after the application, the film is melted again by plasma arc heating in the same atmosphere to form a non-porous sprayed film.

  In Patent Document 2, a spray coating layer is formed by spraying a mixed powder composed of carbide cermet powder and C-containing nickel chromium alloy powder on the surface of a roll body made of carbon steel, and then heating the spray coating layer. A method of manufacturing a conductor roll for electroplating is described, wherein the carbide is reprecipitated to form a reprecipitated carbide dispersion sprayed coating, and then the roll body is shrink-fitted into the outside of the roll base. ing.

  Patent Document 3 describes a conductor roll with improved corrosion resistance, in which a mixed powder composed of WC-Ni cermet and the remaining Ni-based self-fluxing alloy is sprayed on the surface of a roll made of SS400 and then remelted to form a coating layer. A manufacturing method is described.

  Patent Document 4 describes a conductor roll manufacturing method in which a self-fluxing alloy sprayed layer containing WC cermet is formed on the surface of a roll made of SS400, and further a WC cermet layer is formed thereon.

JP-A-1-198460 Japanese Patent Laid-Open No. 5-295592 JP 2002-88461 A JP 2006-183107 A

In Patent Document 1, under strong acid plating solution with a pH of less than 1, the plating solution infiltrates from the surface of the coating by continuous use, so the adhesion between the roll base material and the thermal spray coating decreases, and the coating peels off from the surface of the base material. There was a problem of falling. In fact, Patent Document 1 does not carry out in a severe environment where the pH is less than 1, and the implementation conditions are also shown only in a low current density range of ⁵ to 20 A / dm ² . Since the operation period is as short as 1000 hours, it has not been implemented for a long time, such as continuous operation for one month. Furthermore, since the coating is subjected to a thermal melting treatment after spraying, there is a problem that the manufacturing cost increases.

  Even in Patent Document 2, the plating solution infiltrates from the coating surface by continuous use under a strong acid plating solution having a pH of less than 1, so that the adhesion between the roll base material and the thermal spray coating is lowered, and the coating is peeled off from the base material surface. There was a problem of falling. Further, since the edge of the roll is acid-corroded by the plating solution, there is a problem that the yield of the product is lowered due to the fragments. In addition, it is necessary to remelt the roll after thermal spraying, and there is a problem that time and cost associated with roll regeneration including shrink fit insertion are increased.

  Even in Patent Document 3, the plating solution infiltrates from the surface of the coating under continuous use under a strong acid plating solution having a pH of less than 1. Therefore, the adhesion between the roll base material and the thermal spray coating decreases, and the coating peels off from the base material surface. There was a problem of falling. In addition, it is necessary to remelt the roll after thermal spraying, and there is a problem that time and cost associated with roll regeneration increase. Moreover, when it is going to apply this membrane | film | coat to a stainless steel roll, since a crack enters into a grain boundary by the heating of stainless steel by a remelting process, a roll will be damaged. For this reason, carbon steel having low corrosion resistance has to be used, and there has been a problem that fragments of acid-corroded carbon steel lower the product yield.

  Even in Patent Document 4, the plating solution infiltrates from the coating surface by continuous use under a strong acid plating solution having a pH of less than 1. Therefore, the adhesion between the roll base material and the thermal spray coating decreases, and the coating peels off from the base material surface. There was a problem of falling. Actually, in the acid corrosion test by immersion in the plating solution in Patent Document 4, the pH is 3.0, and the test under a severe environment where the pH is less than 1 is not performed. In addition, it is necessary to remelt the roll after thermal spraying, and there is a problem that time and cost associated with roll regeneration increase. Moreover, when it is going to apply this membrane | film | coat to a stainless steel roll, since a crack enters into a grain boundary by the heating of stainless steel by a remelting process, a roll will be damaged. For this reason, carbon steel having low corrosion resistance has to be used, and there is also a problem that the pieces of acid-corroded carbon steel reduce the product yield.

  As described above, the characteristics of conventional conductor rolls are that carbon steel is used as the roll material, and a NiCr alloy coating layer is applied to the roll surface to prevent reaction with the plating solution of the carbon steel. It is based on forming. The coating layer is characterized by containing a carbide (or cermet) mainly composed of WC for the purpose of preventing wear due to rubbing with the steel plate. As a result, it is possible to significantly reduce reaction and wear in an acidic plating bath with pH ≧ 1, and to ensure the roll life and reduce the defect rate.

  However, such a conventional conductor roll significantly increases the amount of acid corrosion of the carbon steel itself in a strong acid plating bath with pH <1, and the corrosion resistance of the coating layer itself containing carbide is insufficient. For this reason, there is a problem that the effect obtained for the large cost of roll production is small. That is, it has been difficult to achieve both high wear resistance and high corrosion resistance against strong acids having a pH of less than 1 with the rolls using the conventional technology and the surface treatment technology thereof.

  Furthermore, the conventional product with a sprayed coating on a carbon steel roll base material is damaged due to acid corrosion because the sprayed coating and the base material are damaged. It was found that non-defective products were generated and the product yield was lowered. Moreover, in a general electrotin plating process, it is known that tin ions in the plating solution change into metallic tin and cause an electrodeposition on the roll surface. Although this electrodeposited metal tin also causes defective products such as pressing irons, there is a problem that the tendency becomes prominent when the conventional roll is used.

  In view of the above problems, an object of the present invention is to provide a cermet powder capable of producing a cermet film having both high wear resistance and high corrosion resistance against a strong acid having a pH of less than 1. Another object of the present invention is to provide a protective film-coated member and a roll in an electroplating bath that have both high wear resistance and high corrosion resistance against a strong acid having a pH of less than 1, together with their production methods.

The gist configuration of the present invention for solving the above-described problems is as follows.
(1) 40% by mass or more of tungsten carbide particles,
10-40 mass% molybdenum carbide particles,
Ni or Ni alloy as matrix metal,
Including
The cermet powder further contains 8% by mass or more of chromium as a carbide or a metal or alloy element in the matrix metal.

  (2) The cermet powder according to (1) above, wherein the content of tungsten carbide particles is 70% by mass or less.

  (3) The cermet powder according to (1) or (2), wherein the tungsten carbide particles have a particle size range of 0.1 to 6 μm.

  (4) The cermet powder according to any one of (1) to (3), wherein a particle size range of the molybdenum carbide particles is in a range of 0.1 to 6 μm.

(5) A protective coating member having a stainless steel substrate and a cermet coating formed on the stainless steel substrate,
The cermet film is formed by dispersing tungsten carbide particles and molybdenum carbide particles in a matrix made of Ni or Ni alloy,
In the cermet film, the content of the tungsten carbide particles is 40% by mass or more, the content of the molybdenum carbide particles is 10 to 40% by mass, and further chromium as a carbide or a metal or alloy element in the matrix. A protective film-coated member containing at least mass%.

  (6) The protective film-coated member according to (5), wherein the content of tungsten carbide particles is 70% by mass or less.

  (7) The protective film-coated member according to (5) or (6), wherein a particle size range of the tungsten carbide particles is in a range of 0.1 to 6 μm in the cermet film.

  (8) The protective coating-coated member according to any one of (5) to (7), wherein a particle size range of the molybdenum carbide particles is in a range of 0.1 to 6 μm in the cermet coating.

  (9) The protective film-coated member according to any one of (5) to (8), wherein the cermet film has a surface roughness Ra of 0.5 to 10 μm.

  (10) A method for producing a protective coating-coated member, comprising a step of thermally spraying the cermet powder according to any one of (1) to (4) above onto a stainless steel substrate.

  (11) The said thermal spraying is a manufacturing method of the protective film coating | coated member as described in said (10) which is HVOF thermal spraying.

  (12) A roll in an electroplating bath comprising the protective film-coated member according to any one of (5) to (9) above.

  (13) The roll shaft part and the roll body part are both made of stainless steel, and only the roll body part is composed of the protective film-coated member according to any one of the above (5) to (9). A roll in an electroplating bath.

  (14) A cermet obtained by spraying the cermet powder according to any one of (1) to (4) above only on the roll body portion of a roll member in which the roll shaft portion and the roll body portion are both made of stainless steel. A method for producing a roll in an electroplating bath, wherein a film is formed.

  (15) The method for manufacturing a roll in an electroplating bath according to (14), wherein the thermal spraying is HVOF thermal spraying.

  According to the cermet powder of the present invention, it is possible to produce a cermet film that achieves both high wear resistance and high corrosion resistance against a strong acid having a pH of less than 1. Moreover, the protective film covering member and the roll in the electroplating bath of the present invention can achieve both high wear resistance and high corrosion resistance against strong acid having a pH of less than 1.

1 is a schematic cross-sectional view of a protective film covering member 100 according to an embodiment of the present invention. (A) is a schematic cross-sectional view of a conventional roll 200 in an electroplating bath, and (B) is a schematic cross-sectional view of a roll 300 in an electroplating bath according to an embodiment of the present invention.

(Cermet powder)
The cermet powder according to an embodiment of the present invention includes 40% by mass or more of tungsten carbide particles, 10 to 40% by mass of molybdenum carbide particles, and Ni or Ni alloy as a matrix metal, and further includes chromium as a carbide or the above-mentioned It is characterized by containing 8% by mass or more as a metal or alloy element contained in the matrix metal. According to this cermet powder, it is possible to produce a cermet film that has both high wear resistance and high corrosion resistance against strong acids with a pH of less than 1. Hereinafter, each element of the cermet powder of the present disclosure will be described.

  Tungsten carbide particles serve to impart high wear resistance and relatively high corrosion resistance to the cermet film. Examples of tungsten carbide particles include WC particles. The content of tungsten carbide particles needs to be 40% by mass or more. This is because if the amount is less than 40% by mass, sufficient wear resistance of the cermet film cannot be obtained. Further, the content of the tungsten carbide particles is preferably 70% by mass or less. This is because when the content exceeds 70% by mass, the content of other components becomes small, so that high corrosion resistance against strong acid having a pH of less than 1 cannot be obtained in the cermet film. From the viewpoint of reliably obtaining the effects of the present invention, the particle size range of the tungsten carbide particles is preferably in the range of 0.1 to 6 μm.

Molybdenum carbide particles are an important component in the present invention that plays a role of imparting not only high abrasion resistance to a cermet film but also high corrosion resistance against a strong acid having a pH of less than 1. Examples of molybdenum carbide particles include Mo ₂ C particles. The content of molybdenum carbide particles needs to be 10 to 40% by mass. If it is less than 10% by mass, high corrosion resistance to strong acid with a pH of less than 1 cannot be obtained in the cermet film. If it exceeds 40% by mass, the content of other components, particularly tungsten carbide particles, must be reduced. This is because sufficient wear resistance of the cermet film cannot be obtained. From the viewpoint of reliably obtaining the effects of the present invention, the particle size range of the molybdenum carbide particles is preferably in the range of 0.1 to 6 μm.

  The cermet powder of the present disclosure contains Ni or a Ni alloy as a matrix metal. Examples of the Ni alloy include NiCr-based alloys, NiCrMo-based alloys, and NiCoCrAlY-based alloys containing Ni as a main component. Ni as a matrix metal plays a role of imparting high corrosion resistance to a strong acid having a pH of less than 1 to the cermet film. From this viewpoint, the Ni content in the cermet powder is preferably 5% by mass or more. Moreover, it is preferable that Ni content in a cermet powder is 20 mass% or less from the relationship with suitable content of another component.

The cermet powder of this indication contains 8 mass% or more of chromium as a carbide or a metal or alloy element contained in the matrix metal. This chromium plays a role of imparting high corrosion resistance to a strong acid having a pH of less than 1 to the cermet film, and from this viewpoint, the content is required to be 8% by mass or more. From the relationship with the preferred content of other components, the chromium content in the cermet powder is preferably 20% by mass or less. Further, when the cermet powder of the present disclosure containing chromium carbide particles (Cr ₃ C ₂ particles), the effect from the standpoint of obtaining reliably the present invention, the particle size range is preferably in the range of 0.1～6Myuemu.

  The cermet powder of the present disclosure is preferably composed of the above components and inevitable impurities.

  In the cermet powder of the present disclosure, the molybdenum content is preferably not less than the chromium content from the viewpoint of imparting high corrosion resistance to a strong acid having a pH of less than 1 to the cermet coating.

  The production method of the cermet powder of the present disclosure is not particularly limited, and can be produced by a known or arbitrary method such as a melt pulverization method, a sintering pulverization method, or a granulation sintering method.

(Protective film covering member and method for producing the same, and roll in electroplating bath and method for producing the same)
Referring to FIG. 1, a protective film covering member 100 according to an embodiment of the present invention includes a stainless steel base material 10 and a cermet film 20 formed on the stainless steel base material. The cermet film 20 is formed by spraying the cermet powder of the present disclosure on the base material 10 as a thermal spray material. As a result, the cermet film 20 is in a state in which tungsten carbide particles and molybdenum carbide particles, and optionally carbide particles 24 containing chromium carbide are dispersed in a matrix 22 made of Ni or Ni alloy. Regarding the content and particle size range of tungsten carbide particles, the content and particle size range of molybdenum carbide particles, the Ni content, the chromium content, and the particle size range of the chromium carbide particles in the cermet coating 20, the cermet powder has been described. It is the same as that. In addition, a roll in an electroplating bath according to an embodiment of the present invention includes the protective film covering member 100. Such a protective coating-coated member and roll in an electroplating bath of the present disclosure can achieve both high wear resistance and high corrosion resistance against strong acid having a pH of less than 1.

  In particular, in the present embodiment, referring to FIG. 2 (B), the cermet powder of the present disclosure is provided only on the roll body 32 of a roll member in which the roll shaft 30 and the roll body 32 are both made of stainless steel. It is preferable to produce the roll 300 in the electroplating bath by spraying the cermet film 34 to form the cermet film 34.

  The protective film covering member of the present disclosure and the manufacturing method thereof, and the roll in an electroplating bath and the manufacturing method thereof have been completed based on the following knowledge of the present inventors.

As described above, in a strong acid plating bath having a pH <1, such as a methanesulfonic acid solution, the life and product yield are greatly reduced in the conventional roll. In order to elucidate this phenomenon and examine countermeasures, we focused on the electrochemical reaction that occurs on the roll in the plating solution. First, in the conductor roll in the plating bath, unlike the normal corrosion reaction, the corrosion reaction (anodic reaction) in which Fe (or Ni in the coating layer) is ionized and dissolved in the liquid on the surface, It is considered that a substitution reaction consisting of two main reactions, a reaction (cathode reaction) in which Sn ions in the solution are electrodeposited, proceeds. These reactions can be expressed as follows when the roll component is Fe and the plating component is Sn, for example.
The cathode ^{reaction: Sn 2+ + 2e - → Sn} (1)
Anode ^{reaction: Fe → Fe 2+ + 2e -} (2)

  The reactions of the above formulas (1) and (2) are electrochemically equivalent, and the total amount of electrons (e−) generated in the anode reaction is equal to the total amount of electrons consumed in the cathode reaction. On the surface of the conductor roll under such an electrochemical reaction environment, the dissolution reaction proceeds at a portion where the potential is locally increased (anode), and at the portion where the potential is locally decreased (cathode). The analysis reaction proceeds.

  The sites where these reactions occur can be considered to be uniformly distributed microscopically when the corrosion potential when the roll is immersed in the liquid is relatively high, and the corrosion is evenly distributed over the entire surface. As a result, the surface morphology can maintain the initial good state. However, under conditions where the plating solution is a strong acid with pH <1 or the plating current density is set too high, the site where the cathodic or anodic reaction occurs is fixed locally and the reaction proceeds. There are things to do. In such a case, the surface form changes greatly as described below, which may damage the plated product.

  First, regarding deposition of a plating component such as Sn by the cathode reaction, the reaction tends to concentrate at a site where the precipitation first occurs and grow as a metal. The grown metal deposit grows up to a certain size and then falls off due to a load such as rubbing with the steel plate, and the portion where the cathode reaction concentrates moves to another place. By repeating such a reaction, the plating metal such as Sn is deposited on the surface non-uniformly. At the same time, the dropped pieces of the plating metal may damage the surface of the product steel plate.

  In addition, when the anode reaction is fixed at a specific part and the reaction is concentrated, a specific element (such as Fe in the roll) constituting the part is selectively dissolved at the grain boundary, so that part of the roll surface or coating Part of the layer may fall off as fragments. Debris dropped from the surface may damage the surface of the product steel plate.

  That is, in the conventional roll described above, the corrosion potential is relatively lowered in a strong acid plating bath where the pH is <1 or when the current density is excessively high, and the microscopic uniformity of the anode and cathode distributions. Due to the destruction, the above-mentioned plating metal adheres and falls and the roll surface is partially broken due to local fixation, and as a result, the product yield may be lowered.

  Therefore, in order to ensure the roll life and maintain a high product yield even in a strong acid plating bath where the pH is <1 or when the current density is set high in order to increase the line speed, the reaction is simply performed. It is necessary to find a material that can prevent the phenomenon in which the reaction is concentrated as a result of locally fixing the site where the cathode reaction or the anode reaction proceeds as described above, without paying attention only to the amount. On the other hand, if such a material is used, it is possible to prevent the progress of the local corrosion as described above, and to secure the roll life and the product yield.

  Therefore, a static immersion test of the roll material was carried out in a tin plating solution using methanesulfonic acid having a pH of <1, and the change in corrosion potential with time was measured and the degree of substitution reaction was evaluated. As a result, when carbon steel was used as the roll material, the reaction amount was extremely high, and it was found that metal Sn was deposited at every part of the surface, and the deposited metal Sn mass repeated growth and detachment. In comparison, when stainless steel such as SUS316L was used as the roll material, the reaction amount was significantly low, and a thin reaction layer was formed on the surface, but no clear precipitation of metal Sn could be confirmed. Further, the reaction layer on the surface could be easily removed by washing with water and chemical washing, and precipitation of metal Sn could not be confirmed on the removed surface. In addition, when the corrosion potential at the time when 20 days passed after immersion was compared, it was found that stainless steel has a higher potential of 0.1 V or more than carbon steel and maintains a potential noble state.

  From these results, it was judged that stainless steel having a corrosion potential of about 0.1 V higher than that of carbon steel even in a strong acid solution with pH <1 has a small reaction amount and is less likely to cause immobilization of the anode and cathode on the surface. However, since the hardness of stainless steel is at most about HV200, there is a concern that the wear resistance against rubbing against the steel plate is low. Then, further examination was performed about the material of the coating layer for protecting stainless steel. As a material for protecting stainless steel, it is necessary to have high hardness and excellent wear resistance and to exhibit good corrosion resistance in a strong acid plating bath. As such a material, carbide cermet is promising, but it is known that good characteristics cannot be obtained with those described in Patent Documents 1 to 4. However, these carbide cermets were determined to have the potential to improve the electrochemical properties in the strong acid plating bath by adjusting the components, and were intensively studied.

In other words, a sample was prepared by using stainless steel as a base material and coating the surface with a dozen types of carbide cermet powders for thermal spraying, including those commercially available, by the HVOF thermal spraying method, and using a strong acid plating solution with pH <1.0. Immersion experiments were performed. As a result, it has been found that Ni or NiCr-based alloys are excellent for the cermet matrix, and that when the carbide contains Mo carbide rather than WC particles alone, good corrosion resistance can be obtained. Therefore, as a result of further research, in order to obtain high corrosion resistance in a strong acid solution, Cr is desirably contained in an amount of 8% by mass or more as a carbide or alloy element of the matrix, and the content of Mo contained as a carbide is It has been found that it is desirable that the content is at least equivalent to the Cr content. Moreover, Mo ₂ C is preferable as the Mo carbide, and even if the Mo content in the cermet is higher than the Cr content, the corrosion resistance is not impaired, but conversely the Mo content is higher than the Cr content. It has been found that desirable corrosion resistance is difficult to obtain when the amount is less than half.

  That is, as a carbide cermet film for protecting stainless steel from the substitution reaction as described above in a strong acid solution of pH <1, and for ensuring sufficient wear resistance against sliding action with a steel plate, Ni or Ni Tungsten carbide particles and molybdenum carbide particles are dispersed in a matrix made of an alloy. In the cermet film, the content of tungsten carbide particles is 40% by mass or more, and the content of molybdenum carbide particles is 10 to 40% by mass. Further, it is desirable to contain chromium in an amount of 8% by mass or more as a carbide or a metal or alloy element in the matrix. As the matrix mainly composed of Ni, good results were obtained with NiCr alloys, NiCrMo alloys, and NiCoCrAlY alloys.

  As a result of constant current anode / cathode polarization dissolution test of a test piece in which a carbide cermet film satisfying the above conditions was formed on stainless steel by HVOF spraying to form a protective film, the reaction layer was not formed, and The surface morphology was better than that of steel. In addition, as a result of measuring the corrosion potential, a potential higher by about 0.1 V than stainless steel was obtained. The above results indicate that the uniformity of the anode and cathode distribution formed on the surface of the carbide cermet coating formed by the above HVOF spraying is achieved at a finer level than stainless steel, and the reaction generation It was found that there was almost no concern that the steel plate would be damaged by objects. Thus, it has been found that it is possible to form a protective film exhibiting excellent corrosion resistance even in a strong acid plating bath while having excellent wear resistance.

  Here, it was confirmed that it is important to adjust the particle size of tungsten carbide particles and molybdenum carbide particles, which are the main components of the cermet, as a method for achieving both wear resistance and corrosion resistance in a trade-off relationship. That is, if a carbide having a particle size of less than 0.1 μm is used for the carbide which is the main component of cermet, the wear resistance is remarkably lowered, and if a particle having a particle size of 6 μm or more is used, the anode and cathode in the solution are used. There was a tendency that the microscopic uniformity of the distribution was not sufficiently maintained. It was confirmed that both wear resistance and corrosion resistance can be achieved when the particle sizes of tungsten carbide particles and molybdenum carbide particles are in the range of 0.1 to 6 μm.

  It was found that high-speed flame spraying methods such as HVOF and HVAF are desirable as a method for forming the protective film. For example, when comparing cermet coatings obtained by high-speed flame spraying methods such as HVOF and HVAF with cermet coatings obtained by plasma spraying and other thermal spraying methods, the porosity differs greatly, and high-speed HVOF, HVAF, etc. With a coating obtained by a thermal spraying method other than the flame, it was difficult to maintain a good surface state because the solution penetrated into the coating. In addition, when the film obtained to reduce the porosity is heat-treated at a high temperature, the carbides are decarburized to form lower carbides or form a reaction phase with the matrix component, and the wear resistance and corrosion resistance are remarkably high. It will decline. Such a tendency was also confirmed in a coating formed by welding overlay or cladding. That is, as a method for forming the carbide cermet film, a high-speed flame spraying method such as HVOF or HVAF is desirable.

  Even with protective coatings formed by high-speed flame spraying methods such as HVOF and HVAF, if the surface roughness Ra exceeds 10 μm, the probability of scratching the steel plate with carbide projections increases, and Ra When the thickness was less than 0.5 μm, it was found that the surface condition of the steel sheet was impaired as a result of insufficient frictional force and rolling of the roll on the steel sheet. Accordingly, the surface roughness Ra of the carbide cermet film is preferably 0.5 to 10 μm.

<Example 1>
Samples of conventional roll specifications and roll specifications according to the present invention were prepared and immersed for 20 days in a strong acid plating solution (methanesulfonic acid 50 g / L, tin ion concentration 25 g / L) adjusted to pH <1 A test was conducted. Five types of samples shown in Table 1 were produced. That is, No. 1 is a conventional carbon steel base material, and the protective film is also a conventional sample. On the other hand, in the samples Nos. 2 to 5, the base material was stainless steel. As for the protective coating, No. 2 uses the same conventional coating as No. 1, and No. 3 to No. 5 use various carbide cermet HVOF coatings with a matrix of Ni or Ni-based alloy. No. 5 corresponds to the cermet specification of the present invention. In the film No. 5, the Mo content is 9.4% by mass, the Cr content is 8.7% by mass, the WC particles have a minimum particle size of 0.1 μm and a maximum of 6 μm, and the Mo ₂ C particles have a minimum particle size of 0.1 μm. The maximum was 6 μm, and the surface roughness Ra was 3.0 μm. Each sample was prepared so that the exposed portion of the substrate and the protective coating portion had approximately the same surface area, and the characteristics of the joint portion between the coating and the substrate could be evaluated.

In order to evaluate the corrosion resistance of the protective film, the mass change (corrosion loss) of the sample before and after immersion was measured, and the results are shown in Table 1. In addition to this mass change, Table 1 shows the result of observing the surface of the protective film after immersion for 20 days with an electron microscope and the measured value of the corrosion potential. In addition, the results of the Suga abrasion test (# 120-SiC paper, load 3.25 kgf, 400 reciprocations) conducted separately are also shown. The film observation results were evaluated according to the following criteria.
◎: Almost no change ○: Slight change △: Change x: Large change

  As is clear from the results shown in Table 1, in the plating solution with pH <1, the mass change is large in the conventional specification sample Nos. 1 to 4, especially the sample No. 1 based on carbon steel. It turns out that a form also worsens. Furthermore, in the conventional specification sample using carbon steel as a base material, the boundary between the coating and the base material was largely destroyed by corrosion. Compared to this, it can be seen that the sample in which stainless steel is protected with a cermet film not only has a small mass change but also hardly deteriorates the surface morphology. In particular, Sample No. 5, which is an example of the present invention, had a very good surface morphology as compared with others. This also corresponds to the measurement result of the corrosion potential (the highest among the measurement samples), and confirms that the uniformity of the anode and cathode distribution on the coating surface is excellent. Moreover, it turns out that the example of this invention is excellent also at the point of abrasion resistance.

<Example 2>
Focusing on the blending ratio of the protective film of No. 5 specification shown in Example 1, WC particles containing Ni or Ni-20Cr alloy as a matrix and having a particle size adjusted to a range of 0.1 to 6 μm, Cr ₃ C ₂ Various cermet powders containing particles and Mo ₂ C particles were prepared. The cermet powder obtained on stainless steel was HVOF sprayed to form a protective coating. Table 2 shows the film composition of each sample. While performing the immersion test similar to Example 1, the Suga abrasion test was implemented. The evaluation results are shown in Table 2.

As is apparent from the results shown in Table 2, it is effective to add a large amount of Mo ₂ C particles if the corrosion resistance to the plating solution is to be improved, and a large amount of WC particles is added to improve the wear resistance. It is effective. And in No.4-11 which is an example of this invention, it turns out that high abrasion resistance and the high corrosion resistance with respect to the strong acid from which pH is less than 1 are compatible.

  In addition, in the sample in which the cermet powder described in the present example was a protective coating by the atmospheric plasma spraying method, the porosity is high, and the influence of the alteration of the carbide is strong, and regarding corrosion resistance and wear resistance, The properties as good as those of the coating prepared by HVOF spraying were not obtained.

<Example 3>
An example in which a conventional product and the present invention product are applied to a conductor roll of an electroplating line will be described. 2A and 2B show a comparison between the structure of a conventional roll and the structure of a roll according to the present invention. In the conventional roll shown in FIG. 2 (A), a carbon steel sleeve is formed by heat-spraying a carbon steel sleeve while a carbon steel tube is heat-fitted to a copper shaft core to form a shaft portion. The body part was configured by shrink fitting to the part, and these were combined to form a roll body. On the other hand, in the present invention shown in FIG. 2 (B), it is only necessary to form a thermal spray coating on the roll body made of stainless steel, and it can be seen that the production of the roll body is extremely easy. The specification of the film according to the present invention was No. 6 in Example 2.

  In addition, when the heat generation by energization of each roll was measured with a thermoviewer, both were 0.14 to 0.16 ° C./min, and it was confirmed that the level was satisfactory for operability. The composition of the plating bath is the same as in Example 1. The roll pressing pressure on the steel plate was 0.2 MPa, and the plate passing speed was 150 to 490 m / min. The number of days used is 230 days. After the use was completed, each roll was pulled up from the bath, and the surface roughness of the threaded plate portion and the Sn adhesion amount were investigated. The results are shown in Table 3.

  From the results shown in Table 3, the surface roughness of the threaded part of the conventional roll decreased from Ra3.0 μm before use to Ra0.81 μm, close to 1/4, whereas with the roll to which the present invention was applied, after use. Ra1.0μm or more was maintained, and it was confirmed that the film life was improved by 30% or more compared to the conventional roll. It can also be seen that the Sn adhesion amount is reduced by about 10% in the roll of the present invention compared to the conventional roll. Both of these results show that the corrosion resistance to the plating solution and the wear resistance to the steel sheet can be improved in the specification of the present invention. In fact, the failure rate of the products obtained using each roll was as high as 2.37% with the conventional roll, whereas the roll of the present invention succeeded in reducing it to 0.43% with 1/5 or less. This is presumably because the rate of occurrence of coating damage and coarse electrodeposited Sn debris, which are the cause of pressing creases, was significantly reduced by improving corrosion resistance.

  In addition, from the results of the same actual machine operation, it is also understood that the roll usage limit is about Ra 0.5μm surface roughness, and if the initial surface roughness exceeds Ra 10μm, the frequency of generating scratches on the product increases. ing. Therefore, the surface roughness of the cermet coating according to the present invention is preferably Ra 0.5 to 10 μm.

  The cermet powder of the present invention can be suitably used as a material for a protective film (cermet film) in a protective film coating member such as a roll in an electroplating bath. The roll in the electroplating bath of the present invention can be suitably used, for example, as a conductor roll in a strong acid electroplating bath having a pH of less than 1.

100 Protective film covering member 10 Base material (stainless steel)
20 Cermet coating 22 Matrix 24 Carbide particles (WC particles, Mo ₂ C particles, optionally Cr ₃ C ₂ particles)
300 Roll in electroplating bath 30 Roll shaft part 32 Roll body part 34 Cermet coating (thermal spray coating)

Claims (15)

40% by weight or more of tungsten carbide particles,
10-40 mass% molybdenum carbide particles,
Ni or Ni alloy as matrix metal,
Including
The cermet powder further contains 8% by mass or more of chromium as a carbide or a metal or alloy element contained in the matrix metal.   The cermet powder according to claim 1, wherein the content of tungsten carbide particles is 70% by mass or less.   The cermet powder according to claim 1 or 2, wherein a particle size range of the tungsten carbide particles is in a range of 0.1 to 6 µm.   The cermet powder as described in any one of Claims 1-3 whose particle size range of the said molybdenum carbide particle exists in the range of 0.1-6 micrometers. A protective coating member having a stainless steel substrate and a cermet coating formed on the stainless steel substrate,
The cermet film is formed by dispersing tungsten carbide particles and molybdenum carbide particles in a matrix made of Ni or Ni alloy,
In the cermet film, the content of the tungsten carbide particles is 40% by mass or more, the content of the molybdenum carbide particles is 10 to 40% by mass, and further chromium as a carbide or a metal or alloy element in the matrix. A protective film-coated member containing at least mass%.   The protective film-coated member according to claim 5, wherein the content of tungsten carbide particles is 70% by mass or less.   The protective coating-coated member according to claim 5 or 6, wherein a particle size range of the tungsten carbide particles is in a range of 0.1 to 6 µm in the cermet coating.   The protective film covering member according to any one of claims 5 to 7, wherein a particle size range of the molybdenum carbide particles in the cermet film is in a range of 0.1 to 6 µm.   The protective film covering member according to any one of claims 5 to 8, wherein the cermet film has a surface roughness Ra of 0.5 to 10 µm.   The manufacturing method of a protective film coating | coated member including the process of thermally spraying the cermet powder as described in any one of Claims 1-4 on a stainless steel base material.   The said thermal spraying is a manufacturing method of the protective film coating | coated member of Claim 10 which is HVOF thermal spraying.   The roll in an electroplating bath characterized by including the protective film coating | coated member as described in any one of Claims 5-9.   In an electroplating bath, the roll shaft portion and the roll body portion are both made of stainless steel, and only the roll body portion is composed of the protective film-coated member according to any one of claims 5 to 9. roll.   A cermet film is formed by spraying the cermet powder according to any one of claims 1 to 4 only on the roll body part of a roll member made of stainless steel, both of the roll shaft part and the roll body part. A method for producing a roll in an electroplating bath.   The said thermal spraying is a manufacturing method of the roll in an electroplating bath of Claim 14 which is HVOF thermal spraying.

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