TW202003921A - Method for manufacturing sliding parts capable of securely and quickly obtaining a sliding part having an improved adhesion resistance and smoothness - Google Patents

Abstract

The present invention provides a method for manufacturing sliding parts, which is capable of securely and quickly obtaining a sliding part having an improved adhesion resistance and smoothness. A method for manufacturing sliding parts, which is a method for manufacturing sliding parts including cemented carbide or cermet sliding parts. The method for manufacturing sliding parts is characterized by including: a surface modification step of subjecting the surface of a sliding part to wet-etching by using a solution to remove the metal phase near the surface, wherein the solution contains nitric acid with a concentration of more than 10% by mass and less than 55%, and the dissolution rate of the metal phase contained in the sliding part is 0.5 mg/min or more. The temperature of the solution during the wet etching is preferably adjusted to 20 DEG C to 90 DEG C.

Description

Manufacturing method of sliding parts

The invention relates to a manufacturing method of sliding parts.

Composite alloys including hard phases represented by ceramics and metal phases represented by Ni, Co, Fe, etc. are excellent in impact resistance at room temperature and high temperature, so they are used in various applications such as molds or cutting tools Sliding parts. In order to improve the wear resistance of the sliding parts made of the composite alloy, various studies have been conducted previously. For example, in Patent Document 1, in order to improve the wear resistance or hardness of a cemented carbide, a cemented carbide has been disclosed, which is mainly composed of tungsten carbide (WC), which is characterized by , The surface layer is substantially only exposed with WC particles, or only components other than iron group metals and WC particles are exposed, and the average particle size of the WC particles in the surface layer is larger than the average particle size of the internal WC particles, and/or the surface hardness Greater than internal hardness. According to Patent Document 1, the cemented carbide can be applied to cutting tools or wear-resistant sliding tools, and it also describes that by exposing the surface of the WC-based cemented carbide to excited plasma, only WC particles are exposed Of cemented carbide.

In Patent Document 2, a method for manufacturing a wear-resistant metal body has been disclosed. In order to obtain a wear-resistant metal body with excellent wear resistance, the surface of the cemented carbide is etched with an acid to make the vaporized copper The hard alloy surface is liquefied to impregnate copper into the grain boundaries of tungsten particles. The super hard alloy is formed by bonding tungsten carbide particles by a bonding phase. In addition, Patent Document 2 also describes the following manufacturing method, which can be applied not only to a mold but also to a cemented carbide in various fields where wear is a problem. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 07-11375 [Patent Document 2] Japanese Patent Laid-Open No. 2010-24519

[Problems to be solved by the invention]

In the sliding parts as described above, on the one hand, along with the requirements of further refinement or use in a more severe environment, the smoothness of the working surface of the sliding parts is maintained, so that the materials to be processed are attacked without abrasion Powder, on the one hand, also pays attention to the improvement of productivity, safety or cost reduction. On the other hand, as described in the patent literature, there are few examples of the etching of cemented carbide, and depending on the combination of the material and the solution, the progress of the etching may be slow. In addition, when a mixed acid solution such as aqua regia with strong oxidizing power is selected, although the etching ability itself is not a problem, the reaction proceeds continuously, and gas is easily generated during use. Therefore, there is a risk of adverse effects on the human body and the container may break during storage, and care must be taken during operation, and there may be cases where management costs or disposal costs increase. Regarding the solution of the above-mentioned problem, it is not described in Patent Literature 1 or Patent Literature 2, and there is room for further investigation. Therefore, an object of the present invention is to provide a method for manufacturing a sliding part, which can safely and quickly obtain a sliding part having both good adhesion resistance and smoothness. [Means to solve the problem]

The present invention has been completed in view of the above-mentioned problems. That is, the present invention is a method for manufacturing a sliding part, which is a method for manufacturing a sliding part including cemented carbide or cermet. The method for manufacturing a sliding part is characterized by including: In the surface modification step, the surface of the sliding part is wet-etched with a solution to remove the metal phase near the surface. The solution contains nitric acid with a mass percentage concentration greater than 10% and less than 55%. The dissolution rate of the contained metal phase is above 0.5 mg/min.

Preferably, the temperature of the solution during the wet etching is 20°C to 90°C. [Effect of invention] According to the present invention, it is possible to safely and quickly obtain a sliding part having both good adhesion resistance and smoothness.

The present invention will be described in detail below. However, the present invention is not limited to the embodiments listed here, and can be appropriately combined or improved without departing from the technical idea of the invention. The sliding component of this embodiment includes cemented carbide or cermet, and therefore has the characteristics of having both excellent strength, high ductility, and toughness. Here, the so-called superhard alloy of the present embodiment means a composite alloy including a hard phase and a metal phase, the hard phase including carbide of W, the metal phase is selected from Fe, Ni, Co, Cr and has Phase. In addition, the cermet refers to a composite alloy including a hard phase and a metal phase selected from at least one of Group IV transition metals, Group V transition metals, Group VI transition metals other than W, Al, and Si Carbides, nitrides, oxides, carbonitrides, the metal phase is selected from Fe, Ni, Co, Cr and has a role as a bonding phase. The preferred cermet composition is at least one selected from Group 4 transition metals, Group 5 transition metals, and Group 6 transition metals other than W. In addition, the so-called sliding parts in this embodiment refer to parts that are in contact with the target material and only one of the members slides or slides against each other. As an example of the sliding part, a mold may be mentioned.

In this embodiment, before the surface modification step described later, the following shape processing step may also be performed: the surface of the prepared raw material for sliding parts is prepared by grinding, grinding, cutting, and electrical discharge machining Adjust to surface roughness (Ra)≦0.1 μm. By using the shape processing step to smooth the surface of the raw material for sliding parts, especially the surface that becomes the working surface, the surface of the sliding parts formed by the subsequent surface modification step can be adjusted to be smooth and formed in an appropriate manner Face of the recess. The upper limit of Ra of the surface of the raw material for sliding parts after a preferable shape processing step is 0.05 μm, and the upper limit of Ra is more preferably 0.02 μm. The lower limit of Ra is not particularly limited, but it can be set to 0.001 μm in consideration of mass productivity, for example. Here, the shape processing step may combine a plurality of steps, and may also be adjusted to Ra≦0.1 μm by finishing processing by grinding after rough processing by grinding processing, for example. In the polishing at this time, an existing polishing method can be used, but in order to surely obtain a desired surface roughness, polishing using a diamond paste may also be performed.

In the manufacturing method of the present embodiment, the main feature is the following surface modification step: etching the surface of the prepared raw material for cemented carbide or cermet sliding parts to remove the metal phase near the surface. By applying the manufacturing method of this embodiment, it is possible to form a structure in which the metal phase which is soft and easily adheres to the material to be processed does not substantially exist on the working surface of the sliding part (the surface in contact with the material to be processed), Therefore, it can be expected to significantly improve the adhesion resistance and greatly increase the life of the mold. In this embodiment, wet etching is applied in the surface modification step. As an etching method, there is also dry etching using discharge plasma, but dry etching using plasma has longer processing steps than wet etching, and is in a region where it is difficult to substantially include only the hard phase (hereinafter, also referred to as The strengthening layer) tends to be thick, so it is not good. By applying wet etching, the region where substantially no metal phase exists and only the hard phase is formed can be formed thick. In addition, when removing the metal phase, there may be a portion that is not completely removed, so in this embodiment, it is assumed that "there is substantially no metal phase." If the amount of the metal phase of the reinforced layer is significantly different from that of the non-reinforced layer, that is, the main part of the sliding part including the hard phase and the metal phase (parts other than the surface), it is easy to determine that it is not substantially There is a strengthening layer of the metal phase layer. In addition, the reinforcement layer is preferably a layer containing materials other than the hard phase and the void, or the hard phase and the metal phase filling the void. The void may be formed by removing the metal phase, or it may still be a void, or the void may be filled with materials other than the metal phase. Of course, some voids may remain.

In the surface layer modification step of this embodiment, the etching solution is a solution containing nitric acid (mass% concentration) of 55% or less (hereinafter, also referred to as nitric acid solution). By using a nitric acid solution adjusted to the above concentration, the metal phase on the surface of the cemented carbide or cermet can be quickly dissolved, and the strengthening layer required for the sliding part of the present invention can be quickly formed. When using aqua regia or a nitric acid solution with a concentration greater than 55%, the metal phase is passivated due to excessive oxidizing power, and the etching rate tends to decrease. In addition, aqua regia is a mixed acid, so its safety is not good, and it is difficult to store it. Therefore, the necessary amount is generated every time, so there is a tendency that the management cost and the like increase. The upper limit of the preferred nitric acid concentration is 50%, more preferably 45%, even more preferably 40%, still more preferably 35%. In addition, if the concentration is too low, the dissolving power of the metal phase decreases, so the lower limit of the nitric acid concentration is set to more than 10%. Furthermore, the lower limit is preferably 15%, more preferably 20%, and still more preferably 25%. In this embodiment, by using the nitric acid solution, the dissolution rate of the metal phase contained in the sliding part can be adjusted to 0.5 mg/min or more (preferably 0.7 mg/min or more, more preferably 0.9 mg/min or more, Furthermore, it is more preferably 1.1 mg/min or more), which tends to form a reinforcement layer on the surface of the sliding part in a shorter time, which is also advantageous in forming the reinforcement layer more uniformly. In addition, the nitric acid solution of this embodiment may add an acidic solution other than water, ethanol, nitric acid, etc. to adjust the concentration in a range that does not reach the above-mentioned dissolution rate. The upper limit of the dissolution rate does not need to be specified. Moreover, for example, 10.0 mg/min, 7.0 mg/min, 5.0 mg/min, 3.0 mg/min, etc. can be set.

In the surface layer modification step by wet etching of this embodiment, the temperature of the nitric acid solution is preferably 20°C to 90°C. By adjusting to the above temperature, the evaporation of the aqueous solution or excessive generation of bubbles can be suppressed, so that the wet etching can be performed more stably. The upper limit of the preferable temperature is 70°C, more preferably 50°C, and still more preferably 40°C. In addition, the etching treatment time can be appropriately adjusted from 0.5 min to 30 min in accordance with the shape or use of the part. The upper limit of the preferred etching treatment time is 15 min, more preferably 10 min, even more preferably 8 min, and particularly preferably 6 min. The lower limit of the preferred etching time is 1 min.

As described above, by performing a surface modification step on a component using cemented carbide or cermet as described above, a reinforced layer containing a hard phase is formed, thereby obtaining a sliding component that has greatly improved abrasion resistance or adhesion resistance . The reinforcing layer is preferably formed until the sliding part is at least 0.2 μm in the depth direction from the surface of the working surface, and the sliding part is produced by the manufacturing method of the present embodiment. Thereby, the sticking resistance can be further improved. The reinforcement layer is more preferably formed to a range of at least 0.5 μm in the depth direction from the surface of the working surface, and still more preferably formed to a range of 1 μm.

In addition, in this embodiment, in order to further improve the abrasion resistance or the adhesion resistance, the sliding parts after the surface layer modification step may be coated with a hard film. As the type of the hard film, for example, a hard film or a diamond-like carbon film may be coated. The hard film includes a transition metal selected from Group IV, a Group V transition metal, a Group VI transition metal, Si and One or more of Al carbide, nitride, carbonitride, oxide, and boride. The film can be adjusted to a desired thickness within a range that does not damage the surface shape obtained in the surface modification step. The thickness of the preferable film is 2 μm or less, and the thickness of the more preferable film is 1 μm or less. [Example]

Prepare eight sliding parts made of cemented carbide (12.7 mm×12.7 mm×4.8 mm). The sliding parts made of cemented carbide choose WC as the hard phase and Co as the metal phase. Co’s relative to WC and Co’s The total content is 11 wt%. At this time, the surface of the sliding part has been adjusted to Ra≦0.1 μm by polishing. Separately, 50 ml of solutions under the conditions shown in Table 1 were prepared. Nitric acid 1.38 (made by Kanto Chemical Co., Ltd., special grade, purity 60% to 61%) is used in nitric acid with a concentration of 60 wt%. Nitric acid at a concentration of 10 wt% and 30 wt% is produced by mixing nitric acid 1.38 in pure water. Aqua regia is produced by using hydrochloric acid (made by Kanto Chemical Co., Ltd., special grade, 35% to 37% purity) and nitric acid 1.38, with a mixing ratio of three parts hydrochloric acid and one part nitric acid. The prepared sliding parts are immersed in the treatment tank containing the solution for two or five minutes to perform surface modification treatment. The temperature of the solution at this time is 20°C to 25°C in both the inventive example and the comparative example. Then, the data of two minutes of dipping time and five minutes of data were connected by a straight line, and the dissolution rate of Co was evaluated based on the inclination of the straight line. The amount of Co dissolution was evaluated by spraying a diluted test solution in the plasma, determining the type of the contained component based on the wavelength of the emitted light beam emitted from the excited atoms and ions, and obtaining it based on its intensity Content, the plasma is generated by applying high frequency to Ar gas using an inductively coupled plasma (Inductively Coupled Plasma, ICP) emission spectrometer (SII Nano Technology Co., Ltd., SPS3100H). The analysis results are shown in Figure 1.

[Table 1]

According to FIG. 1, each dissolution rate is 1.3 mg/min in Example 1 of the present invention, 0.3 mg/min in Comparative Example 1, 0.6 mg/min in Comparative Example 2, and 0.2 mg/min in Comparative Example 3. It was confirmed that the sample of Example 1 of the present invention using nitric acid at a concentration of 30 wt% in the etching solution dissolved a large amount of Co in a shorter time than the comparative example. In particular, when compared with Comparative Example 3, which is an example using aqua regia, it can be confirmed that Co dissolves at a rate of about four times or more. From this, it can be confirmed that the example of the present invention can modify the surface layer of the sliding component at a low cost and in a short time. In the sample of Example 1 of the present invention, a strengthening layer containing a hard phase was formed to a depth of 0.2 μm or more on the surface after the etching. In addition, various hard coatings may be coated on the surface after the etching, for example, within a thickness range of 2 μm or less.

no

FIG. 1 is a graph showing the amount of Co eluted in the examples of the present invention and the comparative example.

Claims (2)

A manufacturing method of a sliding part, the sliding part includes a super hard alloy or a cermet, the manufacturing method of the sliding part is characterized by comprising: In the surface modification step, the surface of the sliding part is wet-etched with a solution to remove the metal phase near the surface. The solution contains nitric acid with a mass percentage concentration greater than 10% and less than 55%. The dissolution rate of the metal phase contained is 0.5 mg/min or more. The method for manufacturing a sliding part according to item 1 of the patent application range, wherein the temperature of the solution during the wet etching is 20°C to 90°C.

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