TW201734223A - Cermet powder, protective film-coated member and method for producing same, and electroplating-bath roll and method for producing same - Google Patents

Abstract

Provided is a cermet powder able to produce a cermet film which exhibits high abrasion resistance and high resistance to strong acids having pH values of less than 1. This cermet powder is characterized by containing 40 mass% or more of tungsten carbide particles, 10-40 mass% of molybdenum carbide particles, and Ni or a Ni alloy as a matrix metal, and further containing 8 mass% or more of chromium as a metal or alloy element contained in the carbides or the matrix metal.

Description

Cermet powder, protective film covering member, manufacturing method thereof, and electroplating bath and manufacturing method thereof

The present invention relates to a cermet powder, a protective film covering member, a method for producing the same, a roll in an electroplating bath, and a method for producing the same.

Conventionally, as a method of producing a conductive roller used in an electroplating bath, the following is proposed. Patent Document 1 discloses a method for producing a conductive roller, which is based on a surface of a carbon steel roll, and an alloy containing Cr, C, Fe, Mo or the like as a main component and having Co or Ni as a main component is used as a spray material. After the plasma arc spraying is performed in a low pressure oxygen-free environment, the film is heated by the plasma arc heating in the same environment to form a non-porous molten film.

Patent Document 2 describes a method for producing a conductive roller for electroplating, characterized in that a mixed powder containing a carbide cermet powder and a nickel-chromium alloy powder containing C is formed on a surface of a carbon steel roll main body portion. After the coating layer is sprayed, the molten coating layer is heated to re-precipitate the carbide to form a re-precipitated carbide-dispersed molten film, and then the roll main body portion is thermally packaged into the roll substrate. Outside.

Patent Document 3 describes a method for producing a conductive roller for improving corrosion resistance by spraying a mixed powder containing a WC-Ni cermet and a remaining amount of a Ni-based self-fluxing alloy on a surface of a roll made of SS400, followed by remelting. Treatment to form a film layer.

Patent Document 4 describes a method of manufacturing a conductive roller. A self-fluxing alloy spray layer containing WC cermet was formed on the surface of the SS400 roll, and a WC cermet layer was formed thereon.

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. Hei 1-194860

Patent Document 2: Japanese Patent Laid-Open No. Hei 5-295592

Patent Document 3: Japanese Patent Laid-Open Publication No. 2002-88461

Patent Document 4: Japanese Patent Laid-Open No. 2006-183107

In Patent Document 1, in the plating solution of a strong acid having a pH of less than 1, the plating solution is wetted from the surface of the film by continuous use, so that the adhesion between the roll base material and the spray film is lowered, and the film is self-supporting from the surface of the base material. The problem of flaking. In fact, in Patent Document 1, it is not implemented in an environment as harsh as pH 1 is not required, and the implementation conditions only show a current density range of 5 to 20 A/dm ² , and the operation time is also relatively high. It is as short as 1000 hours, so it is not carried out for a long period of time such as one-month continuous operation. Further, since the film is thermally melted after the spraying, there is also a problem that the manufacturing cost is increased.

In Patent Document 2, in the plating solution of a strong acid having a pH of less than 1, the plating solution is wetted from the surface of the film by continuous use, so that the adhesion between the roll base material and the spray film is lowered, and the film is self-supporting. The problem of surface peeling. Further, since the edge of the roller is corroded by the plating solution, there is a problem that the yield of the product is lowered due to the chipping. Further, it is necessary to re-melt the roll after the spraying, and there is also a problem that the time and cost for regenerating the roll including the hot-sleeve insertion become large.

In Patent Document 3, in the plating solution of a strong acid having a pH of less than 1, the plating solution is wetted from the surface of the film by continuous use, so that the adhesion between the roll base material and the spray film is lowered, and the film is self-supporting. The problem of surface peeling. Further, it is necessary to re-melt the roll after the spraying, and there is also a problem that the time and cost for the roll regeneration become large. Further, when the film is to be applied to the stainless steel roll, the grain boundary is cracked by the heating of the stainless steel due to the remelting treatment, and the roll is broken. Therefore, it is only necessary to use carbon steel having low corrosion resistance, and there is also a problem that the acid-corroded carbon steel fragments reduce the yield of the product.

In Patent Document 4, in the plating solution of a strong acid having a pH of less than 1, the plating solution is wetted from the surface of the film by continuous use, so that the adhesion between the roll base material and the spray film is lowered, and the film is self-supporting. The problem of surface peeling. In fact, in the test for acid corrosion by immersion in the plating solution in Patent Document 4, pH = 3.0, and the test under an environment where the pH is less than 1 is not performed. Further, it is necessary to re-melt the roll after the spraying, and there is also a problem that the time and cost for the roll regeneration become large. Further, when the film is to be applied to the stainless steel roll, the remelting treatment causes cracks in the grain boundary due to the heating of the stainless steel, so that the roll is broken. Therefore, it is necessary to use carbon steel with low corrosion resistance, and there is also a problem that the acid-corroded carbon steel fragments reduce the yield of the product.

As described above, the conventional conductive roller is basically characterized in that carbon steel is used as a roll material, and a coating layer of a NiCr-based alloy is formed on the surface of the roll for the purpose of preventing the reaction between the carbon steel and the plating solution. Further, the coating layer is characterized in that it contains a carbide (or cermet) mainly composed of WC for the purpose of preventing abrasion due to friction with the steel sheet. As a result, in the acid plating bath of pH ≧1, the reaction or abrasion can be greatly reduced, and the life of the roll can be ensured and the defective rate can be lowered.

However, in such a conventional conductive roller, in the strong acid plating bath having a pH of <1, the amount of acid corrosion of the carbon steel itself is greatly increased, and in addition, the corrosion resistance of the coating layer containing the carbide itself is insufficient. Therefore, there is a problem that the cost of manufacturing the roller is large but the effect obtained is small. That is, in the roll using the conventional technique and the surface treatment technique thereof, it is difficult to have both high abrasion resistance and high corrosion resistance to a strong acid having a pH of less than 1.

Further, it has been found that the conventional film obtained by adhering the molten film to the carbon steel roll base material is damaged by acid corrosion due to the molten film and the base material, and thus the chips are scattered into the plated product to cause a recess and pressure. Defective products such as marks cause a decrease in product yield. Further, it is known that in a general electroplating tin process, there is a phenomenon in which tin ions in the plating solution change to metal tin and electrodeposition occurs on the surface of the roll. Further, the electrodeposited metallic tin also causes defects such as indentation, and this tendency becomes apparent when the above-mentioned conventional roller is used.

Accordingly, the present invention has been made in view of the above problems, and an object thereof is to provide a cermet powder which can produce a cermet film which has both high abrasion resistance and high corrosion resistance to a strong acid having a pH of less than 1. Further, an object of the present invention is to provide a protective film covering member, a plating bath roll, and a method for producing the same, which have high abrasion resistance and high corrosion resistance to a strong acid having a pH of less than 1.

The gist of the present invention for solving the above problems is as follows.

(1) A cermet powder comprising: 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 containing 8 mass% or more Chromium as a carbide or gold in the above matrix metal Genus or alloying element.

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

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

The cermet powder according to any one of the above (1), wherein the molybdenum carbide particles have a particle size ranging from 0.1 to 6 μm.

(5) A protective film covering member comprising a stainless steel base material and a cermet film formed on the stainless steel base material, wherein the cermet film-based tungsten carbide particles and molybdenum carbide particles are dispersed in a Ni-containing film 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 contains 8% by mass or more of chromium. As a carbide or a metal or alloying element in the above matrix.

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

(7) The protective film coating member according to the above (5) or (6), wherein, in the cermet film, the tungsten carbide particles have a particle size ranging from 0.1 to 6 μm.

(8) The protective film coating member according to any one of the above (5), wherein, in the cermet film, the molybdenum carbide particles have a particle size ranging from 0.1 to 6 μm.

The protective film covering member according to any one of the above aspects, wherein the cermet film has a surface roughness Ra of 0.5 to 10 μm.

(10) A method for producing a protective film covering member, comprising the step of spraying the cermet powder according to any one of the above (1) to (4) on a stainless steel substrate.

(11) The method for producing a protective film covering member according to the above (10), wherein the spraying is a high velocity oxygen fuel (HVOF) spraying.

(12) A protective coating film according to any one of the above (5) to (9).

(13) A roll for a plating bath, wherein the roll shaft portion and the roll main body portion each include stainless steel, and the roll main body portion only includes the protective film covering member according to any one of the above (5) to (9).

(14) A method of producing a roll in a plating bath, characterized in that the cermet powder according to any one of the above (1) to (4) is only melted on a roll portion and the roll body portion includes a roll of stainless steel A cermet film is formed on the roller body portion of the member.

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

According to the cermet powder of the present invention, a cermet film having both high abrasion resistance and high corrosion resistance to a strong acid having a pH of less than 1 can be produced. Further, the protective film covering member of the present invention and the roll in the plating bath can have both high abrasion resistance and high corrosion resistance to a strong acid having a pH of less than 1.

100‧‧‧Protective coatings

10‧‧‧Substrate (stainless steel)

200‧‧‧electroplating bath

20‧‧‧Metal ceramic film

22‧‧‧Material

24‧‧‧Carbide particles (WC particles, Mo ₂ C particles, arbitrary Cr ₃ C ₂ particles)

300‧‧‧Electroplating bath

30‧‧‧ Roller shaft

32‧‧‧ Roller body

34‧‧‧Metal ceramic film (spray film)

Figure 1 is a schematic cross-sectional view of a protective film covering member 100 according to an embodiment of the present invention. Surface map.

Fig. 2(A) is a schematic cross-sectional view showing a conventional roll 200 in an electroplating bath, and Fig. 2(B) is a schematic cross-sectional view showing a roll 300 in an electroplating bath according to an embodiment of the present invention.

(cermet powder)

The cermet powder according to the embodiment of the present invention is characterized in that it contains 40% by mass or more of tungsten carbide particles, 10 to 40% by mass of molybdenum carbide particles, and Ni or a Ni alloy as a matrix metal, and further contains 8 mass% or more. The chromium is used as a carbide or a metal or alloying element contained in the above-mentioned matrix metal. According to the cermet powder, a cermet film having high abrasion resistance and high corrosion resistance to a strong acid having a pH of less than 1 can be produced. Hereinafter, each element of the cermet powder of the present invention will be described.

The tungsten carbide particles exert a high abrasion resistance and a relatively high corrosion resistance to the cermet film. Examples of the tungsten carbide particles include WC particles. The content of the tungsten carbide particles must be 40% by mass or more. The reason for this is that the abrasion resistance of the cermet film cannot be sufficiently obtained in the case of less than 40% by mass. Further, the content of the tungsten carbide particles is preferably 70% by mass or less. The reason for this is that when it exceeds 70% by mass, the cermet film cannot obtain a high corrosion resistance to a strong acid having a pH of less than 1 because the content of other components becomes small. From the viewpoint of surely 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.

The molybdenum carbide particles exhibit a function of not only imparting high wear resistance to the cermet film but also imparting high corrosion resistance to a strong acid having a pH of less than 1. Examples of the molybdenum carbide particles include Mo ₂ C particles. The content of the molybdenum carbide particles must be 10 to 40% by mass. The reason for this is that, in the case of less than 10% by mass, the cermet film cannot obtain high corrosion resistance to a strong acid having a pH of less than 1, and in the case of more than 40% by mass, other components, particularly carbonization, have to be made. The content of the tungsten particles is small, and the wear resistance of the cermet film cannot be sufficiently obtained. The particle size range of the molybdenum carbide particles is preferably in the range of 0.1 to 6 μm from the viewpoint of surely obtaining the effects of the present invention.

The cermet powder of the present invention contains Ni or a Ni alloy as a matrix metal. Examples of the Ni alloy include a NiCr-based alloy containing Ni as a main component, a NiCrMo-based alloy, and a NiCoCrAlY-based alloy. Ni, which is a matrix metal, exerts an effect of imparting high corrosion resistance to a strong acid having a pH of less than 1 to the cermet film. From this point of view, the Ni content in the cermet powder is preferably 5% by mass or more. Further, the Ni content in the cermet powder is preferably 20% by mass or less in relation to the preferable content of the other components.

The cermet powder of the present invention contains 8% by mass or more of chromium as a carbide or a metal or alloying element contained in the above-mentioned matrix metal. This chromium exerts an effect of imparting high corrosion resistance to a strong acid having a pH of less than 1 to the cermet film. From this viewpoint, the content must be 8% by mass or more. The chromium content in the cermet powder is preferably 20% by mass or less in relation to the preferable content of the other components. Further, in the case where the cermet powder of the present invention contains chromium carbide particles (Cr ₃ C ₂ particles), the particle size range is preferably in the range of 0.1 to 6 μm from the viewpoint of obtaining the effect of the present invention.

The cermet powder of the present invention preferably contains the above components and unavoidable impurities.

In the cermet powder of the present invention, the molybdenum content is preferably chromium from the viewpoint of imparting high corrosion resistance to a strong acid having a pH of less than 1 to the cermet film. Above the content.

The method for producing the cermet powder of the present invention is not particularly limited, and it can be produced by a known method such as a melt pulverization method, a sintering pulverization method, or a granulation sintering method, or any method.

(Protective film covering member, method for producing the same, and electroplating bath roll and method for producing the same)

Referring to Fig. 1, a protective film covering member 100 according to an embodiment of the present invention has 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 using the cermet powder of the present invention as a molten material and spraying it on the substrate 10. As a result, the cermet film 20 is in a state in which the tungsten carbide particles and the molybdenum carbide particles are contained, and the carbide particles 24 optionally containing chromium carbide are dispersed in the matrix 22 containing Ni or a Ni alloy. The content and the particle size range of the tungsten carbide particles in the cermet film 20, the content of the molybdenum carbide particles and the particle size range, the Ni content, the chromium content, and the particle size range of the carb carbide particles are the same as those described for the cermet powder. Further, the plate bath in the embodiment of the present invention includes the above-described protective film covering member 100. The protective film covering member of the present invention and the roller in the plating bath can have both high abrasion resistance and high corrosion resistance to a strong acid having a pH of less than 1.

In the present embodiment, referring to Fig. 2(B), it is particularly preferable that the cermet powder of the present invention is only fused to the roller body portion 32 in which the roller shaft portion 30 and the roller body portion 32 each include a stainless steel roller member. A cermet film 34 is formed thereon to produce a roll 300 in the plating bath.

The protective film covering member of the present invention, the method for producing the same, the roll in the plating bath, and the method for producing the same are completed based on the findings of the inventors and the like as described below. By.

As described above, in the strong acid plating bath having a pH of <1 such as a methanesulfonic acid solution, the life of the conventional roll or the yield of the product is largely lowered. In order to clarify this phenomenon, research measures have been focused on the electrochemical reaction generated by the rolls in the plating solution. First, it is considered that the conductive roller in the plating bath is subjected to a substitution reaction including the following two main reactions different from the usual corrosion reaction: Fe (or Ni in the coating layer, etc.) is a corrosion reaction in which ions become ions in the surface and are dissolved in the solution ( Anode reaction); on the other hand, the Sn ion in the solution undergoes an electrodeposition reaction (cathode reaction). For the reaction, for example, when the roll component is Fe and the plating component is Sn, it can be expressed as follows.

Cathodic reaction: Sn ²⁺ +2e ^- →Sn (1)

Anode reaction: Fe→Fe ²⁺ +2e ^- (2)

The reaction of the above formulas (1) and (2) is an electrochemical 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. In the surface of the conductive roller in such an electrochemical reaction environment, a portion where the potential is locally increased (anode) is subjected to a dissolution reaction, and a portion where the potential is locally lowered (cathode) is subjected to an electrodeposition reaction.

Regarding the portion where the reaction occurs, when the corrosion potential is relatively high when the roller is immersed in the solution, it can be uniformly distributed as a microscopic observation, and the corrosion is uniformly performed over the entire surface. As a result, the surface morphology is obtained. The initial good state can be maintained. However, in the case where the plating solution is a strong acid having a pH of <1 or the current density of the plating is set too high, a portion where a cathodic reaction or an anodic reaction occurs is fixed to a local portion and reacted. In such a case, the surface morphology greatly changes as described below, and the plated product may be damaged.

First, the analysis of the plating components such as Sn caused by the cathodic reaction Out, there is a tendency to concentrate on the part where the precipitation occurs first and grow in the form of metal. Further, after the grown metal deposit grows to a certain size, it falls off due to a load such as friction with the steel sheet, and the portion where the cathode reaction is concentrated is transferred to another place. By repeating such a reaction, precipitation of a plated metal such as Sn is unevenly performed on the surface, and fragments of the plated metal which are detached at the same time may damage the surface of the steel sheet as a product.

Further, when the anodic reaction is fixed at a specific portion and concentrated, the specific element (Fe or the like in the roll) constituting the portion is selectively dissolved at the grain boundary or the like, and as a result, one of the surface of the roll or a part of the cover layer may become Debris and fall off. The debris from the surface may damage the surface of the steel sheet as a product.

That is, with respect to the above-described conventional type of roller, in the case of a strong acid plating bath having a pH of <1 or when the current density is too high, the corrosion potential is relatively lowered, and the microscopic uniformity of the distribution of the anode and the cathode is destroyed. Adhesion, shedding, or partial breakage of the surface of the roll becomes conspicuous by being fixed locally, and as a result, product yield may be lowered.

Therefore, in the case of a strong acid plating bath having a pH of <1 or when the current density is set to be high in order to increase the line speed, in order to ensure the life of the roll and maintain a high product yield, it is necessary to focus not only on the reaction. Also, it is necessary to find a material which can prevent the phenomenon that the cathode reaction or the anode reaction is fixed to a localized and concentrated reaction as described above. On the other hand, if such a material is present, the local corrosion as described above can be prevented, and the life of the roll and the yield of the product can be ensured.

Therefore, the static immersion test of the roll raw material was carried out in a tin plating solution of methanesulfonic acid having a pH of <1, and the time change of the corrosion potential was measured, and the degree of the substitution reaction was evaluated. As a result, when carbon steel was used as the roll material, the amount of reaction was extremely high, and metal Sn was precipitated on all parts of the surface, and the precipitated metal Sn was repeatedly grown and dropped. In comparison with this, stainless steel such as SUS316L is used as the roll material. In the case of the material, the amount of the reaction was greatly lowered, and a thin reaction layer was formed on the surface, but the precipitation of the apparent metal Sn could not be confirmed. Further, the reaction layer on the surface can be easily removed by washing with water and chemical cleaning, and precipitation of the metal Sn cannot be confirmed on the surface which has been removed. Further, when the corrosion potential at the point of 20 days after the immersion was compared, it was found that the stainless steel had a higher potential than the carbon steel by 0.1 V or more and maintained a high potential.

Judging from these results, even in a strong acid solution having a pH of <1, if the corrosion potential is higher than that of carbon steel by about 0.1 V, the reaction amount is small, and the anode and the cathode of the surface are less likely to be immobilized. However, since the hardness of stainless steel is at most about HV200, there is a low abrasion resistance to friction with the steel sheet. Therefore, further research was conducted on materials for protecting the coating layer of stainless steel. As a material for protecting stainless steel, it must be high in hardness, excellent in abrasion resistance, and exhibits good corrosion resistance in a strong acid plating bath. It is understood that the carbide cermet is expected to be such a material, but if it is described in Patent Documents 1 to 4, good characteristics cannot be obtained. However, it has been judged that these carbide cermets have the possibility of improving the electrochemical characteristics in the strong acid plating bath by adjusting the composition, and efforts have been made.

In other words, a sample made of stainless steel as a base material and coated with more than 10 kinds of molten carbide cermet powders including a commercially available product by a HVOF spray method is prepared, and a strong acid having a pH of <1.0 is used. Impregnation experiment of plating solution. As a result, it was found that the Ni or NiCr-based alloy is excellent for the cermet matrix, and good corrosion resistance can be obtained in the case where the carbide contains Mo carbide instead of the WC particles alone. Therefore, as a result of further research, it has been found that in order to obtain high corrosion resistance in a strong acid solution, it is preferable to contain an alloying element containing 8% by mass or more of Cr as a carbide or a matrix, and the content of Mo contained as a carbide is higher. It is desirable to be at least equal to or higher than the content of Cr. Further, it has been found that Mo _{2C is} preferably Mo ₂ C, and even if the content of Mo contained in the cermet is more than the content of Cr, the corrosion resistance is not impaired, but conversely, compared with the content of Cr When the content is less than half, it is difficult to obtain the desired corrosion resistance.

That is, as a carbide cermet film for protecting a stainless steel from a strong acid solution having a pH of <1 without being affected by the above-mentioned displacement reaction and ensuring sufficient wear resistance to sliding with a steel sheet, it is preferable The tungsten carbide particles and the molybdenum carbide particles are dispersed in a matrix containing Ni or a Ni alloy. In the cermet film, the content of the tungsten carbide particles is 40% by mass or more, and the content of the molybdenum carbide particles is 10%. 40% by mass, and further contains 8% by mass or more of chromium as a metal or alloying element in a carbide or a matrix. As a matrix containing Ni as a main component, good results were obtained in a NiCr-based alloy, a NiCrMo-based alloy, and a NiCoCrAlY-based alloy.

A result of a constant current anode-cathode polarization dissolution test of a test piece obtained by forming a protective film by forming a protective film on a stainless steel by HVOF sputtering on a stainless steel, and forming a reaction layer less Compared with stainless steel, the surface morphology is better. Further, as a result of measurement of the corrosion potential, a potential of about 0.1 V higher than that of the stainless steel was obtained. The above results show that the uniformity of the distribution of the anode and the cathode formed on the surface of the carbide cermet film formed by the HVOF spray is achieved at a finer level than that of the stainless steel, and it is understood that there is almost no steel sheet. The reaction product is damaged. It has been found that a protective film having excellent abrasion resistance and exhibiting good corrosion resistance even in a strong acid plating bath can be formed.

Here, it has been confirmed that the method of the wear resistance and the corrosion resistance which are mutually trade-off relations is important to adjust the particle size of the tungsten carbide particles and the molybdenum carbide particles which are the main components of the cermet. That is, it can be seen that if the carbide as a main component of the cermet is made When the particle size is less than 0.1 μm, the abrasion resistance is remarkably lowered, and when the particle size is 6 μm or more, the microscopic uniformity of the distribution of the anode and the cathode in the solution tends to be insufficiently maintained. When it is confirmed that the particle size of the tungsten carbide particles and the molybdenum carbide particles is in the range of 0.1 to 6 μm, both wear resistance and corrosion resistance can be obtained.

It is known that as a method of forming a protective film, a high-speed flame spraying method such as HVOF or high-speed air fuel (HVAF) is preferable. For example, if the cermet film obtained by a high-speed flame spraying method such as HVOF or HVAF is compared with a cermet film obtained by plasma spraying or other spraying method, the porosity thereof is greatly different. With respect to the film obtained by a spraying method other than a high-speed flame such as HVOF or HVAF, the solution penetrates into the inside of the film and the like, and it is difficult to maintain a good surface state. Further, when the obtained film is heat-treated at a high temperature in order to lower the porosity, the carbide is decarburized to form a lower carbide or form a reaction phase with the matrix component, and the wear resistance and corrosion resistance are remarkably lowered. . This tendency is also confirmed in the film formed by the overlay welding or coating method. That is, as a method of forming the carbide cermet film, a high-speed flame spraying method such as HVOF or HVAF is preferable.

When the surface roughness Ra of the protective film formed by the high-speed flame spraying method such as HVOF or HVAF exceeds 10 μm, the probability of damage to the steel sheet due to the protrusion of the carbide becomes high, and When the thickness is less than 0.5 μm, the frictional force cannot be sufficiently obtained, and the roller is idling on the steel sheet, and as a result, the surface state of the steel sheet is impaired. Therefore, the surface roughness Ra of the carbide cermet film is preferably 0.5 to 10 μm.

[Examples] <Example 1>

A sample of a conventional roller size and a roller specification of the present invention was prepared and subjected to a 20-day immersion test in a strong acid plating solution (methanesulfonic acid 50 g/L, tin ion concentration 25 g/L) adjusted to pH <1. . Five kinds of samples shown in Table 1 were produced. That is, the No. 1 type substrate is a conventional carbon steel, and the protective film is also a conventional type of sample. On the other hand, in the samples Nos. 2 to 5, the base material was made of stainless steel. Regarding the protective film, No. 2 is a conventional film of the same type as No. 1, and No. 3 to No. 5 is a HVOF film of various carbide cermets using Ni or a Ni-based alloy as a substrate, wherein No. 5 corresponds to the cermet specification of the example of the present invention. In the film of No. 5, the Mo content is 9.4% by mass, the Cr content is 8.7% by mass, the particle size of the WC particles is at least 0.1 μm, and the maximum is 6 μm, and the particle size of the Mo ₂ C particles is at least 0.1 μm and the maximum is 6 μm, and the surface is rough. The degree Ra was 3.0 μm. Each of the samples was prepared such that the exposed portion of the substrate and the portion of the protective film had substantially the same surface area, and the characteristics of the joint portion between the film and the substrate were evaluated.

In order to evaluate the corrosion resistance of the protective film, the mass change (corrosion reduction) of the sample before and after the immersion was measured, and the results are shown in Table 1. In addition to the change in mass, the results of the state of the surface of the protective film after immersion for 20 days and the measured value of the corrosion potential are also shown in Table 1. Further, the results of the Suga abrasion test (#120-SiC paper, load 3.25 kgf, reciprocating 400 times) of the protective film separately provided were shown. Furthermore, the film observation results were evaluated by the following criteria.

◎: almost no change

○: A little change

△: There is a change

×: There is a big change

[Table 1]

According to the results shown in Table 1, it was found that in the plating solution having a pH of 1, the mass was changed in the sample No. 1 to 4 of the conventional specification, particularly in the sample No. 1 in which carbon steel was used as the substrate. It becomes larger and the surface morphology is also worse. Further, in a sample of a conventional specification using carbon steel as a substrate, the boundary between the film and the substrate was largely damaged by corrosion. In contrast, in the sample in which the stainless steel was protected by the cermet film, not only the mass change was small but also the surface morphology was not easily deteriorated. In particular, in the sample No. 5 which is an example of the present invention, the surface morphology was extremely excellent as compared with the others. This case also corresponds to the measurement result of the corrosion potential (the highest in the measurement sample), and it was confirmed that the uniformity of the distribution of the anode and the cathode on the surface of the film was excellent. Further, it is understood that the examples of the present invention are also excellent in terms of abrasion resistance.

<Example 2>

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

According to the results shown in Table 2, in order to improve the corrosion resistance of the plating solution, it is effective to prepare a large amount of Mo ₂ C particles, and in order to improve the wear resistance, it is effective to prepare a large amount of WC particles. Further, it can be seen that in Nos. 4 to 11 which are examples of the present invention, it is possible to have both high abrasion resistance and high corrosion resistance to a strong acid having a pH of less than 1.

Further, in the sample in which the cermet powder described in the present embodiment is made into a protective film by the atmospheric plasma spraying method, the porosity is high and the influence of carbide deterioration or the like is strong, and the corrosion resistance and the resistance are resistant. Abrasiveness does not provide as good a property as a film produced by HVOF spraying.

<Example 3>

An example in which a conventional product and a product of the present invention are applied to a conductive roller of an electroplating production line will be described. 2(A) and 2(B) show the structure of a conventional roller in comparison with the structure of the roller of the present invention. In the conventional roller shown in FIG. 2(A), a carbon steel pipe is thermally sheathed on a copper core to form a shaft portion, and on the other hand, a protective skin is formed by spraying. The carbon steel sleeve of the film is heat-sealed on the roller main body portion formed of a carbon steel pipe to constitute a main body portion, and these are combined as a roller main body. On the other hand, in the present invention shown in Fig. 2(B), it is understood that the molten film is formed on the roll body made of stainless steel, and the roll body can be easily produced. The specification of the film of the present invention is No. 6 of Example 2.

Further, the heat generated by the energization of each of the rolls was measured by a thermal observer, and as a result, it was confirmed that the temperature was 0.14 to 0.16 ° C / min, and there was no problem in the operability. The composition of the plating bath was the same as in Example 1. The pressure of the roll against the steel sheet was 0.2 MPa, and it was carried out at a plate speed of 150 to 490 m/min. The number of days used is 230 days. After the end of use, each roll was pulled from the bath, and the surface roughness and the Sn adhesion amount of the through-plate part were investigated. The results are shown in Table 3.

According to the results shown in Table 3, the surface roughness of the through-plate portion of the conventional roller was reduced from Ra 3.0 μm before use to Ra 0.81 μm, which was reduced to nearly 1/4, whereas the roller of the present invention was used. After that, Ra was maintained at 1.0 μm or more, and it was confirmed that the life of the film was increased by 30% or more compared with the conventional roller. Further, it is understood that the Sn adhesion amount of the roller of the present invention is reduced by about 10% as compared with the conventional roller. These results are all shown to improve the corrosion resistance of the plating solution and the wear resistance of the steel sheet under the specifications of the present invention. Regarding the defect occurrence rate of the product obtained by actually using each roller, the conventional roller was 2.37% higher, whereas the roller of the present invention was 0.43%, and was successfully reduced to 1/5 or less. It is considered that the reason is that the corrosion resistance is increased, and the film is damaged or coarsened due to the cause of the indentation. The rate of generation of fragments of deposited Sn is greatly reduced.

Further, it can be seen from the results of the same actual operation that the surface roughness of the roll is at least Ra of about 0.5 μm, and if the initial surface roughness exceeds Ra by 10 μm, the frequency of damage to the product is increased. Therefore, the surface roughness of the cermet film of the present invention is preferably set to Ra 0.5 to 10 μm.

(industrial availability)

The cermet powder of the present invention can be preferably used as a material for a protective film (cermet film) in a protective film covering member such as a roll in an electroplating bath. The roll in the plating bath of the present invention can be preferably used as, for example, a conductive roll or the like even in an electroplating bath of a strong acid having a pH of less than 1.

10‧‧‧Substrate (stainless steel)

20‧‧‧Metal ceramic film

22‧‧‧Material

24‧‧‧Carbide particles (WC particles, Mo ₂ C particles, arbitrary Cr ₃ C ₂ particles)

100‧‧‧Protective coatings

Claims (15)

A cermet powder comprising: 40% by mass or more of tungsten carbide particles, 10 to 40% by mass of molybdenum carbide particles, and Ni or a Ni alloy as a matrix metal, and further containing 8% by mass or more of chromium As a carbide or a metal or alloying element contained in the above matrix metal. The cermet powder of claim 1, wherein the content of the tungsten carbide particles is 70% by mass or less. The cermet powder according to claim 1 or 2, wherein the tungsten carbide particles have a particle size ranging from 0.1 to 6 μm. The cermet powder according to any one of claims 1 to 3, wherein the molybdenum carbide particles have a particle size ranging from 0.1 to 6 μm. A protective film covering member comprising a stainless steel substrate and a cermet film formed on the stainless steel substrate; wherein the cermet film is composed of tungsten carbide particles and molybdenum carbide particles dispersed in a 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, 8% by mass or more of chromium is contained as a carbide. Or a metal or alloying element in the above matrix. The protective film-coated member according to claim 5, wherein the content of the tungsten carbide particles is 70% by mass or less. The protective film covering member according to claim 5 or 6, wherein in the cermet film, the tungsten carbide particles have a particle size ranging from 0.1 to 6 μm. The protective film-coated member according to any one of claims 5 to 7, wherein in the cermet film, the molybdenum carbide particles have a particle size ranging from 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. A method of producing a protective film covering member comprising the step of spraying the cermet powder of any one of claims 1 to 4 onto a stainless steel substrate. The method of producing a protective film covering member according to claim 10, wherein the spraying is a high velocity oxygen fuel (HVOF) spraying. An electroplating bath roll characterized by comprising the protective film covering member according to any one of claims 5 to 9. An electroplating bath roll characterized in that the roll shaft portion and the roll main body portion each include stainless steel, and only the roll main body portion includes the protective film covering member according to any one of claims 5 to 9. A method for producing a roll in an electroplating bath, characterized in that the cermet powder according to any one of claims 1 to 4 is only melted on the roll main body portion of the roll member and the roll main body portion including the stainless steel roll member A cermet film is formed. A method of producing a roll in an electroplating bath according to claim 14, wherein the above-described spray is HVOF spray.