JP2005186221A - Surface coated cutting tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a long service life cutting tool, heightening the adhesiveness of a hard coating layer without the occurrence of peel-off between a TiCN layer and Al<SB>2</SB>O<SB>3</SB>layer under severe cutting conditions in which strong impact is applied to a cutting blade of a tool for intermittent cutting or the like, and having excellent breakage resistance and wear resistance. <P>SOLUTION: This surface coated cutting tool 1 has at least a charcoal titanium nitride layer 4 and a hard coated layer 3 including an aluminum oxide layer 6 as an upper layer on the surface of a base body 2. In observing an abrasion mark 7 of Calotest(R) for the hard coated layer 3 is worn away in a ball curved surface to expose the base body 2 around the abrasion mark 7 in which the surface coated cutting tool 1 is locally worn away so that the hard ball 13 turns on its axis while rolling, with hard balls 13 brought into contact with the surface of the surface coated cutting tool 1, the charcoal titanium nitride layer 4 observed in the periphery of the exposed base body 2 existing in the center of the abrasion mark 7 is composed of a lower texture 11 having zero or smaller crack width and an upper texture 12 observed in the periphery of the lower texture 11 and having larger crack width than the lower texture 11. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a surface-coated cutting tool having a hard coating layer formed on the surface thereof, and particularly has excellent chipping resistance and chipping resistance even in cutting where a large impact is applied to the cutting blade, such as intermittent cutting of cast iron. The present invention relates to a surface-coated cutting tool.

Conventionally, cutting tools widely used for metal cutting are titanium carbide (TiC) layer, titanium nitride (TiN) layer, titanium carbonitride (TiCN) on the surface of a substrate such as cemented carbide, cermet, and ceramics. ) And a surface-coated cutting tool in which a plurality of hard coating layers such as an aluminum oxide (Al ₂ O ₃ ) layer are formed.

  In such surface-coated cutting tools, in accordance with recent high-efficiency cutting, heavy impacts such as heavy interrupted cutting of metals are used under severe cutting conditions where the cutting blade is applied. In conventional tools, The hard coating layer cannot withstand the large impacts that occur suddenly, and the base is exposed due to chipping or peeling of the hard coating layer, which triggers a large chipping or abnormal wear on the cutting edge. There was a problem that the life could not be extended.

Therefore, Patent Document 1 can suppress delamination by providing a titanium carbonitride layer made of streaked titanium carbonitride crystal (vertically grown titanium carbonitride crystal) and dividing the layer with a granular titanium nitride layer. Is described to improve the fracture resistance of the tool.
Japanese Patent No. 3230372

  However, even with the structure of the titanium carbonitride layer described in Patent Document 1, abnormal wear due to chipping of the cutting edge, sudden defects, etc. still occur in cutting that suddenly receives a large impact such as heavy interrupted cutting. However, the tool life was shortened.

  In addition, even if the crystal width of the titanium carbonitride layer is simply reduced or increased, either the substrate wear resistance or chipping resistance deteriorates, and abnormal wear due to sudden chipping or chipping occurs. Or the problem of easy progress of wear, the optimization of the entire hard coating layer was not successful, and the tool life was limited.

  Therefore, the present invention has been made to solve the above-mentioned problems, and its purpose is to generate chipping and chipping even under severe cutting conditions such as intermittent cutting that suddenly applies a strong impact to the tool cutting edge. Accordingly, an object of the present invention is to provide a long-life cutting tool that has excellent chipping resistance and chipping resistance, and also has excellent wear resistance.

  As a result of studying the above problems, the present inventor observed so-called calotest wear marks on a surface-coated cutting tool having a hard coating layer including at least a titanium carbonitride layer on the surface of the substrate and an aluminum oxide layer thereon. It has been found that the distribution of partial wear resistance and fracture resistance of the hard coating layer can be evaluated. Then, when the wear scar is observed, the titanium carbonitride layer observed around the exposed substrate existing at the center of the wear scar has a substructure with a zero or small crack width, and around the substructure. The presence of an upper structure that is observed and has a crack width larger than that of the lower structure releases residual stress generated between the titanium carbonitride layer and the upper aluminum oxide layer by generating cracks in the upper structure. Thus, even when a sudden large impact is applied to the hard coating layer during interrupted cutting, a new large crack can be generated and the hard coating layer can be absorbed without chipping or chipping. At the same time, the presence of the lower structure of the titanium carbonitride layer that is less likely to generate cracks inhibits the progress of cracks generated in the upper structure. Of total titanium layer or hard coating layer without chipping or peeling, along with consequently possible to prevent chipping and peeling of the entire hard coating layer, wear resistance of the overall hard coating layer has invented improved.

  That is, the surface-coated cutting tool of the present invention is a surface-coated cutting tool having a hard coating layer including at least a titanium carbonitride layer and an aluminum oxide layer as an upper layer on the surface of the substrate. The hard sphere contact portion of the surface-coated cutting tool is locally worn so that the hard sphere rotates while rolling while the sphere is in contact with the hard coating layer so that the base is exposed at the center. When a calotest is performed to form a spherically curved wear mark and the wear mark is observed, the titanium carbonitride layer observed at the outer peripheral position of the exposed substrate present at the center of the wear mark has a crack width of zero or A small substructure and an upper structure observed at the outer peripheral position of the substructure and having a crack width larger than that of the substructure are present.

  Further, in the observation of the wear marks of the Calotest, the width of the crack observed in the lower structure of the titanium carbonitride layer should be 1/2 or less than the width of the crack observed in the upper structure. As a result, the adhesion between the titanium carbonitride layer and the aluminum oxide layer can be improved, and the progress of cracks in the titanium carbonitride layer itself can be suppressed. As a result, the chipping resistance and chipping resistance of the entire hard coating layer can be reduced. It is desirable to improve and maintain wear resistance.

  Here, the titanium titanium carbonitride layer is observed around the exposed substrate existing at the center of the wear scar, and is observed around the lower titanium carbonitride layer having a crack width of zero or small and the lower titanium carbonitride layer. The presence of multiple layers with the upper titanium carbonitride layer having a crack width larger than that of the lower titanium carbonitride layer means that cracks generated at the upper part of the titanium carbonitride layer progress without stopping and reach the lower part. This is desirable because chipping and chipping can be surely suppressed.

Further, the film thickness t ₁ of the lower titanium carbonitride layer is 1 μm ≦ t ₁ ≦ 10 μm, the film thickness t ₂ of the upper titanium carbonitride layer is 0.5 μm ≦ t ₂ ≦ 5 μm, and 1 <t ₁ / Satisfying the relationship of t ₂ ≦ 5 can improve the adhesion between the titanium carbonitride layer and the aluminum oxide layer, and can suppress the development of cracks in the titanium carbonitride layer itself, and the entire hard coating layer This is desirable because the impact resistance of the tool can be improved, chipping and chipping as a whole tool can be prevented, and high wear resistance can be maintained.

  Further, the titanium carbonitride layer is composed of titanium carbonitride particles having a streak structure extending perpendicularly to the substrate surface, and the average crystal width of the titanium carbonitride particles forming the upper titanium carbonitride layer is the lower carbonitride Being larger than the average crystal width of the titanium carbonitride particles forming the titanium layer can suppress the cracks generated in the upper titanium carbonitride layer from progressing to the lower titanium carbonitride layer, and also include an aluminum oxide layer and a titanium carbonitride layer. It is possible to control the adhesive force between the two by reducing the residual stress of the material and minimizing the occurrence of cracks. This is desirable because the wear resistance and delamination resistance of the hard coating layer can be improved and the wear resistance and fracture resistance of the entire tool can be brought into an optimum state.

In this case, the average crystal width w ₂ in the upper layer in the titanium carbonitride layer is 0.2 to 1.5 μm, and the average crystal width w ₁ in the lower titanium carbonitride layer is When the average crystal width w ₂ of the upper titanium carbonitride layer is 0.7 times or less, the fracture resistance and chipping resistance of the titanium carbonitride crystal itself can be improved, and the adhesion with the aluminum oxide layer can be increased. It is desirable to control and increase the wear resistance and fracture resistance of the hard coating layer as a whole.

Further, when the titanium carbonitride layer was expressed as _{Ti (C 1-x N x} ), x in the lower titanium carbonitride layer is 0.55 to .80, x in the upper titanium carbonitride layer is 0. Containing 40 to 0.55 suppresses the crack generated in the base upper titanium carbonitride layer from progressing to the lower titanium carbonitride layer, and increases the chipping resistance and chipping resistance of the hard coating layer, It is desirable because high wear resistance can be maintained.

  Further, since the adhesion force in the scratch test of the aluminum oxide layer is 10 to 50 N, it is possible to suppress the peeling of the hard coating layer in continuous cutting and to have high wear resistance, and in the intermittent cutting, the aluminum oxide layer is appropriate. This is desirable because it is possible to increase the chipping resistance and chipping resistance by suppressing the peeling of the hard layer that reaches the substrate.

  Here, in the observation of wear marks in the Calotest, cracks are observed from the interface between the aluminum oxide layer and the titanium carbonitride layer to the inside of the aluminum oxide layer, indicating that the interface between the titanium carbonitride layer and the aluminum oxide layer It is desirable in that it can effectively eliminate the residual stress generated in the film, and can prevent the occurrence of excessive cracks in the titanium carbonitride layer, thereby preventing chipping and peeling of the titanium carbonitride layer.

  The surface-coated cutting tool of the present invention is a surface-coated cutting tool having a hard coating layer including at least a titanium carbonitride layer on the surface of a substrate and an aluminum oxide layer on the surface. It is possible to evaluate the distribution of partial wear resistance and fracture resistance of the layer, and by observing the wear scar, the titanium carbonitride layer observed around the exposed substrate existing in the center of the wear scar However, the presence of a substructure whose crack width is zero or small and an upper structure which is observed around the lower structure and has a crack width larger than that of the lower structure, thereby generating a crack in the upper structure, thereby carbonitriding. Residual stress generated between the titanium layer and the upper aluminum oxide layer is released, and the base, especially gray cast iron (FC material) and ductile cast iron (FCD) ) Severe cutting conditions such as heavy interrupted cutting of metal such as cast iron in which high-hardness graphite particles are dispersed, such as severe cutting conditions that apply a strong impact to the cutting edge, continuous cutting conditions, and these intermittent and continuous cutting Under the combined cutting conditions, even if a sudden large impact is applied to the hard coating layer, a new large crack is generated and the hard coating layer is absorbed without chipping or chipping. As a result, the presence of the lower structure of the titanium carbonitride layer in which cracks are difficult to generate prevents the progress of cracks generated in the upper structure, so that the titanium carbonitride layer does not chip or peel off. In addition to preventing chipping and peeling of the entire hard coating layer, it has excellent chipping and chipping resistance that maintains the wear resistance of the entire hard coating layer. Cutting tools that can be obtained.

  FIG. 1 (a is an example of the present invention, (b) is a comparative example) of an example of a surface-coated cutting tool of the present invention and a metallographic image of a wear mark of Calotest, a scanning surface of a fractured surface including a hard coating layer Description will be made based on FIG. 2 which is an electron microscope (SEM) photograph.

  According to FIGS. 1 and 2, a surface-coated cutting tool (hereinafter simply abbreviated as a tool) 1 includes tungsten carbide (WC) and, if desired, carbides, nitrides of Group 4a, 5a, and 6a metals in the periodic table. A cemented carbide obtained by bonding a hard phase composed of at least one selected from the group of carbonitrides with a binder phase composed of an iron group metal such as cobalt (Co) and / or nickel (Ni), a Ti-based cermet, Alternatively, the hard coating layer 3 is formed by chemical vapor deposition (CVD) on the surface of the substrate 2 made of ceramics such as silicon nitride, aluminum oxide, diamond, cubic boron nitride or the like.

  According to this embodiment, as shown in FIG. 2, the hard coating layer 3 has at least a titanium carbonitride (TiCN) layer 4 and an aluminum oxide layer 6 as an upper layer thereof. Further, FIG. 1 shows the wear scar 7 of the Calotest observed with a metal microscope or a scanning electron microscope, for example, at a magnification of 4 to 50 times (5 times in FIG. 1).

  In addition, as shown in FIG. 3, the calotest defined as the evaluation item of the present invention is a state in which a hard sphere 13 made of metal or cemented carbide is brought into contact with the surface of the tool 1, that is, the surface of the hard coating layer 3. The tool 1 is locally worn by rotating the support rod 14 supporting the hard sphere 13 and rotating the hard sphere 13 while rolling, and the base 2 is exposed at the center of the wear mark 7 as shown in FIG. In this way, the hard coating layer 3 is worn on a spherical curved surface, and generally the film thickness of each layer is estimated by observing the width of each layer of the hard coating layer 3 observed in the wear scar 7. Is the method.

  According to the present invention, in the observation of the wear scar 7 of the Calotest as shown in FIG. 1, the titanium carbonitride layer 4 observed at the outer peripheral position of the exposed substrate existing at the center of the wear scar 7 as shown in FIG. A major feature is that the lower structure 11 having a zero or small crack width and the upper structure 12 observed at the outer peripheral position of the lower structure 11 and having a crack width larger than that of the lower structure 11 exist.

  With the above configuration, the residual stress due to the difference in thermal expansion coefficient between the aluminum oxide layer 6 and the titanium carbonitride layer 4 is generated in the upper structure 12 on the surface side of the titanium carbonitride layer 4 during cooling after coating. Thus, even when a sudden large impact is applied to the hard coating layer 3, a new large crack is generated and the hard coating layer is not chipped or broken. The presence of the lower structure 11 of the titanium carbonitride layer 4 that can absorb and hardly generate the crack 5 prevents the progress of the crack 5 generated in the upper structure 12, so that the titanium carbonitride layer 4 is chipped or As a result, the chipping and peeling of the entire hard coating layer 3 can be prevented without peeling, and the wear resistance of the entire hard coating layer 3 is improved. Gray cast iron (FC material) and ductile iron tool 1 having the heavy intermittent excellent chipping resistance and chipping resistance even in the cutting of cast iron such as high hardness graphite particles are dispersed like (FCD material) is obtained.

  That is, in the observation of the wear scar 7, if there is no crack 5 in the upper structure 12 of the TiCN layer 4, the residual stress between the titanium carbonitride layer 4 and the aluminum oxide layer 6 is not released, and the hard coating layer 3 has a large impact. Is added, a large crack 5 develops in one or both of the titanium carbonitride layer 4 and the aluminum oxide layer 6, and the hard coating layer is likely to be chipped or chipped. Moreover, when the generation ratio of the crack 5 is the same in the entire titanium carbonitride layer 4 as shown in FIG. 1B, the crack 5 is generated when the crack 5 due to the residual stress with the aluminum oxide layer 6 is generated. It progresses to the entire titanium carbonitride layer 4, and in this case also, the hard coating layer 3 is likely to be chipped or chipped.

  According to the present invention, the wear mark 7 of the calotest is a state in which the hard coating layer 3 is worn on the spherical curved surface so that the base 2 is exposed at the center of the wear mark 7. It was found that the properties and characteristics of the hard coating layer 3 can be evaluated by observing the wear, delamination, and the progress of cracks 5 of each layer of the hard coating layer 3 included in 7 for each layer.

  Here, since the crack 5 in the titanium carbonitride layer 4 may not be observed accurately if the size of the exposed substrate 2 is too large or too small, the substrate exposed in the wear scar 7. It is preferable to adjust the wear conditions (time, type of hard sphere, abrasive, etc.) of the calotest so that the diameter of 2 is 0.1 to 0.6 times the diameter of the entire wear scar 7.

Further, as described in a drawing-substitute scanning electron micrograph (SEM) for explaining the structure of the hard coating layer 3 in FIG. 2, the crack width w observed in the lower structure 11 of the titanium carbonitride layer 4. ₁ is 1/2 or less, particularly 1/3 or less in terms of the ratio (b ₁ / b ₂ ) to the crack width b ₂ observed in the upper structure 12, the titanium carbonitride layer 4 and the aluminum oxide layer 6. In addition to improving the adhesion to the titanium carbonitride layer 4, it is also possible to suppress the development of cracks 5 in the titanium carbonitride layer 4 itself, improving the chipping resistance and fracture resistance of the hard coating layer 3 as a whole, and wear resistance. Is desirable to maintain.

  Further, according to FIG. 3, which is an enlarged view of the main part of FIG. 1, 2 or FIG. 1, the titanium carbonitride layer 4 is observed at the outer peripheral position of the exposed base 2 existing at the center of the wear scar 7 and crack width And a lower titanium carbonitride layer (hereinafter simply referred to as a lower layer) 15 and an upper titanium carbonitride layer (hereinafter simply referred to as an upper layer) that is observed around the lower layer 15 and has a crack width larger than that of the lower layer 15. (This is abbreviated as a layer.) With this structure, the crack 5 generated in the upper part of the titanium carbonitride layer 4 does not progress and reach the lower part. In addition, chipping and chipping of the hard coating layer 3 can be prevented.

Further, the thickness t ₂ of the upper layer 16 is 0.5 μm ≦ t ₂ ≦ 5 μm, the thickness t ₁ of the lower layer 15 is 1 μm ≦ t ₁ ≦ 10 μm, and 1 <t ₁ / t ₂ ≦ 5. Satisfying the condition can improve the adhesion between the titanium carbonitride layer 4 and the aluminum oxide layer 6 and can suppress the development of the crack 5 of the titanium carbonitride layer 4 itself, and the impact resistance of the hard coating layer 3 as a whole. This is desirable because it can prevent chipping and chipping of the tool 1 as a whole and maintain high wear resistance.

As shown in FIG. 4, the titanium carbonitride layer 4 is composed of titanium carbonitride particles having a streak structure extending perpendicularly to the surface of the substrate 2, and the upper layer 16 is an average crystal width w _{1 of the} titanium carbonitride particles. The lower layer 15 is formed of a streak structure in which the average crystal width w ₂ of the titanium carbonitride particles is small, so that the crack 5 generated in the upper layer 16 is prevented from progressing to the lower layer 15. In addition, the residual stress between the aluminum oxide layer 6 and the titanium carbonitride layer 4 can be reduced to minimize the occurrence of cracks and control the adhesion between them. This is desirable because the wear resistance and delamination resistance of the hard coating layer 3 can be improved, and the wear resistance and fracture resistance of the tool 1 as a whole can be brought into an optimum state.

  Here, the titanium carbonitride particles having a streak structure extending perpendicularly to the surface of the substrate 2 are crystals having a crystal length in the direction perpendicular to the interface with the substrate 2 / average crystal width = aspect ratio of 2 or more. Refers to an organization. Moreover, in the cross-sectional structure | tissue observation of the hard coating layer 3 as shown in FIG. 2, the mixed crystal which the granular titanium carbonitride crystal mixed in the ratio of 30 area% or less may be sufficient.

In this case, the average crystal width w ₂ in the upper layer 16 in the titanium carbonitride layer 4 is 0.2 to 1.5 μm, particularly 0.2 to 0.5 μm, and the average in the lower layer 15 is When the crystal width w ₁ is 0.7 times or less of the average crystal width w ₂ of the upper layer 16, the fracture resistance and chipping resistance of the titanium carbonitride layer 4 itself can be improved, and the aluminum oxide layer 6 It is desirable to control the adhesion force between the hard coating layer 3 and the wear resistance and fracture resistance of the hard coating layer 3 as a whole.

  Further, in the present invention, as a method for measuring the average crystal width of the titanium carbonitride particles comprising streak-like crystals, the cross section including the hard coating layer 3 is observed with a scanning electron micrograph, A straight line parallel to the interface between the substrate 2 and the hard coating layer 3 is drawn in the thickness region (see line segments A and B in FIG. 4), and the average value of the width of each particle on the line segment, that is, the line segment length Is divided by the number of grain boundaries crossing the line segment to be the average crystal width w.

Further, when the titanium carbonitride layer 4 is expressed as Ti (C _1-x N _x ), x is 0.55 to 0.80 in the lower layer 15, and x is 0.40 to 0.55 in the upper layer 16. The composition is desirable in order to suppress the crack generated in the upper layer 16 from progressing to the lower layer 15 and to improve the chipping resistance and fracture resistance of the hard coating layer 3.

  Furthermore, since the adhesion force in the scratch test of the aluminum oxide layer 6 is 10 to 50 N, peeling of the hard coating layer 3 can be suppressed in continuous cutting and the wear resistance is improved. In the intermittent cutting, the aluminum oxide layer 6 is By causing moderate peeling, it is possible to suppress the peeling of the hard layer 3 that reaches the substrate 2, which is desirable because the chipping resistance and chipping resistance are improved.

  Here, in the observation of wear marks in the calotest, it is observed that cracks are observed from the interface between the aluminum oxide layer 6 and the titanium carbonitride layer 4 to the inside of the aluminum oxide layer 6, that is, the titanium carbonitride layer 4 and the aluminum oxide layer 6. This is desirable in that it can effectively eliminate the residual stress generated at the interface with the carbon black and prevent excessive cracks from occurring in the titanium carbonitride layer 4 to prevent chipping and peeling of the titanium carbonitride layer 4.

  Titanium nitride (between the substrate 2 and the titanium carbonitride layer 4, between the titanium carbonitride layer 4 and the aluminum oxide layer 6, between the titanium carbonitride layer formed in multiple layers, and above the aluminum oxide layer) At least one layer selected from the group consisting of a TiN) layer, a titanium carbide (TiC) layer, a titanium carbonitride oxide (TiCNO) layer, a titanium carbonate (TiCO) layer, and a titanium nitride oxide (TiNO) layer, and the lowermost layer 18 is particularly nitrided By interposing the titanium layer, the diffusion of the components of the substrate 2 is improved, the adhesion between the hard coating layers 3 is improved, the structure of the titanium carbonitride layer 4 and the aluminum oxide layer 6, the crystal structure, the adhesion and cracking. It is possible to control the occurrence state.

  In addition, the aluminum oxide layer 6 formed as the upper layer of the titanium carbonitride layer 4 has an adhesive force of 10 to 50 N, particularly 10 to 30 N as measured by an adhesive force measured in a scratch test. Excellent abrasion resistance can be exhibited without occurrence of film peeling, and only the aluminum oxide layer 6 peels during intermittent cutting, and the tough titanium carbonitride layer 4 remains without peeling and wear. This is desirable because it can suppress rapid progress and can exhibit excellent fracture resistance.

  The scratch test refers to scratching the stylus while rubbing the sample surface at a constant speed while applying a constant load while the stylus is in contact with the sample surface, and the hard coating layer of the sample is peeled off. This is a test method for measuring the adhesion of each layer in the hard coating layer by reading the load value as the adhesion of the peeled layer.

  Here, the aluminum oxide layer 6 used in the present invention desirably has an α-type crystal structure. Conventionally, an aluminum oxide crystal having an α-type crystal structure has excellent wear resistance, but the particle size at the interface between the aluminum oxide layer 6 and the titanium carbonitride layer 4 is large because the particle size of the aluminum oxide crystal produced by nucleation is large. The contact area between them becomes small and the adhesive force becomes weak, so that the aluminum oxide layer 6 is easily peeled off. However, according to the above configuration, even if the aluminum oxide crystal in the aluminum oxide layer 6 has an α-type crystal structure, the adhesive force of the aluminum oxide layer 6 can be easily controlled in the range of 10 to 50 N, and the tool life can be improved. A long tool 1 can be obtained.

When the Al ₂ O ₃ layer 6 has an α-type crystal structure, a titanium carbonate layer, a titanium oxynitride layer, or a carbonitridation layer of 0.2 μm or less between the titanium carbonitride layer 4 and the aluminum oxide layer 6 is used. By interposing the intermediate layer 8 made of any of the titanium layers, the α-type crystal structure can be stably grown. Further, the thickness of the aluminum oxide layer 6 is 3 to 8 μm, and while maintaining wear resistance, particularly wear resistance and welding resistance to cast iron, film peeling can be prevented and chipping resistance can be improved. Desirable in terms.

  In addition, it is desirable to coat the lowermost layer 18 made of a titanium nitride (TiN) layer between the titanium carbonitride layer 4 and the substrate 2 in order to improve adhesion and prevent a decrease in wear resistance due to diffusion of components of the substrate 2. . In addition, it is desirable that the layer thickness of the lowermost layer 18 is in a range of 0.1 to 2 μm from the viewpoint of preventing a decrease in adhesive force.

  In addition, by forming a titanium nitride layer as the outermost surface layer 19 of the hard coating layer 3, the tool 1 exhibits a gold color, so that it is easy to determine whether the tool 1 has been discolored and used, It is desirable because the progress of wear can be easily confirmed.

(Production method)
In order to manufacture the above-mentioned surface-coated cutting tool, first, an inorganic powder such as a metal carbide, nitride, carbonitride, oxide, etc. that can form the above-mentioned hard alloy by firing, metal powder, carbon powder, etc. Are added and mixed as appropriate, and then molded into a predetermined tool shape by a known molding method such as press molding, cast molding, extrusion molding, or cold isostatic pressing, and then fired in a vacuum or non-oxidizing atmosphere. By doing so, the base body 2 made of the hard alloy described above is produced.

Next, after polishing the surface of the base 2 as desired, the hard coating layer 3 is formed on the surface by, for example, chemical vapor deposition (CVD). The film formation conditions of the streaky titanium carbonitride layer 4 are, for example, 0.1% to 10% by volume of titanium chloride (TiCl ₄ ) gas and 0% to 60% of nitrogen (N ₂ ) gas as a reaction gas composition. %, Methane (CH ₄ ) gas is 0 to 0.1% by volume, acetonitrile (CH ₃ CN) gas is 0.1 to 3% by volume, and the balance is hydrogen (H ₂ ) gas to adjust the reaction It introduce | transduces in a chamber and forms into a film at 800-1100 degreeC and 5-85 kPa inside the chamber.

Here, in the present embodiment, the film formation late stage of the titanium carbonitride layer (upper layer 12) is higher than the proportion of CH ₃ CN in the reaction gas used in the film formation early period of the titanium carbonitride layer (film formation of the lower layer 11). The particle diameter of the titanium carbonitride particles in the upper layer 12 is made larger than that in the lower layer 11 by increasing the mixing ratio of acetonitrile (CH ₃ CN) gas in the reaction gas used for the film formation.

  Specifically, it is controlled by setting the ratio of acetonitrile gas introduced at the latter stage of the formation of the titanium carbonitride layer to 1.5 times or more with respect to the introduction ratio of acetonitrile gas used at the first stage of the formation of the titanium carbonitride layer. Is possible.

  Here, if the ratio of acetonitrile gas in the reaction gas is less than 0.1% by volume among the above film forming conditions, it cannot be grown into a streaky titanium carbonitride crystal and becomes a granular crystal. Conversely, if the mixing ratio of acetonitrile gas in the reaction gas exceeds 3% by volume, the average crystal width of the titanium carbonitride crystal becomes large, and the ratio cannot be controlled.

  Note that the average crystal width of the titanium carbonitride crystal can be controlled to a predetermined configuration by a method in which the film formation temperature is increased in the later stage of film formation rather than in the earlier stage of film formation instead of changing the amount of acetonitrile gas introduced into the reaction gas. Is possible.

And according to this invention, the aluminum oxide layer 6 is formed into a film continuously. As a method of forming the aluminum oxide layer 6, ₃ to 20% by volume of aluminum chloride (AlCl ₃ ) gas, 0.5 to 3.5% by volume of hydrogen chloride (HCl) gas, and carbon dioxide (CO ₂ ) gas are used. Using a mixed gas composed of 0.01 to 5.0% by volume, 0 to 0.01% by volume of hydrogen sulfide (H ₂ S) gas, and the remainder consisting of hydrogen (H ₂ ) gas, 900 to 1100 ° C. and 5 to 10 kPa Is desirable.

Further, in order to form a titanium nitride (TiN) layer, the reaction gas composition is 0.1 to 10% by volume of titanium chloride (TiCl ₄ ) gas, 0 to 60% by volume of nitrogen (N ₂ ) gas, and the rest A mixed gas composed of hydrogen (H ₂ ) gas is sequentially adjusted and introduced into the reaction chamber, and the inside of the chamber may be set to 800 to 1100 ° C. and 5 to 85 kPa.

Further, titanium carbonitride (for forming a TiCNO layer, titanium chloride (TiCl ₄ ) gas is 0.1 to 3% by volume, methane (CH ₄ ) gas is 0.1 to 10% by volume, carbon dioxide (CO ₂ )
A mixed gas consisting of 0.01 to 5% by volume of gas, 0 to 60% by volume of nitrogen (N ₂ ) gas, and the remainder of hydrogen (H ₂ ) gas is sequentially adjusted and introduced into the reaction chamber. What is necessary is just to set it as 800-1100 degreeC and 5-85 kPa.

  At this time, in addition to the above-described method, after the hard coating layer is formed by the chemical vapor deposition method, the cooling rate of the chamber up to 700 ° C. is controlled to 12 to 30 ° C./min. A structure | tissue can be controlled to the structure | tissue by which a predetermined crack is observed by the said Calotest.

  The present invention is not limited to the above embodiment. For example, in the above description, the case where the chemical vapor deposition (CVD) method is used as the film forming method has been described. It may be formed by a physical vapor deposition (PVD) method.

  6% by mass of metallic cobalt (Co) powder with an average particle size of 1.2 μm and 0% of titanium carbide (TiC) powder with an average particle size of 2.0 μm with respect to tungsten carbide (WC) powder with an average particle size of 1.5 μm. .5% by mass, TaC powder was added and mixed at a rate of 5% by mass, formed into a cutting tool shape (CNMA120204) by press molding, and then subjected to binder removal treatment at 1500 ° C. in a vacuum of 0.01 Pa. A cemented carbide was prepared by firing for 1 hour. Further, the prepared cemented carbide was subjected to blade edge processing (Honing R) by brushing.

And for the above cemented carbide, sample No. 1 was formed by forming a hard coating layer composed of a multilayer film having the structure shown in Table 2 under the conditions shown in Table 1 on the various hard coating layers by the CVD method. 1 to 8 surface-coated cutting tools were produced.

About the obtained tool, the scanning electron microscope (SEM) photograph was taken about the arbitrary fractured surfaces including the cross section of a hard coating layer, or 5 places of grinding | polishing surfaces, and the structure | tissue of the TiCN layer was observed in each photograph. At this time, the height of the total thickness of the titanium carbonitride layer is 1/5 of the total thickness from the substrate side and the height of 1/5 of the total thickness from the aluminum oxide layer (surface) side, respectively. The line A and the line B as shown in FIG. 2 are drawn, the number of grain boundaries crossing each line segment is measured, and the value converted into the crystal width of the titanium carbonitride crystal is calculated. The average value of the obtained crystal widths was calculated as the average crystal width (w ₁ , w ₂ ).

Whether the titanium carbonitride layer is a single layer or a multilayer is confirmed by the above metal micrograph or SEM photograph. If the titanium carbonitride layer is a multilayer, the film thicknesses t ₂ and t ₁ of the upper layer and the lower layer are measured, and the relational expression The value of t ₁ / t ₂ was calculated. Note that when the layer boundaries in the observation of the titanium carbonitride layer is not clear, the mirror surface by polishing the fracture surface, further alkaline potassium ferricyanide solution (Murakami () Reagent:? 10% KOH + 10% K 3 Fe The etching treatment according to (CN) ₆ ) was performed, and this was observed with a metallographic microscope or SEM. The results are shown in Table 2.

In addition, the crack state of the hard coating layer of the surface-coated cutting tool was observed with a metal microscope or SEM for the wear scar generated by the calotest test performed under the following conditions, and the titanium carbonitride layer observed with the calotest wear scar was observed. The widths b ₁ and b ₂ of the cracks in the lower structure and the upper structure were measured, respectively. The results are shown in Table 2.

Equipment: CSEM-CALOTEST manufactured by Nanotech
Steel balls 30 mm diameter spherical steel balls Diamond paste 1/4 MICRON
Cracks in a worn state so that the diameter of the substrate exposed in the wear scar is 0.1 to 0.6 times the diameter of the entire wear scar (0.3 to 0.7 mm in this measurement) Was observed. Incidentally, the width of the cracks, the average value = b _1, titanium carbonitride of wear scar 7 crack width at the position of 1/5 length from the substrate (in) side of the titanium carbonitride layer region of the wear track aluminum oxide layer of the layer region was calculated as the average value = b ₂ crack width at the position of the (outer) side 1/5 length. The results are shown in Table 2.

  Furthermore, the adhesive force of the hard coating layer was measured by a scratch test under the following conditions. The results are shown in Table 2.

Apparatus: CSEM-REVETEST manufactured by Nanotech
Measurement conditions Table speed: 0.17 mm / sec
Load speed 100N / min
Indenter Conical diamond indenter (Diamond contactor manufactured by Tokyo Diamond Tool Mfg. Co., Ltd .: N2-1487)
Curvature radius: 0.2mm
Ridge angle: 120 °

In Table 2, the sample No. 5 consists of a titanium carbonitride layer having a gradient structure prepared by continuously increasing the conditions of the titanium carbonitride layer 6 (TiCN6) in Table 1, that is, the ratio of acetonitrile (CH ₃ CN) gas in the mixed gas continuously. Is.

  Then, using this cutting tool, a continuous cutting test and an intermittent cutting test were performed under the following conditions to evaluate the wear resistance and fracture resistance.

(Continuous cutting test)
Work Material: Ductile Cast Iron Sleeve Material (FCD700)
Tool shape: CNMA120204
Cutting speed: 250 m / min Feed speed: 0.4 mm / rev
Cutting depth: 2mm
Cutting time: 20 minutes Others: Use of water-soluble cutting fluid Evaluation item: Observe the cutting edge with a microscope and measure the amount of flank wear and tip wear (intermittent test)
Work material: Ductile cast iron 4-slot sleeve material (FCD700)
Tool shape: CNMA120204
Cutting speed: 200 m / min Feeding speed: 0.3 to 0.5 mm / rev
Cutting depth: 2mm
Other: Use of water-soluble cutting fluid Evaluation item: Number of impacts leading to breakage
Observe the peeling state of the hard coating layer of the cutting edge with a microscope at the point of impact 1000 times

  From Tables 1 to 3, sample No. 1 consisting of a single layer of titanium carbonitride layer and having uniform cracks in the entire titanium carbonitride layer. In No. 8, chipping occurred in the hard coating layer of the cutting edge portion from the beginning of cutting, and the chipping occurred early due to this chipping.

  In addition, the sample No. 1 whose cooling rate from the film formation to 700 ° C. is slower than 10 ° C./min. No. 6 indicates that the occurrence of cracks was sample No. The distribution of cracks was uniform although it was smaller overall than 8. In the cutting, fine chipping occurred and the chip was lost after 1100 impacts.

  Furthermore, Sample No. 2 in which two titanium carbonitride layers were formed under the same film formation conditions. In No. 7, the crack width was uniform in the observation of the wear marks of the Calotest, and chipping occurred again and chipped when 2500 pieces were processed.

  On the other hand, according to the present invention, the upper structure (upper layer) crack width on the aluminum oxide layer side is larger than the crack width of the lower structure (lower layer) on the substrate side of the titanium carbonitride layer. No. In Nos. 1 to 5, peeling of the hard coating layer did not occur, it had a long life both in continuous cutting and intermittent cutting, and had excellent cutting performance in both chipping resistance and chipping resistance. In particular, Sample No. 2 having a multilayered titanium carbonitride layer. Samples 2 and 3 in which the crack width of the lower layer was difficult to be observed as 1 to 4 and the crack width of 0.5 μm or less were the most excellent in both wear resistance and fracture resistance.

It is a metal-microscope image ((a) example of this invention, (b) conventional example) of the abrasion trace which carried out the calotest of the surface coating cutting tool. It is a scanning electron microscope image about the hard coating layer area | region in the torn surface of the surface coating cutting tool of this invention. It is a schematic diagram for demonstrating the testing method of a caro test. It is a principal part enlarged photograph about the metal microscope image of the wear scar of FIG. It is the photograph which observed FIG. 4 with the scanning electron microscope (SEM).

Explanation of symbols

1: Surface coating cutting tool 2: Substrate 3: Hard coating layer 4: Titanium carbonitride layer 5: Crack 6: Aluminum oxide layer 7: Wear scar 8: Intermediate layer 11: Substructure 12 of titanium carbonitride layer: Titanium carbonitride Layer upper structure 13: Hard sphere 14: Support rod 15: Lower titanium carbonitride layer (lower layer)
16: Upper titanium carbonitride layer (upper layer)
18: Lowermost layer 19: Outermost surface layer b ₁ : Average crack width b ₂ in the lower structure (substrate side) of the titanium carbonitride layer Average crack width w ₁ in the upper structure (aluminum oxide layer side) of the titanium carbonitride layer: Average crystal width w ₂ on the substrate side of the titanium carbonitride layer: Average crystal width t ₁ on the Al ₂ O ₃ layer side of the titanium carbonitride layer: Film thickness t ₂ of the lower layer of the titanium carbonitride layer: of the titanium carbonitride layer Upper layer thickness

Claims (9)

In a surface-coated cutting tool having a hard coating layer including at least a titanium carbonitride layer on the surface of a substrate and an aluminum oxide layer as an upper layer thereof, the hard sphere is brought into contact with the surface of the surface-coated cutting tool. A carotest that locally wears the hard sphere contact portion of the surface-coated cutting tool so as to rotate while rolling, and forms a spherical curved wear mark on the hard coating layer so that the substrate is exposed at the center. And when the wear scar is observed, the titanium carbonitride layer observed at the outer peripheral position of the exposed substrate present at the center of the wear scar has a substructure with a zero or small crack width, and the outer peripheral position of the substructure. A surface-coated cutting tool characterized in that an upper structure having a crack width larger than that of the lower structure exists. In the observation of wear marks of the Calotest, the width of the crack observed in the lower structure of the titanium carbonitride layer is 1/2 or less than the width of the crack observed in the upper structure. The surface-coated cutting tool according to claim 1. The titanium carbonitride layer is observed around the exposed substrate existing at the center of the wear scar, and the lower titanium carbonitride layer having a crack width of zero or small and the lower titanium carbonitride layer is observed around the lower titanium carbonitride layer. The surface-coated cutting tool according to claim 1 or 2, comprising a plurality of layers including an upper titanium carbonitride layer having a crack width larger than that of the titanium carbonitride layer. The film thickness t ₁ of the lower titanium carbonitride layer is 1 μm ≦ t ₁ ≦ 10 μm, the film thickness t ₂ of the upper titanium carbonitride layer is 0.5 μm ≦ t ₂ ≦ 5 μm, and 1 <t ₁ / t ₂ The surface-coated cutting tool according to claim 3, wherein a relationship of ≦ 5 is satisfied. The titanium carbonitride layer is composed of titanium carbonitride particles having a streak structure extending perpendicularly to the substrate surface, and the average crystal width of the titanium carbonitride particles forming the upper titanium carbonitride layer is the lower titanium carbonitride layer 5. The surface-coated cutting tool according to claim 3, wherein the surface-coated cutting tool is larger than an average crystal width of titanium carbonitride particles forming the following. The average crystal width w ₂ in the upper layer in the titanium carbonitride layer is 0.2 to 1.5 μm, and the average crystal width w ₁ in the lower titanium carbonitride layer is the average of the upper titanium carbonitride layer. surface-coated cutting tool according to claim 5, wherein a is less than 0.7 times the crystal width w _2. When said titanium carbonitride layer was expressed as _{Ti (C 1-x N x} ), x in the lower titanium carbonitride layer is 0.55 to 0.80, x in the upper titanium carbonitride layer is 0.40 The surface-coated cutting tool according to any one of claims 3 to 6, which has a composition of 0.55. The surface-coated cutting tool according to any one of claims 1 to 7, wherein an adhesion force in the scratch test of the aluminum oxide layer is 10 to 50N. 9. The surface-coated cutting tool according to claim 8, wherein cracks are observed from an interface between the aluminum oxide layer and the titanium carbonitride layer in the wear trace of the calotest from the inside of the aluminum oxide layer.

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