TWI623624B - Metal-ceramic powder, protective coating member and its manufacturing method, and roller in electroplating bath and its manufacturing method - Google Patents

Abstract

The invention provides a cermet powder capable of producing a cermet film with high wear resistance and high corrosion resistance to strong acids with a pH less than 1. The cermet powder of the present invention is characterized by containing 40% by mass or more of tungsten carbide particles, 10-40% by mass of molybdenum carbide particles, and Ni or Ni alloy as a matrix metal, and further containing 8% by mass or more of chromium as carbonization Metal or alloy elements contained in the metal or the above matrix metal.

Description

Metal-ceramic powder, protective coating member and its manufacturing method, and roller in electroplating bath and its manufacturing method

The invention relates to a cermet powder, a protective film-covered member and a method for manufacturing the same, a roller in an electroplating bath, and a method for manufacturing the same.

Conventionally, as a method of manufacturing a conductive roller used in an electroplating bath, the following are proposed. Patent Document 1 describes a method for manufacturing a conductive roller, which is on the surface of a carbon steel roller and uses Co or Ni as a main component and an alloy added with Cr, C, Fe, Mo, etc. as a spray material, After plasma arc spraying is carried out under a low-pressure oxygen-free environment, the thermal melting treatment of the film heated by the plasma arc is performed again in the same environment to form a non-porous spray film.

Patent Document 2 describes a method for manufacturing a conductive roller for electroplating, which is characterized by being formed by spraying a mixed powder containing carbide cermet powder and C-containing nickel-chromium alloy powder on the surface of a carbon steel roll body The spray coating layer, after which, the spray coating layer is heated to re-precipitate the carbide to form a re-precipitated carbide dispersion spray coating film, and thereafter, the roller body is thermally fitted onto the roller base material Outside.

Patent Document 3 describes a method for manufacturing a conductive roller with improved corrosion resistance. The surface of the SS400 roller is sprayed with a mixed powder containing WC-Ni cermet and the remaining amount of Ni-based self-fluxing alloy, and then re-melted Process to form a film layer.

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

[Prior Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. 1-198460

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

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

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

In Patent Document 1, under a strong acid plating solution with a pH of less than 1, the plating solution is infiltrated from the surface of the coating film due to continuous use, so there is a decrease in the adhesion between the roller base material and the spray coating film, and the coating film is from the surface of the base material The problem of exfoliation. In fact, in Patent Document 1, it is not implemented in a harsh environment like pH less than 1, and the implementation conditions also only show a lower current density range of 5~20A/dm ² and the operating time is also lower. As short as 1000 hours, it is not a long-term implementation such as continuous operation for 1 month. Furthermore, the film is thermally melted after spraying, so there is also a problem of increased manufacturing costs.

In Patent Document 2, also under a strong acid plating solution with a pH of less than 1, the plating solution infiltrates from the surface of the coating film due to continuous use, so there is a decrease in the adhesion between the roller base material and the spray coating film, and the coating film is from the base material The problem of surface peeling. In addition, since the edge of the roller is corroded by the plating solution, there is a problem that the yield of the product is reduced due to the fragments. In addition, the roller must be re-melted after melt-spraying, and there is also a problem that the time and cost for the regeneration of the roller including the insertion of the hot sleeve increases.

In Patent Document 3, under a strong acid plating solution with a pH of less than 1, the plating solution is infiltrated from the surface of the coating film due to continuous use, so there is a decrease in the adhesion between the roller base material and the spray coating film, and the coating film is from the base material The problem of surface peeling. In addition, the rollers must be remelted after melt-spraying, and there is also a problem that the time and cost of roller regeneration increases. In addition, if this coating is to be applied to a stainless steel roller, the grain boundary is cracked due to the heating of the stainless steel due to the remelting treatment, so the roller may be damaged. Therefore, the carbon steel with low corrosion resistance has to be used, and there is also a problem that the fragments of the carbon steel corroded by the acid reduce the yield of the product.

In Patent Document 4, under a strong acid plating solution with a pH of less than 1, the plating solution is infiltrated from the surface of the coating film due to continuous use, so there is a decrease in the adhesion between the roller base material and the spray coating film, and the coating film is from the base material The problem of surface peeling. In fact, in the acid corrosion test performed by immersion in a plating solution in Patent Document 4, pH=3.0, and no test under a severe environment such as a pH less than 1 was performed. In addition, the rollers must be remelted after melt-spraying, and there is also a problem that the time and cost of roller regeneration increases. In addition, if this coating is to be applied to a stainless steel roller, the remelting treatment causes cracks in the grain boundary due to the heating of the stainless steel, so the roller may be damaged. Therefore, carbon steel with lower corrosion resistance must be used, and there is also a problem that acid-corroded carbon steel fragments reduce the yield of products.

As described above, the characteristics of the conventional conductive roller are basically that carbon steel is used as the raw material of the roller, and a coating layer of NiCr-based alloy is formed on the roller surface for the purpose of preventing the reaction between the carbon steel and the plating solution. In addition, the coating layer is characterized by containing carbide (or cermet) mainly composed of WC for the purpose of preventing wear due to friction with the steel plate. As a result, in an acidic plating bath with pH≧1, the reaction or abrasion can be greatly reduced, and the life of the roller can be ensured and the defect rate can be reduced.

However, regarding such a conventional conductive roller, if it is in a strong acid plating bath with a pH<1, the acid corrosion amount of the carbon steel itself greatly increases, and besides, the corrosion resistance of the coating layer containing carbide itself is also insufficient. Therefore, there is a problem that the cost of roll manufacturing is relatively large but the effect obtained is relatively small. That is, it is difficult to have both high abrasion resistance and high corrosion resistance to strong acids with a pH of less than 1 in the roller using conventional technology and its surface treatment technology.

Furthermore, it can be seen that the conventional spray-coated film is attached to the carbon steel roll base material because the spray-coated film and base material are damaged due to acid corrosion, so the chips fly into the plated product to cause depressions and pressure. Defective products such as marks cause a decrease in product yield. In addition, it is known that in the general tin plating process, there is a phenomenon that tin ions in the plating solution change to metallic tin, and electrodeposition occurs on the roller surface. In addition, the electrodeposited metal tin also causes defective products such as indentation, and there is also a problem that this tendency becomes obvious when the above-mentioned conventional roller is used.

Therefore, in view of the above problems, the present invention aims to provide a cermet powder capable of producing a cermet film having both high abrasion resistance and high corrosion resistance to strong acids with a pH of less than 1. In addition, an object of the present invention is to provide a protective film-coated member having a high wear resistance and a high corrosion resistance to a strong acid having a pH of less than 1, a roll in an electroplating bath, and a method for manufacturing the same.

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

(1) A cermet powder characterized by 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% by mass or more Chromium as carbide or gold in the above matrix metal Is an alloy element.

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

(3) The cermet powder as described in (1) or (2) above, wherein the particle size range of the tungsten carbide particles is in the range of 0.1 to 6 μm.

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

(5) A protective coating member comprising a stainless steel substrate and a cermet coating formed on the stainless steel substrate, wherein the cermet coating is composed of tungsten carbide particles and molybdenum carbide particles dispersed in Ni Or Ni alloy matrix, and 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 carbide or metal or alloy element in the above matrix.

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

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

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

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

(10) A method for manufacturing a protective coating member, comprising the step of melt-spraying the cermet powder described in any one of (1) to (4) above on a stainless steel substrate.

(11) The method for manufacturing a protective film-coated member as described in (10) above, wherein the melt spraying is a high velocity oxygen fuel (HVOF) spray.

(12) A roll in an electroplating bath, characterized by comprising the protective film coating member described in any one of (5) to (9) above.

(13) A roller in an electroplating bath, characterized in that both the roller shaft portion and the roller body portion include stainless steel, and only the roller body portion includes the protective film-covering member described in any one of (5) to (9) above.

(14) A method for manufacturing a roll in an electroplating bath, characterized in that the cermet powder described in any one of (1) to (4) above is melt-sprayed only on a roll in which the roller shaft portion and the roller body portion include stainless steel A cermet coating is formed on the roller body portion of the member.

(15) The method for manufacturing a roll in an electroplating bath as described in (14) above, wherein the spraying is HVOF spraying.

According to the cermet powder of the present invention, a cermet film having both high wear resistance and high corrosion resistance to strong acids with a pH less than 1 can be produced. In addition, the protective film-coated member of the present invention and the roller in the electroplating bath can have both high wear resistance and high corrosion resistance to strong acids with a pH of less than 1.

100‧‧‧Protection coating member

10‧‧‧ Base material (stainless steel)

200‧‧‧plating bath roller

20‧‧‧Ceramic film

22‧‧‧Matrix

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

300‧‧‧plating bath middle roller

30‧‧‧Roller shaft

32‧‧‧Roll main body

34‧‧‧Ceramic film (melt-sprayed film)

FIG. 1 is a schematic cross section of a protective coating member 100 according to an embodiment of the present invention Face map.

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

(Metal ceramic powder)

A cermet powder according to an embodiment of the present invention is characterized by containing 40% by mass or more of tungsten carbide particles, 10-40% by mass of molybdenum carbide particles, and Ni or Ni alloy as a matrix metal, and further containing 8% by mass or more Chromium is used as carbide or metal or alloy element contained in the above matrix metal. According to the cermet powder, a cermet film having both high wear resistance and high corrosion resistance to strong acids with a pH below 1 can be produced. Hereinafter, each element of the cermet powder of the present invention will be described.

Tungsten carbide particles play a role in imparting higher wear resistance and relatively higher corrosion resistance to the cermet coating. Examples of tungsten carbide particles include WC particles. The content of tungsten carbide particles must be 40% by mass or more. The reason for this is that the wear resistance of the cermet coating cannot be sufficiently obtained when it is less than 40% by mass. In addition, the content of tungsten carbide particles is preferably 70% by mass or less. The reason for this is that when the content exceeds 70% by mass, the content of other components becomes small, so that the cermet film cannot obtain high corrosion resistance to strong acids with a pH of less than 1. From the viewpoint of surely obtaining the effect 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 are a more important component in the present invention that exerts the effect of not only imparting higher wear resistance to the cermet coating, but also imparting higher corrosion resistance to strong acids with a pH of less than 1. Examples of molybdenum carbide particles include Mo ₂ C particles. The content of molybdenum carbide particles must be 10 to 40% by mass. The reason is that when less than 10% by mass, the cermet film cannot obtain high corrosion resistance to strong acids with a pH less than 1, and when it exceeds 40% by mass, other components, especially carbonization, have to be carbonized The content of tungsten particles becomes smaller, and the wear resistance of the cermet coating cannot be fully obtained. From the viewpoint of surely 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 invention contains Ni or Ni alloy as a matrix metal. Examples of Ni alloys include NiCr-based alloys, NiCrMo-based alloys, and NiCoCrAlY-based alloys having Ni as a main component. Ni, which is a matrix metal, exerts a function of imparting a high corrosion resistance to a strong acid with 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. In addition, in terms of the relationship with the preferable content of other components, the Ni content in the cermet powder is preferably 20% by mass or less.

The cermet powder of the present invention contains 8% by mass or more of chromium as a carbide or a metal or alloy element contained in the above matrix metal. This chromium functions to impart a high corrosion resistance to a strong acid with a pH of less than 1 to the cermet film. From this viewpoint, the content must be 8% by mass or more. In terms of the relationship with the preferable content of other components, the chromium content in the cermet powder is preferably 20% by mass or less. In addition, when 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 surely 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, from the viewpoint of imparting higher corrosion resistance to a strong acid with a pH of less than 1 to the cermet film, the molybdenum content is preferably chromium Above the content.

The production method of 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 sinter pulverization method, a granulation sintering method, or any method.

(Protection film-coated member and its manufacturing method, and plating bath roller and its manufacturing method)

Referring to FIG. 1, a protective coating member 100 according to an embodiment of the present invention has a stainless steel substrate 10 and a cermet coating 20 formed on the stainless steel substrate. The cermet film 20 is formed by spraying the cermet powder of the present invention on the base material 10 as a spray material. As a result, the cermet film 20 is in a state where carbide particles 24 containing tungsten carbide particles and molybdenum carbide particles, and optionally chromium carbide, are dispersed in the matrix 22 containing Ni or Ni alloy. The content and particle size range of tungsten carbide particles in the cermet film 20, 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 are the same as those described above for the cermet powder. In addition, the roll in the electroplating bath according to one embodiment of the present invention includes the protective film coating member 100 described above. The protective film-coated member of the present invention and the roller in the electroplating bath can have both higher wear resistance and higher corrosion resistance to strong acids with 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 be sprayed only on the roller body portion 32 and the roller body portion 32 including the roller body portion 32 of the stainless steel roller member. The cermet film 34 is formed thereon, and the in-bath roll 300 is manufactured.

The protective film-coated member of the present invention and its manufacturing method, and the roller in the electroplating bath and its manufacturing method are completed based on the insights of the present inventors as described below By.

As described above, in a strong acid plating bath such as methanesulfonic acid solution having a pH of less than 1, the life of conventional rollers or product yields are greatly reduced. In order to clarify this phenomenon, the countermeasures are studied, focusing on the electrochemical reaction generated by the roller in the plating solution. First of all, it is considered that the conductive roller in the plating bath undergoes a substitution reaction including the following two main reactions different from the ordinary corrosion reaction: Fe (or Ni in the coating layer) becomes ions on the surface and dissolves in the solution in the corrosion reaction ( Anode reaction); on the other hand, Sn ions in the solution undergo electrodeposition reaction (cathode reaction). Regarding these reactions, for example, when the roller component is Fe and the plating component is Sn, it can be expressed as follows.

Cathode ^{reaction: Sn 2+ + 2e - → Sn} (1)

Anode ^{reaction: Fe → Fe 2+ + 2e -} (2)

The reactions of the above formulas (1) and (2) are electrochemical equivalents, 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 conductive roller under such an electrochemical reaction environment, a dissolution reaction occurs at a portion where the potential locally becomes higher (anode), and an electrodeposition reaction occurs at a portion where the potential locally becomes lower (cathode).

With regard to the sites where these reactions occur, when the corrosion potential when the roller is immersed in the solution is relatively high, it can be regarded as uniformly distributed on the microscopic observation, and the corrosion is performed uniformly over the entire surface. As a result, the surface morphology Can maintain the initial good condition. However, under conditions where the plating solution is a strong acid with a pH <1, or the current density of the plating is set too high, the site where the cathodic reaction or the anodic reaction occurs may be fixed locally to carry out the reaction. In this case, the surface morphology changes greatly as described below, which may damage the plated product.

First, the analysis of Sn and other plating components caused by the cathode reaction Out, there is a tendency for the reaction to concentrate on the site where the precipitation first occurs and grow in the form of metal. Moreover, after the grown metal deposits grow to a certain size, they fall off due to friction such as friction with the steel plate, and the part where the cathode reaction is concentrated is transferred to other places. By repeating this reaction, the plating metal such as Sn is unevenly deposited on the surface, and the fragments of the plated metal falling off may damage the surface of the steel plate as a product.

In addition, if the anode reaction is fixed at a specific site to concentrate the reaction, the specific elements (Fe in the roll, etc.) constituting the site will selectively dissolve at the grain boundary, etc. As a result, a part of the roll surface or a part of the coating layer may become Fall off. The debris falling off the surface may damage the surface of the steel plate used as the product.

That is, regarding the roller of the above-mentioned conventional type, in a strong acid plating bath with a pH<1 or when the current density is too high, the corrosion potential is relatively reduced, and the microscopic uniformity of the distribution of the anode and the cathode is destroyed. The attachment, peeling or partial damage of the roller surface becomes obvious because it is fixed locally, and as a result, the product yield may be reduced.

Therefore, in a strong acid plating bath with a pH<1, or if the current density is set to be high in order to increase the line speed, in order to ensure the life of the roller and maintain a high product yield, it is necessary to focus not only on the reaction It is also necessary to find a material that can prevent the phenomenon where the cathode reaction or anode reaction is fixed as a partial and concentrated reaction as described above. Conversely, if such a material is present, the local corrosion as described above can be prevented, and the life of the roller and product yield can be ensured.

Therefore, a static immersion test of the roller raw material was carried out in a tin plating solution using methanesulfonic acid with pH<1, the time change of the corrosion potential was measured, and the degree of displacement reaction was evaluated. As a result, it can be seen that when carbon steel is used as the roll material, the reaction amount is extremely high, and metal Sn is precipitated at all parts of the surface, and the precipitated metal Sn blocks repeatedly grow and fall off. In contrast, stainless steel such as SUS316L is used as the roll material In the case of the material, the reaction amount is greatly reduced, and a thin reaction layer is formed on the surface, but no obvious precipitation of metal Sn can be confirmed. In addition, the reaction layer on the surface can be easily removed by water washing and chemical cleaning, and the precipitation of metal Sn cannot be confirmed on the removed surface. In addition, the corrosion potential at the time point after 20 days after immersion was compared. As a result, it was found that the potential of stainless steel was higher than that of carbon steel by 0.1 V or more, and the state of high potential was maintained.

Judging from these results, even in a strong acid solution with a pH <1, if it is stainless steel with a corrosion potential higher than about 0.1 V compared to carbon steel, the reaction amount is small, and it is not easy to fix the anode and cathode on the surface. However, since the hardness of stainless steel is at most about HV200, there is a possibility that the wear resistance to friction with the steel plate is low. Therefore, the materials used to protect the coating of stainless steel are further studied. As a material for protecting stainless steel, it must be of high hardness, excellent wear resistance, and exhibit good corrosion resistance in a strong acid plating bath. It is known that carbide cermets are promising as such materials, but those described in Patent Documents 1 to 4 cannot obtain good characteristics. However, it is judged that these carbide cermets have the possibility to improve the electrochemical characteristics in the strong acid plating bath by adjusting the composition, and diligent research is conducted.

That is, a sample made of stainless steel as a base material and coated with more than 10 kinds of carbide cermet powders for spraying by the HVOF spraying method on the surface, including a commercially available sample, is prepared, and a strong acid with a pH <1.0 Dipping experiment of plating solution. As a result, it has been found that Ni or NiCr-based alloys are superior to the cermet matrix, and good corrosion resistance can be obtained when the carbide contains Mo carbide instead of WC particles alone. Therefore, further research was conducted, and as a result, it was found that in order to obtain higher corrosion resistance in a strong acid solution, it is more desirable to contain 8% by mass or more of Cr as an alloy element of carbide or matrix, and the content of Mo contained as carbide is Ideally, it should be at least equal to or higher than the Cr content. Furthermore, it was found that Mo ₂ C is preferably Mo ₂ C. Even if the content of Mo contained in the cermet is greater than the content of Cr, the corrosion resistance will not be impaired, but on the contrary, compared with the content of Cr, Mo When the content is less than half, it is difficult to obtain the required corrosion resistance.

That is, as a carbide cermet film used to protect stainless steel from the substitution reaction as described above in a strong acid solution with a pH<1, and to ensure sufficient wear resistance against sliding action with the steel plate, it is more desirable The following: it is made of tungsten carbide particles and molybdenum carbide particles dispersed in a matrix containing Ni or Ni alloy. In the cermet coating, the content of tungsten carbide particles is 40% by mass or more, and the content of molybdenum carbide particles is 10~ 40% by mass, further containing 8% by mass or more of chromium as a metal or alloy element in the carbide or matrix. As a matrix containing Ni as a main component, good results are obtained in NiCr-based alloys, NiCrMo-based alloys, and NiCoCrAlY-based alloys.

The results of the constant current anode-cathode polarization dissolution test of the test piece obtained by forming a protective cladding film by HVOF spraying on stainless steel and forming a carbide cermet film satisfying the conditions shown above also rarely form a reaction layer Compared with stainless steel, the surface shape is better. In addition, regarding the measurement result of the corrosion potential, a potential higher than that of stainless steel by about 0.1 V was obtained. The above results show that the uniformity of the distribution of the anode and cathode formed on the surface of the carbide cermet film formed by HVOF spraying is achieved at a finer level than stainless steel, and it can be seen that there is almost no steel plate due to The product may be damaged due to the reaction product. It was found that in this way, a protective film having excellent wear resistance and exhibiting good corrosion resistance even in a strong acid plating bath can be formed.

Here, it was confirmed that it is important to adjust the particle size of the tungsten carbide particles and molybdenum carbide particles as the main components of the cermet as a method of abrasion resistance and corrosion resistance having a trade-off relationship. That is, it can be seen that if the carbide as the main component of the cermet makes If the particle size is less than 0.1 μm, the wear resistance is significantly reduced, and if the particle size is 6 μm or more, the microscopic uniformity of the distribution of the anode and cathode in the solution cannot be sufficiently maintained. It was confirmed that when the particle size of the tungsten carbide particles and the molybdenum carbide particles is in the range of 0.1 to 6 μm, both abrasion resistance and corrosion resistance can be achieved.

It is known as a method of forming a protective film, and a high-speed flame spraying method such as HVOF and high velocity air fuel (HVAF) is preferred. For example, if the cermet film obtained by high-speed flame spraying methods such as HVOF and HVAF is compared with the cermet film obtained by plasma spraying or other spraying methods, the porosity is very different. Regarding the coating film obtained by the spraying method other than high-speed flame such as HVOF and HVAF, the solution penetrates into the interior of the coating film, etc., and it is difficult to maintain a good surface state. In addition, if the obtained film is heat-treated at a high temperature in order to reduce the porosity, the carbide will decarburize to form lower-grade carbide, or form a reaction phase with the matrix component, and the wear resistance and corrosion resistance will be significantly reduced. . This tendency is also confirmed in the coating formed by the overlay welding or coating method. That is, as a method of forming a carbide cermet film, a high-speed flame spraying method such as HVOF and HVAF is preferable.

It can be seen that the protective film formed by high-speed flame spraying methods such as HVOF, HVAF, etc., when the surface roughness Ra exceeds 10 μm, the probability of damage to the steel plate due to the protrusion of carbide becomes higher. In the case of less than 0.5 μm, the friction force cannot be obtained sufficiently, and the roller is idling on the steel plate, as a result of which the surface state of the steel plate is damaged. Therefore, the surface roughness Ra of the carbide cermet coating is preferably 0.5 to 10 μm.

[Example] <Example 1>

Prepare samples of conventional roller specifications and roller specifications of the present invention, and perform a 20-day immersion test in a strong acid plating solution (methanesulfonic acid 50g/L, tin ion concentration 25g/L) adjusted to pH<1. . Five kinds of samples shown in Table 1 were prepared. That is, the No. 1 series base material is a conventional type carbon steel, and the protective film is also a conventional type sample. In contrast, in the samples No. 2 to 5, the base material was stainless steel. Regarding the protective film, No. 2 uses the same conventional type film as No. 1, and No. 3 to No. 5 use HVOF films of various carbide cermets with Ni or Ni-based alloys as the matrix. Among them, No. 5 corresponds to the cermet specification of the example of the present invention. In the coating of No. 5, the Mo content is 9.4% by mass, the Cr content is 8.7% by mass, the particle size of WC particles is minimum 0.1 μm and maximum 6 μm, the particle size of Mo ₂ C particles is minimum 0.1 μm and maximum 6 μm, and the surface is rough The degree Ra is 3.0 μm. Each sample was made in such a way that the exposed substrate and the protective film had approximately equal surface areas, and the characteristics of the joint between the film and the substrate were also 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 Table 1, in addition to the quality change, the results of observing the state of the surface of the protective film after immersion for 20 days by an electron microscope and the measured values of the corrosion potential are also shown. In addition, the results of the Suga abrasion test (#120-SiC paper, load 3.25 kgf, 400 reciprocating times) of the protective film additionally implemented are also shown. In addition, the film observation results were evaluated by the following criteria.

◎: Almost no change

○: There is a slight change

△: There is a change

×: Significant changes

[Table 1]

According to the results shown in Table 1, in the plating solution with pH<1, the mass changes in sample Nos. 1 to 4 of the conventional specifications, especially sample No. 1 using carbon steel as the base material It becomes larger and the surface morphology becomes worse. Furthermore, in samples of conventional specifications using carbon steel as the base material, the boundary between the film and the base material is greatly damaged due to corrosion. Compared with this, it can be seen that in the sample protected by stainless steel with a cermet coating, not only the quality change is small, but also the surface morphology is not likely to deteriorate. Especially in Sample No. 5 which is an example of the present invention, the surface morphology is extremely good compared to other samples. This situation also corresponds to the measurement result of the corrosion potential (the highest among the test samples), confirming that the uniformity of the distribution of the anode and cathode on the surface of the film is excellent. In addition, it can be seen that the present invention example is also excellent in terms of wear resistance.

<Example 2>

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

According to the results shown in Table 2, it is effective to prepare a large amount of Mo ₂ C particles to improve the corrosion resistance to the plating solution. To improve the wear resistance, it is effective to prepare a large amount of WC particles. Furthermore, it is understood that Nos. 4 to 11 as examples of the present invention can have both high wear resistance and high corrosion resistance to strong acids with a pH of less than 1.

In addition, in the sample in which the cermet powder described in this example was made into a protective film by the atmospheric plasma spray method, the porosity became higher and the effects of carbide deterioration were stronger, and the corrosion resistance and resistance None of the abrasion properties can achieve the characteristics as good as those produced by HVOF spraying.

<Example 3>

An example in which conventional products and products of the present invention are applied to conductive rollers of an electroplating production line and compared will be described. 2(A) and (B) show the structure of the conventional roller and the structure of the roller of the present invention. In the conventional roller shown in FIG. 2(A), a carbon steel tube is thermally sheathed on a copper shaft 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 thermally sheathed on the roller body formed of the carbon steel pipe to form the body, and these combinations are used as the roller body. On the other hand, in the present invention shown in FIG. 2(B), it can be seen that it is sufficient to form a spray coating on the roller body made of stainless steel, and it is extremely easy to produce the roller body. The specification of the film of the present invention adopts No. 6 of Example 2.

In addition, the heat generated by the energization of each roller was measured by a heat observer, and it was confirmed that they were all 0.14 to 0.16°C/min, which was a level where there was no problem with operability. The composition of the plating bath is the same as in Example 1. The pressure of pressing the roller against the steel plate is 0.2MPa, and it is carried out within the range of 150~490m/min. The number of days of use is 230 days. After use, each roller was pulled from the bath, and the surface roughness of the through-plate portion and the amount of Sn adhesion 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 is reduced from Ra 3.0 μm before use to Ra 0.81 μm, and reduced to nearly 1/4. On the contrary, the roller of the present invention is used in use After maintaining Ra 1.0 μm or more, it can be confirmed that the life of the film is improved by more than 30% compared with the conventional roller. In addition, it can be seen that the amount of Sn adhered to the roller of the present invention is reduced by about 10% compared to the conventional roller. These results show that under the specifications of the present invention, the corrosion resistance to the plating solution and the wear resistance to the steel plate can be improved. Regarding the defective rate of products obtained by actually using each roller, the conventional roller has a relatively high rate of 2.37%. In contrast, the roller of the present invention has a rate of 0.43%, which has been successfully reduced to less than 1/5. It is believed that the reason is that due to the improvement of corrosion resistance, the film that is the cause of the indentation is damaged or thickened. The generation rate of Sn-deposited fragments is greatly reduced.

Furthermore, according to the results of the same actual machine operation, the use limit of the roller is that the surface roughness is at least Ra 0.5 μm. If the initial surface roughness exceeds Ra 10 μm, the frequency of product damage will increase. Therefore, the surface roughness of the cermet coating of the present invention is preferably Ra 0.5 to 10 μm.

(Industry availability)

The cermet powder of the present invention can be preferably used as a material for a protective coating (metal-ceramic coating) in a protective coating member such as a roller in an electroplating bath. The roll in the electroplating bath of the present invention can be preferably used as, for example, a conductive roll even in a plating bath with a strong acid having a pH of less than 1.

Claims (13)

A cermet powder, characterized by comprising: 40 to 70% by mass 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% by mass or more Chromium is a metal or alloy element contained in carbide or the above-mentioned matrix metal. The cermet powder according to claim 1, wherein the particle size range of the tungsten carbide particles is in the range of 0.1 to 6 μm. The cermet powder according to claim 1 or 2, wherein the particle size range of the molybdenum carbide particles is in the range of 0.1 to 6 μm. A protective coating member comprising a stainless steel substrate and a cermet coating formed on the stainless steel substrate; characterized in that the cermet coating is composed of tungsten carbide particles and molybdenum carbide particles dispersed in Ni or Ni alloy Formed in the matrix, and in the cermet film, the content of the tungsten carbide particles is 40 to 70% by mass, the content of the molybdenum carbide particles is 10 to 40% by mass, and further contains 8% by mass or more of chromium as carbonization Metal or alloy elements in the above-mentioned substance or the above matrix. The protective film-coated member according to claim 4, wherein in the cermet film, the particle size range of the tungsten carbide particles is in the range of 0.1 to 6 μm. The protective film-coated member according to claim 4 or 5, wherein in the cermet film, the particle size of the molybdenum carbide particles ranges from 0.1 to 6 μm. The protective film-coated member according to claim 4 or 5, wherein the surface roughness Ra of the cermet film is 0.5 to 10 μm. A method for manufacturing a protective film-coated member, comprising the step of melt-spraying the cermet powder of any one of claims 1 to 3 on a stainless steel substrate. The method for manufacturing a protective film-coated member according to claim 8, wherein the above-mentioned melt injection is high speed oxygen fuel (HVOF, high velocity oxygen fuel) melt injection. A roll in an electroplating bath, characterized by comprising the protective coating member of any one of claims 4 to 7. A roll in an electroplating bath, characterized in that both the roll shaft portion and the roll body portion include stainless steel, and only the roll body portion includes the protective film covering member of any one of claims 4 to 7. A method for manufacturing a roll in an electroplating bath, characterized in that the cermet powder according to any one of claims 1 to 3 is melted and sprayed only on the roll body part of the roll member in which the roll shaft part and the roll body part both include stainless steel Instead, a cermet coating is formed. The method for manufacturing a roll in an electroplating bath according to claim 12, wherein the above-mentioned spraying is HVOF spraying.