Surface treatment method of member, tool steel with hard film and member

Abstract

To strengthen both of a substrate surface and a hard film, of a member made by forming the hard film when using sintered composite material or alloy tool steel as substrate, and to improve durability and wear resistance, etc.SOLUTION: Fine particle projection treatment is performed by using fine particle media comprising a ductile metal material of Hv500 or less having a hardness lower than a substrate of a member, with respect to such a member as to form a hard film on a surface of the substrate. With respect to such a member as to form a hard film on the surface of the substrate by setting sintered composite material or alloy tool steel as base material, the fine particle projection treatment is performed by using any of tungsten, molybdenum and a metal amterial having a specific gravity of 9 g / cm3 or more, any compound consisting essentially of them and, or fine particle media obtained by mixing at least two of them.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a surface treatment technology by microparticle projection treatment (also referred to as shot material projection treatment, microparticle peening treatment, etc.).

Background Art

[0002] Cemented carbide and the like, which is one of the sintered composite materials obtained by mixing and sintering powders of hard compounds with a metal binder (hereinafter also simply referred to as sintered composite materials), have high hardness second only to diamond and ceramics, and excellent wear resistance can be expected compared to tool steel and the like. Therefore, it is widely used in molds, machine parts, cutting tools, etc.

[0003] However, sintered composite materials obtained by mixing and sintering powders of hard compounds such as cemented carbide and cermet with a metal binder have problems such as being prone to cracking and chipping and having low toughness. Therefore, in reality, it is difficult to apply them to molds and the like that are subject to high loads. On the other hand, an increase in the demand for cemented carbide molds is expected for processing with a large load (for example, press load, etc.) and high-precision products.

[0004] For this reason, the present applicants proposed in Patent Document 2 a technique capable of improving the flexural strength and fracture toughness value by shotting cemented carbide, cermet, etc. with a medium having a lower hardness and a higher specific gravity than these objects to be treated.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, in the cutting edges of tools made of sintered composite materials such as cemented carbide, cermet, and iron-based alloys, a coating (film formation) is applied to the surface of the sintered composite material serving as the base material, thereby imparting functions such as oxidation resistance, lubricity, and mold release properties, with wear resistance being the foremost.

[0007] For this reason, for example, in Patent Document 3, a TiN film (titanium nitride hard film) or a DLC film (diamond-like carbon hard film) is applied to the cutting edge of a cutting tool, and small-diameter projected particles with a hardness of 550 HV or more are projected onto it by shot peening to increase the hardness of these hard films and improve wear resistance. Such a proposal has been made.

[0008] Furthermore, recently, there has been a demand to further increase the hardness of a single layer of the coating layer (hard film) applied to the surface of the sintered composite material, and thus further improve wear resistance and the like.

[0009] That is, when the base material is a sintered composite material and a hard film is formed on its surface, a technology is required that can strengthen both the surface of the base material and the hard thin film to suppress breakage and peeling, and improve durability, wear resistance, and the like.

[0010] Also, for alloy tool steels such as high-speed steel (high-speed tool steel), if there is a technology that can strengthen both the surface of the base material and the hard thin film when a hard film is formed on its surface to suppress breakage and peeling, and improve durability, wear resistance, and the like, it would be beneficial.

[0011] The present invention has been made in view of such circumstances, and aims to provide a surface treatment method for a member that can strengthen both the surface of the base material and the hard film of a member having a sintered composite material (for example, cemented carbide, cermet, etc.) or alloy tool steel as the base material and a hard film formed on its surface, and improve durability, wear resistance, and the like, as well as a tool steel and a member with a hard film whose durability, wear resistance, and the like have been improved by the surface treatment method.

Means for Solving the Problems

[0012] Therefore, the surface treatment method of the member according to the present invention is as follows: For a member having a sintered composite material or alloy tool steel as a base material and a hard film formed on the surface of the base material, a particulate projection treatment is performed using a particulate medium made of a ductile metal material having a hardness of 500 Hv or less, which is lower than that of the base material of the member, or a compound thereof.

[0013] In the present invention, the particulate medium can be characterized in that it is any one of stainless steel, copper, molybdenum disulfide, iron, nickel, chromium, or a compound having any of these as a main component, or a particulate medium in which at least two of these are mixed.

[0014] Also, the surface treatment method of the member according to the present invention is as follows: For a member having a sintered composite material or alloy tool steel as a base material and a hard film formed on the surface of the base material, a particulate projection treatment is performed using a particulate medium made of any one of tungsten, molybdenum, or a metal material having a specific gravity of 9 g / cm 3 or more, or a compound having any of these as a main component, or a particulate medium in which at least two of these are mixed.

[0015] In the present invention, the hard film can be characterized in that it is a hard film based on TiN, a hard film based on CrN, or a hard film in which TiN and CrN are fused.

[0016] In the present invention, the sintered composite material can be characterized in that it is a cemented carbide or cermet.

[0017] In the present invention, the cemented carbide can be characterized in that it is a WC-Co based alloy.

[0018] In the present invention, the alloy tool steel can be characterized in that it is a high speed tool steel.

[0019] In addition, the tool steel with a hard film according to the present invention is characterized by being produced using the surface treatment method of the member according to the present invention described above.

[0020] In addition, the member according to the present invention is a member in which a sintered composite material or alloy tool steel is used as a base material and a hard film is formed on the surface of the base material, and on the surface thereof, particulate projection treatment is performed using particulate media made of a ductile metal material having a hardness of 500 Hv or less, which is lower than that of the base material of the member, or a compound thereof.

[0021] In the member according to the present invention, the particulate media can be characterized in that it is any one of stainless steel, copper, molybdenum disulfide, iron, nickel, chromium, or a compound mainly composed of any of these, or a particulate media in which at least two of these are mixed.

[0022] In addition, the member according to the present invention is a member in which a sintered composite material or alloy tool steel is used as a base material and a hard film is formed on the surface of the base material, and on the surface thereof, particulate projection treatment is performed using particulate media made of any one of tungsten, molybdenum, or a metal material having a specific gravity of 9 g / cm 3 or more, or a compound mainly composed of any of these, or a particulate media in which at least two of these are mixed.

[0023] In the member according to the present invention, the hard film can be characterized in that it is a hard film based on TiN, a hard film based on CrN, or a hard film in which TiN and CrN are fused.

Effects of the Invention

[0024] According to the present invention, both the substrate surface and the hard film of a member having a hard film formed on the surface thereof with a sintered composite material (for example, cemented carbide, cermet, etc.) or alloy tool steel as a substrate are strengthened, and durability, wear resistance, etc. can be improved. There are provided a surface treatment method for a member, a tool steel with a hard film, and a member in which durability, wear resistance, etc. are improved by the surface treatment method.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0026] Hereinafter, an embodiment according to the present invention will be described with reference to the accompanying drawings. Note that the present invention is not limited by the embodiments described below.

[0027] As described above, in the cutting edges of tools based on sintered composite materials obtained by mixing and sintering powders of hard compounds such as cemented carbide and cermet (carbides and nitrides of metals, etc.) with a metal binder, or alloy tool steels such as high-speed steel, a coating (film formation) is applied to the surface of the base material to impart functions such as wear resistance, oxidation resistance, lubricity, and mold release properties.

[0028] In addition, it would be beneficial if the hardness of a single layer of a coating layer (hard film, hard thin film) applied to the surface of an alloy tool steel such as a sintered composite material or high-speed steel could be further increased, and thus the wear resistance and the like could be further improved.

[0029] Here, when the base material is a sintered composite material, if a high-hardness medium is used, there is a risk of reducing the flexural strength and fracture toughness of the base material (see paragraphs

[0030] ~

[0031] , FIGS. 1, 2, etc.).

[0032] Therefore, when the base material is an alloy tool steel such as a sintered composite material or high-speed steel and a hard film (also referred to as a hard thin film) is formed on its surface, a technique is required that can strengthen both the surface of the base material and the hard film to suppress breakage and peeling, and improve durability, wear resistance, etc. Also, for an alloy tool steel such as high-speed steel, if there is a technique that can strengthen both the surface of the base material and the hard thin film when a hard film is formed on its surface to suppress breakage and peeling, and improve durability, wear resistance, etc., it would be beneficial. Thus, the inventors of the present invention have conducted various studies, experiments, etc., and as a result, have obtained a beneficial technique.

[0033] Specifically, the following experiments were conducted. Two types of tool steels were prepared as the base materials of the objects to be processed (workpieces). The first one was a cemented carbide (equivalent to K10: the base material polished to a mirror finish (with a surface roughness of, for example, Ra: 0.01 μm or less, Rz: 0.1 μm or less), for example, with a hardness of about 800 - 1800 Hv, about 92 - 93 HRA), and the second one was a high-speed steel (SKH51: the base material polished to a mirror finish (with a surface roughness of Ra: 0.01 μm or less, Rz: 0.1 μm or less)). After these base materials were completely degreased, 3 μm thick hard thin films of titanium nitride (TiN) and chromium nitride (CrN) were respectively deposited using a hollow cathode discharge type ion plating apparatus. For these test pieces, tungsten media (with an average particle size of about 5 μm and a hardness of about Hv250) were used to perform shots (particle projection treatment) at projection pressures of 0.2 MPa and 0.4 MPa respectively, with the distance between the test piece and the projection nozzle being 150 mm. As a comparison, untreated test pieces without particle projection treatment were also evaluated. The tool steels (cemented carbides and other sintered composite materials or high-speed steels) (test pieces) on which such hard thin films were deposited were the objects to be treated by particle projection treatment. Note that the cemented carbide (equivalent to K10) is an example of a WC-Co based alloy. Also, high-speed steel (SKH51) is also called high-speed tool steel. For example, in terms of composition, it contains carbon C: 0.8 - 0.9%, chromium Cr: 3.8 - 4.5%, tungsten W: 6.0 - 7.0%, molybdenum Mo: 4.8 - 5.8%, vanadium V: 1.8 - 2.3%, and the rest is iron Fe.

[0034] <Change in Compressive Residual Stress due to Particle Projection Treatment of Cemented Carbide> The residual stress of each test piece was measured using an X-ray residual stress measuring device "μ-X360s" manufactured by Pulstec Industrial Co., Ltd. Note that the residual stress measuring instrument manufactured by Pulstec Industrial adopts the "cosα method". This is a method of obtaining stress by utilizing the relationship between the diffraction ring measured by the back reflection method from a single oblique incident X-ray and strain, and it is a method of calculating stress from the slope of the cosα diagram.

[0035] X-rays were irradiated from above the hard film to measure the residual stress of the cemented carbide substrate and high-speed steel. However, due to the influence of the stress of the hard film and the attenuation of the X-ray intensity, it cannot be evaluated as an absolute value. However, as shown in Fig. 1, it was confirmed that, as a tendency, compressive stress remained large as the particulate projection treatment was performed and the projection pressure increased.

[0036] As shown in Fig. 1, the measurement results of the compressive residual stress of the test piece of the cemented carbide substrate show that the untreated hard film (TiN) (without particulate projection treatment) is -70 MPa, while for the test piece of the hard film (TiN) projected with tungsten media at 0.2 MPa, the compressive residual stress increased to -100 MPa. Furthermore, for the test piece of the hard film (TiN) projected with tungsten media at 0.4 MPa, the compressive residual stress increased to -212 MPa.

[0037] Also, while the untreated hard film (CrN) (without particulate projection treatment) is -114 MPa, for the test piece of the hard film (CrN) projected with tungsten media at 0.2 MPa, the compressive residual stress increased to -131 MPa. Furthermore, for the test piece of the hard film (CrN) projected with tungsten media at 0.4 MPa, the compressive residual stress increased to -201 MPa.

[0038] Next, the measurement results of the substrate compressive residual stress of the test piece of the high-speed steel substrate are shown in Fig. 2. As shown in Fig. 2, while the untreated hard film (TiN) (without particulate projection treatment) is -100 MPa, for the test piece of the hard film (TiN) projected with tungsten media at 0.2 MPa, the compressive residual stress increased to -472 MPa. Furthermore, for the test piece of the hard film (TiN) projected with tungsten media at 0.4 MPa, the compressive residual stress increased to -1026 MPa.

[0039] Also, while the untreated (without particle projection treatment) hard film (CrN) has a value of -305 MPa, in the test piece of the hard film (CrN) projected with tungsten media at 0.2 MPa, the compressive residual stress increased to -502 MPa. Furthermore, in the test piece of the hard film (CrN) projected with tungsten media at 0.4 MPa, the compressive residual stress increased to -1123 MPa.

[0040] From these results, it was found that when the base material is a tool steel such as cemented carbide (equivalent to K10) or high-speed steel (SKH51), and a 3-μm thick hard thin film of titanium nitride (TiN) or chromium nitride (CrN) is formed on the surface of these base materials, and particle projection treatment is performed using tungsten media from above the hard thin film, the compressive residual stress near the surface of the base material can be increased. As a result, the occurrence of cracks and the like can be suppressed, and by extension, the fracture toughness and the like can be improved.

[0041] Next, the measurement of the hardness of the hard thin film formed on the surface of the test piece will be described. <Measurement of the hardness of the thin film by microscratch> Using a microscratch-type hardness tester (for example, Bruker Hysitron TI980 Triboindenter), the surface of each test piece was scraped a certain number of times, and the hardness of the exposed surface was measured with a pressing load of 8 mN. Here, the measurement was performed only on the test pieces with a cemented carbide base material.

[0042] As shown in Figure 3, the hardness measurement results of the test pieces with a cemented carbide base material show that while the untreated (without particle projection treatment) hard film (TiN) has a hardness of 17.59 GPa, in the test piece projected with tungsten at 0.2 MPa, the hardness increased to 28.12 GPa. Furthermore, in the test piece projected with tungsten at 0.4 MPa, the hardness increased to 34.12 GPa.

[0043] Also, while the untreated (without particle projection treatment) hardness of the hard film (CrN) is 30.05 GPa, the hardness of the test piece projected with tungsten at 0.2 MPa increased to 32.69 GPa, and further, the hardness of the test piece projected with tungsten at 0.4 MPa increased to 36.00 GPa.

[0044] According to the present embodiment, it has been found that by forming a hard film (TiN) and a hard film (CrN) on the surface of a member having a cemented carbide, which is an example of tool steel, as a base material, and further performing a particle projection treatment with a tungsten medium, the hardness of the hard film can be increased, and thus the wear resistance can be improved.

[0045] Next, a confirmation test of the change in crystallinity of the hard thin film formed on the surface of the test piece will be described. <Confirmation of Crystallinity Change of Thin Film by XRD (X-ray Diffraction)> Using "Ultima IV" manufactured by Rigaku Corporation, X-ray diffraction was performed on the surface of each test piece. <Explanation of X-ray Diffraction> X-ray diffraction is the analysis of the diffraction phenomenon that occurs when X-rays are scattered and interfered by electrons around atoms when the sample is irradiated with X-rays. When X-rays having a wavelength (0.5 Å to 3 Å) comparable to the atomic spacing are incident on a substance in which atoms are regularly arranged, the X-rays are scattered by the electrons present around each atom. The scattered X-rays interfere with each other and intensify in a specific direction. This corresponds to the X-ray diffraction phenomenon. The crystal phase is identified by comparing the measured diffraction pattern with the diffraction pattern of a known substance. Since the shape (spectrum) of the X-ray diffraction pattern depends on the arrangement of atoms and molecules constituting the crystal, the diffraction angle and intensity change if the structure is different. Also, it is presumed that the stress changes due to the change (shift) in the peak position, and the crystal is distorted. As shown in FIG. 4, the peak positions of TiN exist at 36.663°, 42.597°, and 61.814°, and the peak positions of CrN exist at 37.516°, 43.594°, and 63.353°.

[0046] The measurement results of X-ray diffraction in this embodiment are shown in FIG. 5. Regarding the TiN hard film, a peak appears at around 41.5°, which cannot be identified as the peak position of TiN or the peak position of the cemented carbide (WC-Co) of the substrate, in the TiN hard film after film formation (untreated: the particle projection treatment is untreated). Then, it can be seen that when the particle projection treatment is performed on this TiN hard film (untreated), the peak around 41.5° disappears. In the X-ray diffraction measurement result diagram of the crystallinity evaluation of TiN in FIG. 5, TiN_W0.4MPa shows the X-ray diffraction measurement result of the test piece obtained by projecting tungsten media at 0.4 MPa on the TiN hard film, TiN_W0.2MPa shows the X-ray diffraction measurement result of the test piece obtained by projecting tungsten media at 0.2 MPa on the TiN hard film, TiN shows the X-ray diffraction measurement result of the TiN hard film after film formation (untreated: the particle projection treatment is untreated), and WC-Co shows the X-ray diffraction measurement result of the cemented carbide (equivalent to K10) of the substrate.

[0047] Also, in FIG. 5, regarding the CrN hard film, peaks appear at around 35.2° and 41.5°, which cannot be identified as the peak position of CrN or the peak position of the cemented carbide (WC-Co) of the substrate, in the CrN hard film after film formation (untreated: the particle projection treatment is untreated). Then, it can be seen that when the particle projection treatment is performed on this CrN hard film (untreated), the peaks around 35.2° and 41.5° disappear. In the X-ray diffraction measurement result diagram of the crystallinity evaluation of CrN in FIG. 5, CrN_W0.4MPa shows the X-ray diffraction measurement result of the test piece obtained by projecting tungsten media at 0.4 MPa on the CrN hard film, CrN_W0.2MPa shows the X-ray diffraction measurement result of the test piece obtained by projecting tungsten media at 0.2 MPa on the CrN hard film, CrN shows the X-ray diffraction measurement result of the CrN hard film after film formation (untreated: the particle projection treatment is untreated), and WC-Co shows the X-ray diffraction measurement result of the cemented carbide (equivalent to K10) of the substrate. From these facts, it is considered that the crystallinity of the hard films (TiN, CrN) has changed due to the particulate projection treatment according to the present embodiment.

[0048] From the measurement results shown in FIG. 5, peaks that cannot be identified from the spectra of TiN, CrN, and the cemented carbide of the base material have been detected after film formation. These disappear or the peak intensity weakens due to the particulate projection treatment. That is, an unstable phase (meta-stable phase) that does not crystallize exists in the hard thin film formed in a non-equilibrium state (in plasma). This is considered to be the cause of the unidentifiable peak. The fact that the unidentifiable peak disappeared and the intensity decreased due to the particulate projection treatment is considered to be due to the crystallization of the meta-stable phase. And, due to the change (stabilization) of the crystallinity of the hard films (TiN, CrN), the defective portions of the hard films (TiN, CrN) disappear, which is considered to contribute to suppressing the occurrence of defects, breakage, peeling, etc. of the hard films (TiN, CrN).

[0049] That is, also from this point, in the present embodiment, it is possible to contribute to strengthening both the base material surface and the hard film of a member in which a hard film (for example, TiN, CrN, etc.) is formed on the surface of a sintered composite material (for example, cemented carbide, cermet, etc.) or alloy tool steel as the base material, and improving durability, wear resistance, etc.

[0050] In the present embodiment, high-speed steel (SKH51) has been described as an example. However, in addition to SKH51, there are SKH55, SKH57, SKH59, matrix high-speed steel, etc. for high-speed steel, and SKH51 is often used as a representative. Therefore, although SKH51 has been described representatively here, it is considered that the effects of the present invention are also similarly achieved in SKH55, SKH57, SKH59, matrix high-speed steel of the same type other than SKH51, and they are considered to belong to the application range of the present invention. Further, the present invention is also applicable to steels for cold forging dies, steels for hot forging dies, steels for plastic dies, etc. other than high-speed steel, and these are collectively referred to as alloy tool steel including high-speed steel.

[0051] Here, as disclosed in Japanese Patent Application Laid-Open No. 2019-183204 (Patent No. 6823303), under a concept that is completely different from or contrary to the conventional concept or approach method of increasing residual stress by colliding high-hardness media, for an object to be processed that is a sintered composite material such as cemented carbide or cermet, when performing a fine particle peening treatment (fine particle projection treatment) using a ductile metal material (a metal material having ductility) with a hardness lower than that of the object to be processed as a medium, even for a sintered composite material such as cemented carbide or cermet, since the compressive residual stress can be significantly increased, the applicant has obtained the knowledge that the fracture toughness and flexural strength can be improved. Furthermore, from the idea that it would be more excellent if the generation of surface defects could be effectively suppressed while simultaneously increasing the residual compressive stress, the applicant of the present application has conducted various studies, experiments, etc., and thereby, a metal material that has a hardness lower than that of the cemented carbide (for example, hardness: about 800 - 1800 Hv, about 92 - 93 HRA) which is the object to be processed (workpiece) and is one of the high-density (high specific gravity) metal materials, W (tungsten: average particle size φ4 μm: hardness: about 100 - 350 Hv, specific gravity 19.3 g / cm 3 )(hereinafter, the unit is omitted for the specific gravity) is projected (shot) as a medium, and has obtained the knowledge that this is extremely beneficial.

[0052] This embodiment, similar to Japanese Patent Application Laid-Open No. 2019-183204 (Patent No. 6823303), is based on the idea of effectively suppressing the generation of surface defects while simultaneously increasing the residual compressive stress. For a member having a hard film formed on the surface with a sintered composite material (e.g., cemented carbide, cermet, etc.) or alloy tool steel as the base material, when performing particle projection treatment (particle peening treatment) using a ductile metal material (a metal material having ductility) with a hardness lower than that of the base material as a medium, it was confirmed what kind of influence it has on the member having the hard film. According to the particle projection treatment according to this embodiment, as described above, it was confirmed that a good improvement effect was obtained even for tool steel having a hard film. Therefore, the content disclosed in Japanese Patent Application Laid-Open No. 2019-183204 (Patent No. 6823303) regarding the types of base materials and media is also applicable to the present invention.

[0053] Here, in Japanese Patent Application Laid-Open No. 2019-183204 (Patent No. 6823303), the measurement results of the residual stress when performing particle projection treatment (particle peening treatment) using various media, which are ductile metal materials with a hardness lower than that of the cemented carbide, which is the object to be treated (workpiece), are shown in FIG. 6.

[0054] FIG. 6 shows the experimental results (effects) when particle projection treatment (particle peening treatment) is performed on a cemented carbide (a general cemented carbide TH10, for example, hardness: about 800 - 1800 Hv, about 92 - 93 HRA). As shown in FIG. 6, the material, average particle size, hardness, etc. of the media used in the experiment are as follows. Regarding the hardness, it is often difficult to measure, and it is described as a nominal value. Symbol 1: Sn (material: tin), size classified by #280 (average particle size) = about φ48 μm, hardness: about Hv50 Symbol 2: Mo (molybdenum disulfide: MoS2), size classified by #280 (average particle size) = about φ48 μm, hardness: about Hv160 Symbol 3: SUS (stainless steel), size classified by #280 (average particle size) = about φ48 μm, hardness: about 500 Hv Symbol 4: SP (Conventional shot peening using large-sized steel (cast steel) as the medium), (average particle size) about φ0.8 mm, hardness: about 300 Hv Symbol 5: SS (cast steel), size classified by #280 = about φ48 μm (average particle size), hardness: about 300 Hv Symbol 6: H (high-speed steel, high-speed tool steel), size classified by #280 = about φ48 μm (average particle size), hardness: about 1000 Hv Symbol 7: B (SiO2: comparison data), size classified by #280 = about φ48 μm (average particle size), hardness: about 900 Hv Symbol 8: Ni (nickel), size classified by #280 = about φ48 μm (average particle size), hardness: about 200 Hv Symbol 9: W (tungsten), size classified by #3000 = about φ4 μm (average particle size), hardness: about 250 Hv

[0055] According to FIG. 6, it can be confirmed that in the case of particle projection treatment using a ductile metal material (for example, SUS (stainless steel), cast steel, H (high-speed steel), Ni (nickel), etc.) with a hardness lower than that of the cemented carbide which is the object to be treated, a compressive residual stress can be imparted to the surface of the cemented carbide by using a medium (average particle size about φ48 μm).

[0056] On the other hand, when W (tungsten: average particle size about φ4 μm: hardness: about 250 Hv) with a high specific gravity (high density) is used as the medium, it can be confirmed that the compressive residual stress when applied to a general cemented carbide (TH10, hardness: about 800 - 1800 Hv) is extremely large at -1600 GPa compared with the conventional method.

[0057] However, since the hardness varies widely depending on the heat treatment conditions and microstructure, it is considered that even with hardness values other than those mentioned above, similar effects may be achieved in some cases.

[0058] Furthermore, from the results of surface observation of the object to be processed when using W (tungsten: average particle size of about φ4 μm: hardness: about 250 Hv) as the medium, compared with the case of using high-hardness materials such as glass beads and ceramics as the medium, no surface defects (scratches) were observed on the surface of the object to be processed. It was found that by using a particulate projection process with a medium having a lower hardness than the object to be processed (the object to be treated), the generation of surface defects can be suppressed.

[0059] From the above, it is considered that the application of residual compressive stress (introduction of dislocations into crystals) has an effect (influence) on the distribution of the impact (shearing force) applied to the surface of the cemented carbide. And since it is considered that the distribution of the impact (shearing force) is greatly affected by the momentum (kinetic energy) of the medium, in the particulate projection process, it is considered that the specific gravity is effective for the application of residual compressive stress. Therefore, in addition to W (tungsten), other metal materials (including alloys, ductile metals, and brittle metals) with a specific gravity of 9 or more, such as molybdenum (specific gravity 10.28, hardness: about 160 Hv), lead (specific gravity 11.3), gold (specific gravity 19), and platinum (specific gravity 21), are also considered to be effective.

[0060] On the other hand, since it is considered that the surface damage (defects) are greatly affected by the hardness, it is considered that ductile materials are less likely to cause damage. Therefore, copper, tin (Sn), molybdenum disulfide (MoS2), etc. are also considered to be effective.

[0061] In addition, since the W (tungsten) used in this embodiment has an average particle size as small as about φ4 μm, it is difficult to ride on the ejection air and is slow even under the same conditions, so stress is applied but it is difficult to be damaged (because the particle size is small, the generated scratches are very tiny and are less likely to become surface defects that have a great impact on the flexural strength).

[0062] That is, regarding the base material according to the present embodiment (a member (tool steel) made of a sintered composite material (e.g., cemented carbide, cermet, etc.) or high-speed steel), it is an approach from a direction completely different from or contrary to the conventional concept or approach method of applying distortion to the surface of the object to be processed using hard ceramics with high hardness to increase the compressive residual stress (a ductile metal material with a hardness of Hv500 or less, such as SUS (stainless steel), copper, molybdenum disulfide, iron, Ni (nickel), Cr, etc., which is lower in hardness than the base material of the object to be processed that is a sintered composite material such as cemented carbide, or a compound mainly composed of these as a medium for particle projection treatment). By applying compressive residual stress, it is considered that the fracture toughness and flexural strength can be improved.

[0063] In addition, regarding the base material according to the present embodiment (a member (tool steel) made of a sintered composite material (e.g., cemented carbide, cermet, etc.) or high-speed steel), it is also an approach from a direction completely different from or contrary to the conventional concept or approach method of applying distortion to the surface of the object to be processed using hard ceramics with high hardness to increase the compressive residual stress (a metal material with a hardness lower than that of the base material of the object to be processed that is a sintered composite material such as cemented carbide and a high specific gravity (high density) (specific gravity of 9 or more), such as tungsten, molybdenum (specific gravity of 10.28, hardness: about 160 Hv), etc., as a medium (average particle size of, for example, about φ1.2 μm (#8000) to φ9.5 μm (#1200)) for shot peening treatment of fine particles). By this method, while effectively suppressing the generation of surface defects, compressive residual stress can be applied, and thus it is considered that the fracture toughness and flexural strength can be improved at a higher level.

[0064] That is, in the present embodiment, when a member (tool steel) made of a sintered composite material (e.g., cemented carbide, cermet, etc.) or high-speed steel is used as a base material and a hard film is formed on its surface as an object to be treated, a fine particle medium having a hardness lower than that of the base material of the object to be treated and being Hv500 or less, for example, any one of stainless steel, copper, molybdenum disulfide, iron, nickel, chromium, or a compound mainly composed of any of these, or a fine particle medium in which at least two of these are mixed is used to perform fine particle projection treatment in the range of an injection speed of 100 to 200 m / sec, it is considered that the fracture toughness and flexural strength can be improved.

[0065] Further, in the present embodiment, when a member (tool steel) made of a sintered composite material (e.g., cemented carbide, cermet, etc.) or high-speed steel is used as a base material and a hard film is formed on its surface as an object to be treated, tungsten, molybdenum, or a metal material having a specific gravity of 9 g / cm 3 or more, or a compound mainly composed of any of these, or a fine particle medium in which at least two of these are mixed is used to perform fine particle projection treatment in the range of an injection speed of 100 to 200 m / sec, it is possible to apply compressive residual stress while effectively suppressing the generation of surface defects, and thus it is considered that the fracture toughness and flexural strength can be improved at a higher level.

[0066] Also, in the present embodiment, titanium nitride (TiN) and chromium nitride (CrN) are exemplified as the hard thin film (hard coating), but the present invention is not limited thereto. TiN and CrN are the basis of hard coatings, but new functions can be created by adding additive elements thereto, and these can also be included in the scope of the present invention. For example, the following coatings have been developed at present. TiN: TiCN, TiAl(C)N, TiSi(C)N, TiAlSi(C)N, TiB(C)N, TiAlNbN, TiAlVN, etc. can also be included in the scope of the present invention as hard films (TiN-based hard films) based on TiN. CrN:CrCN, CrAlcN, CrSi(C)N, CrAlSi(C)N, CrB(C)N, etc. can also be included in the scope of the present invention as hard films based on CrN (CrN-based hard films). In addition, hard films obtained by fusing TiN and CrN, such as TiCrN, TiCr(C)N, TiCrAl(C)N, TiCrSi(C)N, TiCrAlSi(C)N, etc., can also be included in the scope of the present invention.

[0067] That is, according to the present embodiment, a surface treatment method of a member that can strengthen both the base material surface and the hard film of a member formed by forming a hard film (hard film of titanium nitride (TiN), hard film of chromium nitride (CrN), hard film based on CrN, hard film based on TiN, or hard film obtained by fusing TiN and CrN, etc.) on the surface of a sintered composite material (e.g., cemented carbide, cermet, etc.) or alloy tool steel as a base material, and can improve durability, wear resistance, etc., and a tool steel with a hard film whose durability, wear resistance, etc. are improved by the surface treatment method can be provided.

[0068] In addition, in the present embodiment, the case where 3 μm of titanium nitride (TiN) and chromium nitride (CrN) are respectively formed is exemplified, but the present invention is not limited thereto. The present invention is applicable when the film thickness is 3 μm or less, and further, the functions and effects of the present invention are also achieved within the normal film thickness range formed as a hard thin film, that is, in the range of 0.5 μm to 10.0 μm. Therefore, the range of the film thickness of the hard thin film being 0.5 μm to 10.0 μm can be set as the application range of the present invention.

[0069] Note that the tool steel (member) with a hard film according to the present embodiment can be used for cutting tools (drills, end mills, reamers, taps, bits, cutters, hob cutters, pinion cutters, broaches, round blades, chip saws, throw-away tips, etc.), and it is beneficial as its durability, wear resistance, etc. are improved. In addition, the tool steel (member) with a hard film according to the present embodiment can be used for die tools (cold forging dies, warm forging dies, hot forging dies, die-casting dies, resin molding dies, rolling tools, punches, dies, etc.), mandrels, etc., and is beneficial as its durability, wear resistance, etc. are improved. In addition, the tool steel (member) with a hard film according to the present embodiment can be used for machine parts (pins, guides, chutes, hoppers, gears, shafts, rollers, etc.), and is beneficial as its durability, wear resistance, etc. are improved.

[0070] Here, cemented carbides refer to nine metals belonging to Groups 4, 5, and 6 of the periodic table (titanium <ti>, Vanadium <v>, chromium <cr>, zirconium <zr>, Niobium <nb>, Molybdenum , Hafnium <hf>, Tantalum <ta>, tungsten <w>) It is a general term for alloys obtained by sintering and bonding carbide powders with iron-group metals such as iron (Fe), cobalt (Co), and nickel (Ni). Among them, the WC-Co alloy, which combines tungsten carbide (WC) and Co, has extremely excellent properties, and generally refers to the WC-Co alloy. In a broad sense, it may include cemented carbides, ceramics, sintered diamond and other hard tool materials. Here, the WC-Co alloy is regarded as a cemented carbide. Cemented carbides are relatively new materials, having been developed for more than 100 years, and it is said that no alloy has been born that surpasses the combination of WC and Co so far. The main component of cemented carbide is WC particles, which are hard particles, and Co filling the space between the particles is used as a binder for WC particles.

[0071] In addition, cemented carbide is a composite material obtained by mixing powders of hard compounds such as metal carbides and nitrides with a metal binder and sintering them. By definition, it also includes those with tungsten carbide (WC) as the main component, which are called cemented carbides, but they are often treated as separate materials. The name is a coined word from ceramics and metal. It was developed in 1959 as a tool material with slightly greater toughness than ceramics. As for the characteristics of cemented carbide, generally, it has high heat resistance and wear resistance, but it is brittle and prone to chipping. It is mainly used as a material for cutting tools, and is also used for parts of machinery in chemical plants and nozzles for high temperatures. As an example of the composition (wt%), TiC -20 TiN -15 WC -10 Mo2C -5 Ni can be mentioned.

[0072] In addition, as a cemented carbide for cutting tool materials, those mainly combining titanium compounds such as titanium carbide (TiC) and titanium carbonitride (TiCN) with nickel (Ni) or cobalt (Co) are often used. Such titanium-based cemented carbides have a lower affinity with iron compared to cemented carbides and are particularly effective in the finish cutting of steel. In addition, niobium carbide (NbC) and others are also used as hard compounds.

[0073] Next, the particle projection process (particle peening process, WPC process) will be described. The particle projection process is a surface treatment also known as the WPC (Wide Peening and Cleaning) process, "particle peening" process, "precision shot peening" process, "FPB (Fine Particle Bombarding)" process, etc. It is a surface modification process in which particles are mixed with a compressible gas and made to collide at high speed with the surface of a member.

[0074] Note that as the particle projection process, for example, the heat treatment method (WPC process) of metal products described in Patent No. 5341971 can be applied. Specifically, it is performed by injecting media (shots, particles with a small particle size) from the following injection device and causing them to collide with the object to be treated.

[0075] 〔Injection device〕 The WPC process according to the present invention injects media (shots) by a known blasting device and causes them to collide with the surface of a metal product.

[0076] For example, as an air-type blasting device, various types can be used. For example, a direct-pressure blasting device that supplies compressed air into a tank filled with shots and rides the shots conveyed by the compressed air on an air stream of separately supplied compressed air and injects them from a blasting gun, a gravity-type blasting device that rides the shots that have fallen from the tank on compressed air and injects them, a suction-type blasting device that sucks the shots by the negative pressure generated by the injection of compressed air and injects them together with the compressed air, and various other blasting devices can be used.

[0077] 〔Media (shots)〕 The media (shots) used in the present invention have a hardness lower than that of the base material of the object to be processed, and the average particle size is, for example, in the range of several μm to several tens of μm, and three or more approximate particle sizes can be mixed according to the purpose. The approximate particle size refers to the particle size within the above range.

[0078] Then, by using the injection device as described above, a group of media (shots) is mixed with compressed air, and intermittent injection is performed for 0.1 to 1 second at an injection pressure of about 0.3 to 0.6 MPa, an injection speed of about 100 to 200 m / s, and an injection distance of about 50 mm to 250 mm. That is, injection for 0, 1 to 1 second is preferably repeatedly injected at intervals of 0.5 seconds to 5 seconds to collide with the surface of the object to be processed in the WPC treatment.

[0079] In addition, in this embodiment, cemented carbide and cermet have been typically described, but the present invention is not limited thereto, and even for sintered composite materials obtained by mixing and sintering powders of hard compounds such as metal carbides and nitrides with a metal binder other than cemented carbide and cermet, the concept of the present invention is applicable.

[0080] Also, as shown in FIG. 6, it has been confirmed that a ductile metal material having a hardness lower than that of the base material of the object to be processed (for example, high-speed tool steel (HSS), cast steel, etc.) or a high-density metal material having a hardness lower than that of the base material of the object to be processed (for example, tungsten) has a high surface modification effect on the sintered composite material. However, as the media used for the fine particle projection treatment, not only when any one of these is used alone, but also a combination (mixture) of at least two of these can be used as the media.

[0081] By the way, in the present embodiment, a ductile metal material having a lower hardness than the base material of the object to be processed has been described as the particulate medium in the particulate peening process. However, when it is difficult for the ductile metal material to remain as it is in the presence of air, or when it changes under the influence of heat or the like during the particulate peening process, a compound (such as an oxide) containing the ductile metal material as the main component can also be used as the particulate medium.

[0082] Also, in the present embodiment, a metal material having a lower hardness than the base material of the object to be processed and a high density has been described as the particulate medium in the particulate projection process. However, when it is difficult for the ductile metal material to remain as it is in the presence of air, or when it changes under the influence of heat or the like during the particulate peening process, a compound (such as an oxide) containing the ductile metal material as the main component can also be used as the particulate medium.

[0083] The present invention is not limited to the above-described embodiments of the invention, and various modifications can be made without departing from the gist of the present invention.< / w> < / ta> < / hf> < / nb> < / zr> < / cr> < / v> < / ti>

Claims

1. A method for surface treatment of a member, comprising: using a particulate medium made of a ductile metal material having a hardness of 500 Hv or less, which is lower than the hardness of the base material of the member, or a compound thereof, to perform a particulate projection treatment on a member having a hard film formed on the surface of a sintered composite material or alloy tool steel as the base material.

2. The method for surface treatment of a member according to claim 1, wherein the particulate medium is any one of stainless steel, copper, molybdenum disulfide, iron, nickel, chromium, or a compound having any of these as a main component, or a particulate medium obtained by mixing at least two of these.

3. For a member having a sintered composite material or alloy tool steel as a base material and a hard film formed on the surface of the base material, tungsten, molybdenum, or a metal material with a specific gravity of 9 g / cm ３ or more, or any of compounds mainly composed of these, or a particulate medium in which at least two of these are mixed is used to perform a particulate projection treatment. A surface treatment method for a member, characterized by this.

4. The method for surface treatment of a member according to any one of claims 1 to 3, wherein the hard film is a hard film based on TiN, a hard film based on CrN, or a hard film obtained by fusing TiN and CrN.

5. The method for surface treatment of a member according to any one of claims 1 to 3, wherein the sintered composite material is a cemented carbide or cermet.

6. The method for surface treatment of a member according to claim 5, wherein the cemented carbide is a WC-Co based alloy.

7. The method for surface treatment of a member according to any one of claims 1 to 3, wherein the alloy tool steel is a high-speed tool steel.

8. A tool steel with a hard film produced by using the method for surface treatment of a member according to any one of claims 1 to 3.

9. A member having a hard film formed on the surface of a sintered composite material or alloy tool steel as the base material, wherein a particulate projection treatment is performed on the surface thereof using a particulate medium made of a ductile metal material having a hardness of 500 Hv or less, which is lower than the hardness of the base material of the member, or a compound thereof.

10. The member according to claim 9, wherein the particulate medium is any one of stainless steel, copper, molybdenum disulfide, iron, nickel, chromium, or a compound having any of these as a main component, or a particulate medium obtained by mixing at least two of these.

11. A member having a sintered composite material or alloy tool steel as a base material and a hard film formed on the surface of the base material, and on the surface thereof, tungsten, molybdenum, or a specific gravity of 9 g / cm ３ or more of any of these metal materials, or any of compounds having these as main components, or a particulate medium obtained by mixing at least two of these, and being subjected to a particulate projection treatment.

12. The member according to any one of claims 9 to 11, wherein the hard film is a hard film based on TiN, a hard film based on CrN, or a hard film obtained by fusing TiN and CrN.

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