CN103157815B - Surface-coated cutting tools exhibit excellent wear resistance in high-speed heavy cutting - Google Patents

Abstract

The present invention provides a kind of surface coating layer cutting element, and its hard coating layer, in the high speed heavy cut of cast iron, carbon steel etc. is processed, plays the lubricity of excellence, wearability.The surface-coated cutting tool of the present invention, at least most surface in tool base possesses and has the average thickness of 0.2～5 μm and the higher alumina layer of flatness, this alumina layer is made up of substrate and the spheroidal structure that is dispersed in substrate, above-mentioned substrate is made up of alumina crystalline phase and amorphous phase, and, above-mentioned spheroidal structure is made up of the aggregation of one or both in needle-like crystalline phase and tabular crystalline phase and amorphous phase, area ratio shared by the spheroidal structure of the longitudinal section being contained in alumina layer is 20～60 area %, and the radius of approximate circle is 0.02～0.5 μm.

Description

Surface-coated cutting tools exhibit excellent wear resistance in high-speed heavy cutting

technical field

The present invention relates to a surface-coated cutting tool whose hard coating has excellent surface smoothness, lubricity, chip discharge, and welding resistance, so it can be used for high-speed heavy cutting of cast iron, carbon steel, etc. When processing, it exhibits excellent wear resistance even after long-term use.

Background technique

As is known to all, hard coatings consisting of carbides, nitrides, and carbonitrides of at least one element selected from groups 4a, 5a, and 6a in the periodic table have been formed on the surface of the tool substrate to achieve Improvement of wear resistance of cutting tools.

In addition, in the hard film, especially the α-type alumina layer has good thermal stability, low reactivity, and high hardness, so as an element composed of at least one or more elements selected from the 4a, 5a, and 6a groups in the above-mentioned periodic table The outermost layer of the hard film composed of carbides, nitrides, and carbonitrides is usually coated to form an α-type alumina layer.

As a method for coating and forming an alumina layer, a chemical vapor deposition (CVD) method is generally used, and it is also known to form an alumina layer by a physical vapor deposition (PVD) method and a sol-gel method.

For example, as shown in Patent Document 1, in order to avoid deterioration/deformation of the properties of the tool base and the hard coating, as a method of forming an α-alumina layer at a low temperature (below 1000°C), the following content is proposed. Vapor deposition method (PVD) forms nitrides, carbides, carbonitrides, and borides on the surface of the tool substrate, which are composed of A1 and at least one element selected from group 4a, group 5a, group 6a and Si. , nitrogen oxide, and carbonitride hard film, the hard film is oxidized to form an oxide-containing layer, and the oxide-containing layer is vapor-deposited by physical vapor deposition (PVD) as the outermost layer The α-type crystal structure with excellent wear resistance and heat resistance is used as the main alumina layer.

Furthermore, as shown in Patent Document 2, it is proposed that in a surface-coated cutting tool in which a hard coating layer is formed by physical vapor deposition (PVD) deposition, the first layer is formed of a (Ti, Al)N layer, and The second layer is composed of an alumina layer (preferably a gamma alumina layer).

In addition, as shown in Patent Document 3, as a method of producing an alumina-coated structure having mechanical properties and durability, it has been proposed to change the crystal structure into an amorphous structure or γ-type alumina by a sol-gel method, or a combination thereof. After coating the base material with the first alumina layer composed of a mixture of the above, the second alumina layer mainly composed of gamma type is formed by sputtering coating.

Patent Document 1: Japanese Patent Laid-Open No. 2004-124246

Patent Document 2: Japanese Patent Laid-Open No. 2007-75990

Patent Document 3: Japanese Patent Laid-Open No. 2006-205558

Surface-coated cutting tools that form an aluminum oxide layer as a hard coating layer by CVD method can improve the wear resistance of the rake face of the coated tool when cutting cast iron, steel, etc., which is especially It is obtained because α-type alumina has high thermal stability and non-reactivity.

In the above-mentioned Patent Document 1, it is proposed to form an α-type alumina layer under low temperature conditions by physical vapor deposition (PVD). However, since the adhesion between the oxide-containing layer and the alumina layer is insufficient, and there are not only α-type alumina but also γ-type alumina as alumina, sufficient heat resistance cannot be obtained. There is a problem that satisfactory cutting performance cannot be exerted by use.

In addition, in the above-mentioned Patent Documents 2 and 3, the alumina formed is γ-type alumina, so it lacks stability at high temperatures, and there is a problem that satisfactory cutting performance cannot be exhibited in high-speed cutting.

Contents of the invention

Therefore, the inventors of the present invention conducted intensive studies to form an aluminum oxide layer excellent in wear resistance on the surface of the tool substrate by the sol-gel method, and found that: , Dispersion and distribution of a spherical structure with excellent wear resistance composed of one or two of the needle-like crystal phase and the plate-like crystal phase and the aggregate of the amorphous phase, when used to generate high heat, and high load acts on the cutting edge Even in high-speed heavy-duty cutting, it is possible to obtain a surface-coated cutting tool with excellent wear resistance.

That is, it has been found that when preparing alumina sol, stirring at a lower temperature than usual and holding for a long time as a low-temperature aging treatment suppresses the reaction rate of hydrolysis and polycondensation, and densely forms Al-O bonds. When the alumina precursor is formed, more octahedral AlO ₆ close to the corundum structure can be formed. Therefore, if the alumina sol is applied as the surface layer of the tool substrate and dried and fired, the following oxidation can be formed: The surface layer of the hard film composed of an aluminum layer. The above-mentioned alumina layer is a matrix of alumina with high smoothness, lubricity, and excellent welding resistance to chips. The needle-like crystal phase and plate One or two of the crystalline phases and aggregates of the amorphous phase form a spherical structure of alumina with excellent wear resistance.

In addition, when the hard film adjacent to the aluminum oxide layer of the surface layer is formed as a nitride film in which Al accounts for 40 atomic % or more in the metal composition of the hard film, due to the contact with the surface layer, The adhesion strength of the alumina layer is increased, and it is preferable from the viewpoint of suppressing the peeling of the alumina layer, the occurrence of chipping, etc. due to impacts during cutting, and the like.

That is, it was found that in the surface-coated cutting tool of the present invention, the surface layer of the hard coating layer is composed of an alumina layer, and the alumina layer is composed of alumina excellent in smoothness, lubricity, and welding resistance. The matrix is composed of a spherical structure with excellent wear resistance dispersed in the matrix. Therefore, when the surface-coated cutting tool with this hard coating layer is used for high-speed heavy cutting of cast iron and carbon steel, it will last for a long time. Exhibits excellent wear resistance over time.

The present invention has been accomplished based on the above findings, and is characterized in that,

(1) A surface-coated cutting tool, which is formed by coating the surface of a tool substrate composed of tungsten carbide-based cemented carbide and titanium carbonitride-based cermet to form a hard coating layer, characterized in that,

(a) having an aluminum oxide layer having an average layer thickness of 0.2 to 5 μm as a surface layer of the hard coating layer,

(b) The above-mentioned alumina layer is composed of a matrix and spherical structures dispersed in the matrix,

(c) The above-mentioned matrix is composed of an alumina crystal phase and an amorphous phase, and the above-mentioned globular structure is composed of one or both of the needle-like crystal phase and the plate-like crystal phase and an aggregate of the amorphous phase.

(2) The surface-coated cutting tool according to (1), wherein the spherical structure occupies an area ratio of 20 to 60 area % in the alumina layer.

(3) The surface-coated cutting tool according to (2) above, wherein the radius of the approximate circle of the spherical structure is 0.02 to 0.5 μm.

(4) The surface-coated cutting tool as described in any one of (1) to (3), which forms a hard coating layer on the surface of the tool substrate composed of tungsten carbide-based cemented carbide. into, characterized in that,

A base hardened layer having an average layer thickness of 0.5 to 3.0 μm is formed from the surface of the tool base toward the depth direction, and the average content of Co as a binder phase metal contained in the base hardened layer is less than 2.0% by mass.

(5) The surface-coated cutting tool according to any one of claims (1) to (3), which forms a hard coating layer on the surface of the tool substrate composed of titanium carbonitride-based cermet. made, characterized in that,

A base surface hardened layer having an average layer thickness of 0.5 to 3.0 μm is formed from the surface of the above-mentioned tool base toward the depth direction, and the total average content of Co and Ni as a binder phase metal contained in the base surface hardened layer is less than 2.0 mass %.

The present invention will be described in detail below.

The surface-coated cutting tool of the present invention has an aluminum oxide layer formed by a sol-gel method of 0.2 to 5.0 μm as the surface layer of the hard coating layer, but if the thickness of the aluminum oxide layer is less than 0.2 μm, the subsequent The number of the above-mentioned spherical structures is small, so sufficient wear resistance cannot be exerted. On the other hand, if the layer thickness exceeds 5.0 μm, the layer peeling will easily occur, so the layer thickness of the aluminum oxide layer is set at 0.2 to 5.0 μm. μm.

In addition, the above-mentioned aluminum oxide layer can exert its performance by directly forming a film on the tool substrate, but when using a tungsten carbide-based cemented carbide containing titanium carbonitride as the substrate, Ti can be formed by firing in a nitrogen atmosphere. , Ta, Nb, Zr at least one carbonitride with high wear resistance contains more near the surface of the tool substrate, thereby forming a hardened layer on the surface of the substrate, which can improve the adhesion strength between the aluminum oxide layer and the tool substrate, Extend tool life. In addition, the hardness of the cemented carbide substrate after forming the surface hardened layer of the substrate is preferably 2200 or more and 2800 or less in terms of Vickers hardness (Hv). At this time, by containing more carbonitrides, the Co near the surface of the substrate can be relatively reduced. For example, use a scanning electron microscope (SEM) to observe a section from the surface to 0.5-3.0 μm in the depth direction, and analyze it in the field of view. When the content of Co as a binder phase metal is detected by quantitative analysis based on wavelength dispersive X-ray spectrometry in the range of 1×1 μm, if the content of Co is less than 2.0% by mass, it is sufficiently formed and becomes the main cause of surface hardening of the matrix. Carbonitrides further improve wear resistance.

If the average layer thickness of the surface hardened layer of the base body is 0.5 μm or less, the wear resistance will not be fully exhibited, and it will be worn early, and if it is 3.0 μm or more, the blade will be easily broken.

In addition, when titanium carbonitride-based cermets are used as the substrate, the atmosphere during the sintering process when the temperature is raised and held at the highest temperature is set to a predetermined nitrogen atmosphere, and the pressure is reduced during the holding or when the temperature is lowered, thereby Compared with the case where the entire sintering process is carried out in a nitrogen atmosphere at a constant pressure, the surface can be hardened. This is because if the process is carried out under a certain nitrogen pressure until the process is held at the highest temperature, carbonitrides with high hardness are uniformly dispersed and formed in the collective, but if the temperature is raised or held halfway, it is processed under a higher nitrogen pressure. , and in the middle of the maintenance or when the temperature is lowered, when the nitrogen atmosphere is further reduced, since the nitrogen is only denitrified on the outermost surface of the substrate, the melting of Ti and Nb to the Ni and Co metal bonding phase and the self-dissolution Diffusion from the inside to the surface of the substrate becomes active, and the formation of carbonitrides such as Ti and Nb is promoted on the surface, thereby forming a hardened layer on the surface of the substrate. In addition, the hardness of the cermet substrate after forming the surface hardened layer of the substrate is preferably 2000 or more and 2600 or less in terms of Vickers hardness (Hv). In addition, at this time, similarly to the above-mentioned tool base, Ni and Co near the base surface are relatively reduced, and if the content of Ni and Co as a binder phase metal is less than 2.0% by mass, carbon nitrogen, which is a main cause of base surface hardening, is sufficiently formed. compounds to further improve wear resistance.

When the average layer thickness of the hardened layer on the surface of the substrate is 0.5 μm or less as in the above-mentioned cemented carbide substrate, the wear resistance will not be fully exhibited, and the wear resistance will be worn early, and if it is 3.0 μm or more, the tool will be easily broken.

In addition, in the surface-coated cutting tool of the present invention, the above-mentioned alumina may not be directly formed on the surface of the tool substrate, but may be formed by physical vapor deposition (PVD) method, chemical vapor deposition (CVD) method, or sol-gel method. The hard coating known to those skilled in the art, that is, after more than one hard coating composed of nitrides or oxides containing at least one element selected from Groups 4a, 5a, 6a and Si in the periodic table , forming the above-mentioned aluminum oxide layer on the surface layer of the hard film.

In addition, when the hard film is formed by the above-mentioned physical vapor deposition (PVD) method, for the hard film adjacent to the aluminum oxide layer, it is preferable to form the hard film containing Al, and the nitride film (for example, TiAlN film, CrAlN film, etc.) in which Al accounts for 40 atomic % or more in the metal composition of the hard film.

This is because, in the case of a nitride film in which Al accounts for 40 atomic % or more in the metal composition of the hard film, an oxide layer with a high aluminum concentration is formed at the interface between the nitride film and the aluminum oxide film. As a result, the oxide has the effect of firmly bonding the nitride film and the aluminum oxide film.

The aluminum oxide layer constituting the surface layer of the surface-coated cutting tool of the present invention is formed by the sol-gel method described later, whereby its matrix is composed of an alumina crystal phase and an amorphous phase, and the aluminum oxide layer is formed in the matrix. A spherical structure composed of one or both of the needle-like crystal phase and the plate-like crystal phase and the aggregate of the amorphous phase.

Regarding the above-mentioned spherical structure, when the aluminum oxide layer is observed by a scanning electron microscope (SEM), as shown in Figure 1 and Figure 2, a spherical aggregate structure with a radius of 0.02-0.5 μm is observed, and if the aluminum oxide layer is observed by a transmission electron microscope (TEM) Further observation of the spherical structure reveals that an aggregate structure of an amorphous phase, a needle crystal phase, and a plate crystal phase is formed.

Furthermore, the area ratio of the spherical structure in the alumina is found to be 20 to 60 area % by observing the vertical cross-section SEM within a field of view area of 5×7 μm, for example.

In addition, according to FIG. 2 , it can be seen that a concave portion is formed at the interface between the spherical structure and the alumina in the matrix so as to surround the spherical structure (in FIG. 2 , a black ring-shaped portion).

The shape of the spherical structure is originally a composite structure in which the phases are arranged in various directions, so it has strong isotropy, and its stress dispersion effect contributes to stable wear resistance even in heavy cutting with a high load . If the area ratio of the above-mentioned spherical structure in alumina exceeds 60 area%, the proportion of the matrix fixing the spherical structure will become smaller, so the alumina layer will tend to be brittle, and the concave portion surrounding the spherical structure (refer to Figure 2 ) ratio becomes large, and a non-uniform load acts on the layer during cutting, which may cause damage. On the other hand, when the area ratio is less than 20 area%, the wear resistance of the alumina layer decreases because the spherical structure contributing to the improvement of wear resistance decreases.

Therefore, in the present invention, the area ratio of the spherical structure in the alumina layer is set at 20 to 60 area %.

When the radius of the spherical structure is obtained as a radius of a circle having an area equal to the area of the spherical structure, if the radius is less than 0.02 μm, the effect of improving the wear resistance in the alumina layer becomes small. On the other hand, When the radius exceeds 0.5 μm, the structure becomes coarse, which tends to cause cracks and lower the chipping resistance.

Therefore, the size of the above-mentioned spherical structure is set at a radius of 0.02 to 0.5 μm.

The alumina layer constituting the surface layer of the surface-coated cutting tool of the present invention can be formed by the sol-gel method described below.

Preparation of alumina sol:

First, add alcohol (such as ethanol, 1-butanol) to aluminum alkoxide (such as aluminum sec-butoxide, aluminum propoxide), and further add (also can add α-alumina particles with an average particle size of 10-300nm at the same time) ) acid (for example, hydrochloric acid, nitric acid), stirring in a temperature range of 15 to 30° C., and performing an aging treatment for, for example, 12 hours or more to form an alumina sol.

In addition, when adding alcohol, it is preferable to add α Alcohol of alumina particles. In addition, this is because the α-alumina particles become nuclei serving as the starting point of crystal growth at the time of coating, and have the effect of forming a spherical aggregate structure with a uniform diameter and a good dispersion in the alumina layer around this, but adding In the case of alcohol containing α-alumina particles, if the average particle size of α-alumina particles is less than 10 nm, the critical nucleus size that can become the starting point of crystal growth cannot be reached, so crystals do not form from the alumina sol around the α-alumina particles grows and is isolated from the matrix, and tends to become a site with weak bonding force with the surrounding crystal grains after firing. On the other hand, if the average particle size exceeds 300 nm, the crystal nuclei starting from the α-alumina particles will grow into excessively coarse particles, which will induce a decrease in film hardness and defects in the film. Therefore, the added α-alumina particles The average radius is set at 10 to 300 nm.

In addition, if the content of the α-alumina particles in the alcohol is less than 0.5% by mass relative to the aluminum alkoxide, the number of nuclei required to uniformly distribute crystal nuclei above a certain density in the film cannot be satisfied, and the crystallinity in the film cannot be satisfied. Since it is not uniform depending on the position, it is easy to induce abnormal wear during cutting. If the alkoxide relative to aluminum exceeds 5% by mass, the aggregation of α-alumina particles is likely to occur in the alumina sol, and when the alumina layer is formed, the aggregation part is formed as a coarse particle in the film, which induces defects in the film. From this reason, it is preferable to set the added amount of the α-alumina particles within a range of 0.5 to 5% by mass relative to the aluminum alkoxide.

Furthermore, the concentration of the added acid is preferably 0.01 to 4.0 N, and the amount of acid added is preferably 0.5 to 5 times (capacity) relative to the alcohol.

In the usual production of alumina sol, stirring at 40 to 80° C. and aging treatment at the stirring temperature for several hours are performed, but in the present invention, it takes a long time, for example, 12 hours or more. Low-temperature aging treatment with stirring in the low temperature range of 15-30°C.

Among them, if the temperature at the time of stirring and holding exceeds 30°C, the hydrolysis and polycondensation reactions will proceed rapidly, so the precursor cannot be densely formed, and α-alumina will not be formed in the firing process as a subsequent process, so stirring and holding The upper limit of the temperature at this time is 30°C. On the other hand, if the temperature at the time of stirring and holding is lower than 15°C, a plurality of densely structured Al-O junctions will be uniformly formed in the alumina sol, but it is necessary to form a The spherical structure of the size of the present invention is better to locally form a small amount of tight Al-O joints in the alumina sol, so the temperature during stirring and holding is set at 15-15°C where hydrolysis and polycondensation reactions are easily carried out locally. Low temperature range of 30°C.

In addition, the aging time is set to a long time of 12 hours or more because the hydrolysis is gradually promoted at low temperature, and the alumina precursor is formed densely.

Drying/Firing:

Apply the alumina sol prepared above directly to the surface of the tool substrate or to the outermost surface of the hard film formed on the surface of the tool substrate by physical vapor deposition (PVD), and then repeat the process for more than 100 times. ~400°C, more preferably drying treatment at 250-350°C, followed by firing treatment at a temperature range of 750-1000°C to coat and form an alumina layer.

A dry sol of alumina is formed by the above-mentioned drying treatment, and an alumina layer based on the alumina crystalline phase and the amorphous phase is formed on the surface of the hard film by the subsequent firing treatment. At the same time, in the matrix, the One or both of the needle-like crystal phase and the plate-like crystal phase and the spherical organization formed by the aggregate of the amorphous phase are dispersed and distributed in the matrix to form.

The film thickness of the above-mentioned alumina layer depends on the coating thickness and the number of times of coating of the alumina sol. If the film thickness of the above-mentioned oxide layer formed by coating is less than 0.2 μm, it will not be able to perform well as a surface-coated cutting tool that has been used for a long time. On the other hand, if the film thickness exceeds 5.0 μm, the aluminum oxide layer is likely to peel off, so the film thickness of the above-mentioned aluminum oxide layer is set at 0.2 to 5.0 μm.

In addition, the reason why the temperature range of the drying treatment is 100 to 400°C, more preferably 250 to 350°C, and the temperature range of the firing treatment is 750 to 1000°C is that if the drying temperature is lower than 100°C, It cannot be fully dried, and if it exceeds 400°C, the volume shrinkage of the sol will proceed rapidly, and cracks will occur, and film peeling will easily occur. For the firing temperature, if it is lower than 750°C, it will not be possible to form crystallinity that is sufficient for heavy cutting. Therefore, the wear resistance is insufficient. On the other hand, if fired at a temperature exceeding 1000°C, cracks caused by the difference in expansion coefficient between the alumina layer and the substrate will be formed, and cemented carbide or metal will be formed. Oxidation of ceramic substrates, etc., does not show the advantages of low-temperature film formation.

According to the surface-coated cutting tool of the present invention, the outermost surface of the tool substrate is coated with alumina formed by a sol-gel method, but the formed alumina layer has excellent surface smoothness, lubricity, and durability. Therefore, when it is used for high-speed heavy cutting of cast iron and carbon steel that generate high heat and a high load acts on the cutting edge, there will be no abnormal damage such as chipping and peeling, and it will exhibit excellent durability after long-term use. Abrasive.

Description of drawings

FIG. 1 shows a photograph of the longitudinal section of the aluminum oxide layer observed by SEM for the tool 1 of the present invention.

Fig. 2 shows the surface SEM photo of the spherical structure dispersed in the aluminum oxide layer of the tool 1 of the present invention.

detailed description

Next, the present invention will be described more specifically based on examples.

[Example 1]

As raw material powders, fine-grained WC powder with an average particle size of 0.8 μm, medium-sized WC powder with an average particle size of 2 to 3 μm, and TiCN powder, ZrC powder, TaC powder, NbC powder, and Cr powder each with an average particle size of 1 to 3 μm were prepared. ₃ C ₂ powder and Co powder, mix these raw material powders with the predetermined compounding composition shown in Table 1, further add paraffin and mix in acetone with a ball mill for 24 hours, dry under reduced pressure and press to form a predetermined shape with a pressure of 98MPa. The green compact was vacuum sintered under the condition of maintaining a temperature of 1400°C for 1 hour in a vacuum of 5 Pa. After sintering, the cutting edge was subjected to R: 0.05mm edge grinding processing to manufacture an ISO· WC-based cemented carbide tool substrates A, B, a, b, C1, C2, C3, C4 and C5 of the blade shape specified in CNMG120408 (called tool substrates A, B, a, b, C1, C2, C3 , C4 and C5).

However, regarding the process of cooling to 1320°C after holding at 1400°C for 1 hour, the tool substrate C2 was carried out in a nitrogen atmosphere of 3.3kPa for 40 minutes, and the tool substrate C3 was carried out in a nitrogen atmosphere of 1kPa for 40 minutes. The base C4 was cooled in a nitrogen atmosphere of 2 kPa for 10 minutes, and the tool base C5 was cooled in a nitrogen atmosphere of 3.3 kPa for 120 minutes to harden the surface of the base.

Next, the lower layers were formed for the above-mentioned tool bases A to C5.

And, when forming the lower layer, the above-mentioned tool substrates a and b are loaded into the chemical vapor deposition device, and the film-forming conditions shown in Table 2 are used to form the TiN layer, TiCN layer, TiCO layer, and TiCNO layer with granular crystal structure. A Ti compound layer composed of a TiCN layer (hereinafter referred to as 1-TiCN) with a vertically grown crystalline structure was formed in advance with a film composition shown in Table 4 as an underlayer. On the other hand, the above-mentioned tool base A was loaded into an arc ion plating apparatus which is one of physical vapor deposition apparatuses, and an underlayer composed of a Ti _0.5 Al _0.5 N layer having a film thickness shown in Table 4 was formed in advance.

Furthermore, the aforementioned tool base B was similarly installed in an arc ion plating apparatus, and an underlayer composed of an Al _0.7 Cr _0.3 N layer having a film thickness shown in Table 4 was formed in advance.

On the other hand, the base layer was not particularly formed for the above-mentioned tool bases C1, C2, C3, C4, and C5.

On the other hand, preparation of an alumina sol for coating an alumina layer forming a surface layer of a hard coating layer by a sol-gel method was carried out as follows.

(a) First, the solution composition of each component in the reaction raw material is calculated in molar ratio as (aluminum sec-butoxide): (water): (ethanol): (hydrochloric acid) = 1: (40-60): 20: 0.8 After adding in the manner shown in Table 3, the alumina sol was prepared by stirring and maintaining in a constant temperature tank under the conditions shown in Table 3.

(b) Next, the above-mentioned alumina sol was coated on the surface of the lower layer of the above-mentioned tool substrates A to C5.

(c) Next, the above-mentioned alumina sol after dip coating was dried in the atmosphere under the conditions shown in Table 3, and then fired at 800° C. for 1 hour in the atmosphere, whereby the present invention The aluminum oxide layer (that is, in the matrix composed of aluminum oxide crystal phase and amorphous phase, the spherical shape composed of one or two of the needle crystal phase and the plate crystal phase and the aggregate of the amorphous phase is dispersedly distributed. The aluminum oxide layer of the structure) was coated and formed on the outermost surface, and the coated tools 1-12 of the present invention shown in Table 4 (referred to as tools 1-12 of the present invention) were manufactured.

For tools 1 to 12 of the present invention mentioned above, the results of observing the longitudinal section of the aluminum oxide layer through a scanning electron microscope (SEM) confirmed that the matrix is composed of alumina crystal phase and amorphous phase, and on the other hand, the aluminum oxide layer is dispersed and distributed in the matrix. The globular structure is composed of one or both of the needle-like crystal phase and the plate-like crystal phase and the aggregate of the amorphous phase. A transmission electron microscope (TEM) was used to confirm the crystal phase and amorphous phase of alumina, and the matrix and spherical structure were respectively analyzed by the selected area electron diffraction method, and clear electron diffraction patterns and halo patterns were obtained.

In FIG. 1, an SEM photograph of a longitudinal section of the aluminum oxide layer of the tool 1 according to the invention is shown as an example, and in FIG. 2, also for the tool 1 according to the invention, the spherical structure dispersed in its aluminum oxide matrix is shown SEM photographs of the surface. According to Figure 2, it can be determined that the spherical structure is composed of an amorphous phase and aggregates of needle-like crystals and plate-like crystals.

Regarding the aforementioned tools 1 to 12 of the present invention, the area ratio of the spherical structure in the longitudinal section of the aluminum oxide layer and the average radius of the spherical structure were measured with a scanning electron microscope (manufactured by Carl Zeiss, ultra55) at a field of view of 50,000 times. Observe, for the result, measure the area ratio of the spherical tissue assuming a plane, and measure the radius of the approximate circle when calculating the area of the spherical structure as a circle area at 5 points, and take the average value as the average size.

In addition, at the same time, the cross-sectional measurement of the average layer thickness of the alumina layer was performed using a scanning electron microscope, and the results all showed an average value (average value at 5 locations) that was substantially the same as the target layer thickness.

The measurement results are shown in Table 4.

Furthermore, regarding tools 1 to 12 of the above-mentioned invention in which an aluminum oxide layer is directly formed on a hard substrate without providing an underlayer, the Co content on the surface of the tool substrate was measured by using the wavelength of a scanning electron microscope (SEM). Dispersive X-ray spectrometry, in the longitudinal section observation field of the tool substrate, conducts surface analysis from the surface of the substrate to the depth direction of 0.5~3.0μm in the range of 1×1μm, quantitatively analyzes the five fields of view, and adopts the average value.

Table 4 shows the layer thickness of the hardfacing layer and the amount of binder phase metal in the hardfacing layer.

[Comparative example 1]

For comparison, a surface-coated cutting tool was manufactured by the following manufacturing method.

(a) In the same manner as in Example 1, the solution composition of each component in the reaction raw material is calculated as (aluminum sec-butoxide) in molar ratio: (water): (ethanol): (hydrochloric acid) = 1: (40-60 ):20:0.8 way to add.

(b) Next, differently from Example 1, the alumina sol was prepared by continuing stirring for 12 hours and aging for 24 hours while maintaining the thermostat temperature shown in Table 3.

(c) Next, the above-mentioned tool substrates A to D and the tool substrate C1 without special surface treatment were respectively formed with the Ti compound layer formed by the above-mentioned chemical vapor deposition method, the TiAlN layer and the AlCrN layer formed by the physical vapor deposition method. The surface of ~C5 was coated with the above-mentioned alumina sol.

(d) Next, dry the above-mentioned coated alumina sol in the atmosphere under the conditions shown in Table 3, and then repeat the coating and drying until the predetermined layer thickness is reached, and then dry it in the atmosphere at 800°C The firing treatment was performed for 1 hour, thereby manufacturing surface-coated cutting tools 1 to 9 of comparative examples shown in Table 4 (referred to as comparative example tools 1 to 9).

Regarding Comparative Examples 1 to 9, the results of observing the aluminum oxide layer with a scanning electron microscope (SEM) and a transmission electron microscope (TEM) confirmed that spherical structures were not dispersed in the film.

Next, a high-speed heavy-duty cutting test of nodular cast iron was carried out on the above-mentioned tools 1 to 12 of the present invention and tools 1 to 9 of comparative examples under the following conditions.

The wear state of each tool after the high-speed and high-depth cutting test of nodular cast iron under the following conditions (the usual cutting speed and depth of cut are 200m/min and 1.0mm respectively) was observed, and the wear amount of the flank was measured .

Workpiece: JIS·FCD600 round bar

Cutting speed: 380/min

Cutting depth: 2.0mm

Feed rate: 0.3mm/rev.

Cutting time: 5 minutes

These results are shown in Table 5.

Table 1

Table 2

table 3

Table 4

table 5

[Example 2]

(a) As raw material powders, TiCN (TiC/TiN=50/50 by mass ratio) powder, Mo ₂ C powder, NbC powder, TaC powder, WC powder, and Co powder each having an average particle diameter of 0.5 to 2 μm were prepared. and Ni powder, and these raw materials are combined into the predetermined compounding composition shown in Table 6. After wet mixing with a ball mill for 24 hours and drying, the compact is formed into a compact with a pressure of 98MPa, and the compact is placed in a nitrogen atmosphere of 1.3KPa. After sintering at a temperature of 1540°C for 1 hour, the cutting edge portion is subjected to R: 0.07mm edge grinding, thereby manufacturing a TiCN-based cermet tool base with an insert shape according to ISO standard CNMG190612 D, E, d, e, F1, F2, F3, F4, and F5 (referred to as tool bases D, E, d, e, F1, F2, F3, F4, and F5). However, for the tool base F2, after raising the temperature from room temperature to 1540°C at a rate of 0.2°C/min in a nitrogen atmosphere of 1.3kPa and keeping it for 30 minutes, it was set to a vacuum of 13Pa and kept at 1540°C for 30 minutes before cooling down. harden the surface. For the tool base F3, it has been raised in a vacuum of 13 Pa and kept at 1540 ° C for 60 minutes. After the tool base F4 is heated from room temperature to 1540 ° C in a nitrogen atmosphere of 1.3 kPa and kept for 30 minutes, it is set to a vacuum of 13 Pa and held for 30 minutes. It was further kept at 1540°C for 5 minutes. For the tool base F5, the temperature was raised from room temperature to 1540°C in a nitrogen atmosphere of 1.3kPa and kept for 30 minutes. Surface hardening.

Table 6

(b) Next, the lower layer was formed for the above-mentioned tool bases D to F5.

In addition, when forming the lower layer, the above-mentioned tool bases d and e were placed in a chemical vapor deposition device, and under the film formation conditions shown in Table 2, the base layer was formed in advance with the film composition of the Ti compound in Table 8. On the other hand, the above-mentioned tool base D was placed in an arc ion plating apparatus which is one of physical vapor deposition apparatuses, and an underlayer composed of a Ti _0.5 Al _0.5 N layer having a film thickness shown in Table 8 was formed in advance.

Furthermore, the aforementioned tool base E was similarly installed in an arc ion plating apparatus, and an underlayer composed of an Al _0.7 Cr _0.3 N layer having a film thickness shown in Table 8 was formed in advance.

On the other hand, the base layer was not particularly formed for the above-mentioned tool bases F1, F2, F3, F4, and F5.

Then, in the above-mentioned tool bases D, E, d, e formed with the base layer and the above-mentioned tool bases F1 ~ F5 without the base layer formed, the sol-gel process through the preparation conditions and drying conditions of Table 7 was performed in the same manner as in Example 1. The aluminum oxide layer is formed until the glue method reaches the predetermined target layer thickness.

Next, firing treatment was performed at 800° C. for 1 hour in the air, and coated tools 13 to 24 of the present invention shown in Table 8 (referred to as present invention tools 13 to 24 ) were produced.

For the tools 13-24 of the present invention mentioned above, the results of observing the longitudinal section of the aluminum oxide layer through a scanning electron microscope (SEM) confirmed that the matrix is composed of alumina crystal phase and amorphous phase, and on the other hand, the aluminum oxide layer is dispersed and distributed in the matrix. The globular structure is composed of one or both of the needle-like crystal phase and the plate-like crystal phase and the aggregate of the amorphous phase.

For the tools 13-24 of the present invention mentioned above, the area ratio of the spherical structure in the longitudinal section of the aluminum oxide layer and the average radius of the spherical structure are observed with a field of view of 50,000 times through a scanning electron microscope. For the results, it is assumed that The area ratio of the spherical tissue was measured on the plane, and the radius of the approximate circle when the area of the spherical structure was calculated as a circle area was measured at 5 points, and the average value thereof was taken as the average size.

The measurement results are shown in Table 8.

[Comparative example 2]

For comparison, a coated tool was fabricated using the following fabrication method.

Using the above-mentioned tool substrates D, E, d, and e, stirring was continued for 12 hours under the state of maintaining the temperature of the thermostat shown in Table 7 different from that of Example 2, and then aged for 24 hours. Through such treatment, alumina sol was used to An aluminum oxide layer was formed until the predetermined target layer thickness shown in Table 8 was reached, and then the coated tool 10~ 18 (referred to as Comparative Example Tools 10~18).

For tools 10 to 18 of comparative examples, the results of observing the aluminum oxide layer with a scanning electron microscope (SEM) and a transmission electron microscope (TEM) confirmed that spherical structures were not dispersed in the film.

Next, a high-speed heavy-duty cutting test of cast iron was performed on the tools 13 to 24 of the present invention and the tools 10 to 18 of comparative examples described above under the following conditions.

The wear state of each tool was observed after the high-speed high-feed cutting test of cast iron under the following conditions (the usual cutting speed and feed rate were 250m/min and 0.3mm/rev.), and the back tool was measured surface wear.

Workpiece: JIS·FC350 round bar

Cutting speed: 400/min

Cutting depth: 1.5mm

Feed rate: 0.4mm/rev.

Cutting time: 20 minutes

These results are shown in Table 9.

Table 7

Table 8

Table 9

From the results shown in Tables 5 and 9, in the surface-coated cutting tools 1 to 24 of the present invention, the outermost surface of the tool base is coated with alumina by the sol-gel method, and the alumina layer has excellent properties. Excellent surface smoothness, lubricity, chip discharge, and welding resistance, so when it is used in high-speed heavy cutting of cast iron, carbon steel, etc., it will not cause abnormal damage such as chipping and peeling, and it will last for a long time Use to exhibit excellent wear resistance.

On the other hand, it is clear that the surface-coated cutting tools 1 to 18 of Comparative Examples, which do not contain a spherical structure on the outermost alumina layer but only consist of a matrix structure, cannot withstand high loads of heavy cutting. Abnormal damage in the blade face produces sharper crater wear, so wear resistance is poor and service life is reached in a short time.

In addition, in the above-mentioned examples, although the performance of the hard coating layer was evaluated using an insert-shaped tool, it goes without saying that similar results can also be obtained using a drill or an end mill.

Industrial availability

According to the surface-coated cutting tool of the present invention, alumina is coated on the outermost surface by the sol-gel method, and the alumina layer has excellent surface smoothness, lubricity, chip discharge, and welding resistance. When it is used in high-speed heavy cutting of cast iron, carbon steel, etc., it will not cause abnormal damage such as chipping and peeling. It will exhibit excellent wear resistance after long-term use, and can achieve long tool life. Big.

Claims (5)

1. A surface-coated cutting tool, which forms a hard coating on the surface of a tool substrate made of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet, is characterized in that, (a) having an aluminum oxide layer having an average layer thickness of 0.2 to 5 μm as a surface layer of the hard coating layer, (b) the above aluminum oxide layer consists of a matrix and spherical structures dispersed in the matrix, (c) The above-mentioned matrix is composed of an alumina crystal phase and an amorphous phase, and the above-mentioned globular structure is composed of one or both of the needle-like crystal phase and the plate-like crystal phase and an aggregate of the amorphous phase. 2. The surface-coated cutting tool according to claim 1, wherein: The area ratio of the spherical structure in the longitudinal section of the alumina layer is 20 to 60 area%. 3. The surface-coated cutting tool of claim 2, wherein: The approximate circle of the spherical structure has a radius of 0.02 to 0.5 μm. 4. The surface-coated cutting tool according to any one of claims 1 to 3, which is formed by coating the surface of the tool substrate made of tungsten carbide-based cemented carbide to form a hard coating layer, characterized in that , A base surface hardened layer having an average layer thickness of 0.5 to 3.0 μm is formed from the surface of the tool base in the depth direction, and the average content of Co as a binder phase metal contained in the base surface hardened layer is less than 2.0% by mass. 5. The surface-coated cutting tool according to any one of claims 1 to 3, which is formed by coating the surface of a tool substrate made of titanium carbonitride-based cermets to form a hard coating layer, wherein is that A base surface hardened layer having an average layer thickness of 0.5 to 3.0 μm is formed from the surface of the above-mentioned tool base toward the depth direction, and the total average content of Co and Ni as a binder phase metal contained in the base surface hardened layer is less than 2.0 mass %.