JP2006026814A - Coated cutting tip - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated cutting tip with excellent deficit-proof property hardly occurring melting and solving a problem wherein the coated cutting tip is used under a severe cutting condition such as high speed, high feeding and high cutting-in accompanying with high efficiency of cutting work recently, hardly-cutting material of a workpiece is advanced and melting easily occurs when the cutting work or cutting work of the hardly-cutting material is performed under such a severe cutting condition. <P>SOLUTION: The coated cutting tip is constituted by a cutting tip base material comprising a hard material; and a coated layer having thickness of 3-30 μm coated on a surface. Arithmetic average roughness Ra relative to reference length 5 μm of a cutting blade ridge line part and the coated layer surface of a rake surface is 0.15 μm or less and width of a crack existing on the cutting blade ridgeline part and the coated layer of the rake surface is made to 0.10 μm or less. Thereby, enhancement of melting-resistance and deficit-proof can be realized. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a coated cutting tip in which a surface of a cutting tip base material made of a hard material is coated with a coating layer. In particular, the present invention relates to a coated cutting tip for cutting a work material that is likely to be welded during cutting, such as ductile cast iron or low carbon steel.

Coated cutting tips in which the surface of a cutting tip base material is coated with a coating layer are widely used. If the surface of the coated cutting tip is rough, welding is likely to occur. As a cutting tool insert whose surface is smoothed, there is a cutting tool insert whose coating is smoothed by blasting with alumina powder (see, for example, Patent Document 1). However, this cutting tool insert has a problem of low fracture resistance. In addition, since the blast treatment is performed with coarse alumina powder, there is a limit to improving the smoothness of the surface of the refractory layer. Moreover, since the coarse-grained medium is strongly projected, the outermost layer of the rake face and the cutting edge ridge line portion is removed. For this reason, the surface material of the rake face and the cutting edge ridge line portion is different from the surface material of the flank face, and the aesthetic appearance is impaired.

Japanese Patent Application Laid-Open No. 08-052603

Coated cutting tips in which the surface of a cutting tip base material is coated with a coating layer are widely used. In recent years, higher efficiency of cutting has been demanded, and severe cutting such as high speed, high feed and high cutting has been performed. In addition, work materials have become more difficult to cut as well as higher performance and lighter weight. If cutting is performed under such severe cutting conditions or cutting of difficult-to-cut materials, welding is likely to occur. Therefore, an object of the present invention is to provide a coated cutting tip that hardly causes welding and has excellent fracture resistance.

As a result of researches aimed at solving the above-mentioned problems, the present inventor performs wet blasting treatment using a fine hard ceramic powder on the cutting edge ridge line portion and rake face of the coated cutting tip where welding is likely to occur. Thus, it was found that the surface can be smoothed without expanding cracks present in the coating layer. According to the present invention, cracks existing in the coating layer are not spread, so that the chipping resistance is not lowered and the welding is reduced by smoothing the surface. It is possible to extend the tool life by suppressing the chipping.

  In the coating layer of the conventional coated cutting tip, there are cracks such as cooling cracks generated by cooling after coating the coating layer at a high temperature. On the surface of the coating layer of the conventional coated cutting chip, there are irregularities on the order of microns generated by crystal growth of the coating layer. Since the micron-order irregularities cause welding or the like, conventionally, removal by blasting or the like has been performed. When the blasting process was studied in detail, it was found that the use of coarse alumina particles having a mesh size of 150 mesh or less as the blasting projection particles broadens the crack width of the coating layer. Furthermore, it has been found that when this coated cutting tip is used for cutting, the work material enters the expanded crack, and the crack is developed, thereby reducing the fracture resistance of the coated cutting tip. Therefore, the present inventor has conducted research on the blasting process, and when the blasting process is performed using a fine hard ceramic powder as a medium, the coating layer can be further smoothed, and the width of cracks existing in the coating layer can be increased. I found that I could not expand.

That is, the coated cutting tip of the present invention is composed of a cutting tip base material made of a hard material and a coating layer having a thickness of 3 to 30 μm coated on the surface thereof, and the coating layer surface of the cutting edge ridge and rake face The arithmetic average roughness Ra with respect to the reference length of 5 μm is 0.15 μm or less, and the width of the cracks existing in the coating layer of the cutting edge ridge and the rake face is 0.10 μm or less.

The coated cutting tip of the present invention comprises a cutting tip base material made of a hard material, and a coating layer having a thickness of 3 to 30 μm coated on the surface thereof. The hard material of the present invention is a material that has been conventionally used as a base material for coated cutting chips, and specific examples thereof include cemented carbide, cermet, ceramics, and ultra-high pressure sintered body. Among these, cemented carbide has a good balance between wear resistance and fracture resistance, and is particularly preferable as a base material for the coated cutting tip of the present invention.

The surface of the cutting tip base material made of the hard material of the present invention is coated with a coating layer having a thickness of 3 to 30 μm. The coating layer of the present invention comprises at least one selected from the periodic table 4a, 5a, and 6a group elements, Al carbides, nitrides, oxides, and their mutual solid solutions. Specific examples include TiC, TiN, TiCN, TiCO, TiCNO, TiAlCNO, and Al ₂ O ₃ . When the thickness of the coating layer is less than 3 μm, the wear resistance is lowered, and when it exceeds 30 μm, the fracture resistance is lowered. Among them, 5 to 25 μm is preferable, and 10 to 20 μm is more preferable among them.

The inner layer other than the outermost layer of the coating layer of the present invention preferably includes an α-type Al ₂ O ₃ layer having a thickness of 0.5 to 20 μm. The reason why the preferable thickness of the α-type Al ₂ O ₃ layer is 0.5 to 20 μm is that when it is 0.5 μm or more, the oxidation resistance is improved and the crater wear resistance of the rake face is improved, and when the thickness exceeds 20 μm. This is because the chipping resistance of the cutting edge is lowered.

The coated cutting tip of the present invention has a rake face, a flank face, and a cutting edge ridge line portion. Specific examples of the cutting edge ridge line portion include a honing portion such as round honing, chamfer honing, and composite honing provided at a part or all of the intersection line between the rake face and the flank face. Specific examples of the rake face include lands, breakers, and boss faces on the rake face side connected to the cutting edge ridge line portion. Specifically as a flank, the side of the flank side connected to a cutting edge ridgeline part etc. can be mentioned.

By using fine hard ceramic particles and adjusting the blasting conditions such as blast pressure and blasting time, it is possible to leave the outermost layer of the rake face and the cutting edge ridge line part. That is, the surface material of the rake face and the cutting edge ridge line portion of the coated cutting tip of the present invention and the surface material of the flank face can be made the same substance. Among them, when the outermost layer of the coating layer of the present invention is a titanium compound composed of at least one selected from Ti and C, N, and O, it has a bright color appearance and is used as a cutting tip / This is particularly preferable because the unused corners can be easily identified. Specific examples of titanium compounds composed of Ti and at least one selected from C, N, and O include TiN and TiCN. Among them, TiN showing a golden color is more preferable.

  The arithmetic average roughness Ra with respect to the reference length of 5 μm of the cutting edge ridge line and the rake face of the coated cutting tip of the present invention is set to 0.15 μm or less. When Ra exceeds 0.15 μm, the work material is welded due to unevenness. This is because it tends to cause crimp separation damage and micro-scratch defect. However, when Ra is less than 0.05 μm, the coating surface and the work material are brought into close contact with each other, and the temperature of the tool edge is increased to promote crater wear. Therefore, Ra is preferably 0.05 to 0.15 μm. The arithmetic average roughness Ra for the reference length of 5 μm is measured by using an image analyzer from the surface roughness curve of the coating layer obtained by SEM observation of the coating layer cross-sectional structure of the rake face and the cutting edge ridge line portion. be able to.

In the coated cutting tip of the present invention, the width of the crack existing in the coating layer of the cutting edge ridge line portion and the rake face is set to 0.1 μm or less because when the thickness exceeds 0.1 μm, the welded work material enters the crack. This is to reduce the chipping resistance of the coated cutting tip. Although the crack width is preferably as small as possible, it is difficult to make the width less than 0.005 μm with the current manufacturing technology, and therefore the crack width has a lower limit of 0.005 μm. In addition, the width | variety of the crack which exists in the coating layer of a rake face and a cutting edge ridgeline part can be measured by observing the surface of a rake face and a cutting edge ridgeline part by SEM.

In the coated cutting tip of the present invention, it is preferable that the average crack interval of cracks existing in the cutting edge ridge line portion and the coating layer of the rake face is 100 μm or less. In the coated cutting tip of the present invention, the average crack interval means an average interval between one crack and a crack adjacent thereto. It is preferable that the average crack interval is 100 μm or less because the fracture resistance is further improved. However, since it is difficult to reduce the average crack interval to less than 10 μm with the current production technology, the average crack interval is preferably in the range of 10 to 100 μm, more preferably 10 to 60 μm. In addition, the average crack interval of the cracks existing in the coating layer of the rake face and the cutting edge ridge line portion is determined by etching the surface of the coating layer of the rake face and cutting edge ridge line portion with hydrofluoric acid so that the crack can be easily observed. The obtained coating layer surface can be obtained by enlarging the surface of the coating layer 50 times with an optical microscope and measuring the number of cracks crossing a straight line having a reference length of 2 mm.

  As one of the methods for producing the coated cutting chip of the present invention, a coated cutting chip having a surface of a cutting chip substrate coated with a coating layer having a thickness of 3 to 30 μm is prepared, and the surface is blasted with fine hard ceramic particles. A method can be mentioned. Specifically, a cutting tip substrate made of a hard material is prepared, and a coating layer having a thickness of 3 to 30 μm is coated on the surface thereof by chemical vapor deposition and / or physical vapor deposition. In the case of chemical vapor deposition, the average crack interval becomes narrower as the coating temperature is lower. The method of performing the wet blast process which projects the fine alumina particle of 800 mesh or more on the surface to the rake face and cutting edge ridgeline part of the obtained coated cutting chip can be mentioned. The outermost layer of the rake face, the cutting edge ridge line portion, and the flank face can be made the same substance by adjusting blasting conditions such as blast pressure and blasting time. In addition, the wet blast treatment is preferable because the media is projected more uniformly than the dry blast treatment, so that there is less variation in the coating layer thickness after the treatment.

The coated cutting tip of the present invention is highly effective in cutting work in which welding is likely to occur. Among them, excellent welding resistance is exhibited particularly when a workpiece such as ductile cast iron or low carbon steel that is likely to be welded during cutting is subjected to high speed cutting or heavy cutting such as high feed and high cutting.

Since the coated cutting tip of the present invention has a smooth surface, there is little welding. Moreover, since the width | variety of the crack which exists in a coating layer is narrow, the approach of a cut material into a crack can be prevented during cutting, and progress of a crack is suppressed. Due to such effects, the coated cutting tip of the present invention exhibits excellent cutting performance for a long time and realizes a long tool life.

As a base material, 91.5WC-0.5TiC-1.8TaC-0.2NbC-6.0Co type cemented carbide (JIS wt%) having a JIS standard CNMG120408 shape was prepared. The round honed portion was applied to the cutting edge ridge portion of the base material with a SiC brush, and then the base material surface was washed. For the inventive products 1 to 3 and the comparative products 1 to 7, an external heating chemical vapor deposition apparatus was used, a high purity gas of 99.5% by volume or more was used as the reaction gas, and the coating condition 1 shown in Table 1 On the surface of the hard alloy substrate, the thickness becomes 1.0 μm innermost layer TiN-9.0 μm columnar TiCN-0.5 μmTiAlCNO-5.0 μm α-type Al ₂ O ₃ -0.5 μm outermost layer TiN from the substrate side. A coating layer was coated. In addition, for inventions 4 and 5, an external heating chemical vapor deposition apparatus was used, a high-purity gas of 99.5% by volume or more was used as the reaction gas, and the cemented carbide substrate was used under the coating condition 2 shown in Table 2. The surface of the substrate is coated with a coating layer that becomes 1.0 μm innermost layer TiN-9.0 μm granular crystal TiCN-0.5 μm TiAlCNO-5.0 μm α-type Al ₂ O ₃ -0.5 μm outermost layer TiN from the substrate side. did.

The coated cemented carbides of the inventive products 1 to 5 and the comparative products 2 to 7 were subjected to a polishing process under the conditions shown in Table 3, and the coated cutting chips of the inventive products 1 to 3 and the comparative products 2 to 7 were obtained. . The coated cemented carbide of comparative product 1 was not subjected to any polishing treatment, and the coated cutting tip of comparative product 1 was used.

About the coated cutting tips of the inventive products 1 to 5 and the comparative products 1 to 7, the arithmetic average roughness Ra of the surface of the cutting edge ridge line portion and the rake face, the width of the crack existing in the coating layer of the cutting edge ridge line portion and the rake face, The surface material of the cutting edge ridge, the rake face and the flank, and the average crack interval between the cutting edge ridge and the rake face were measured, and the results are shown in Table 4. The arithmetic average roughness Ra of the surface of each part was calculated using an image processing apparatus by measuring the surface roughness curve by enlarging the polished cross section of each part 10,000 times with a scanning electron microscope. The width of the cracks present in the coating layer of each part was measured by enlarging the surface of each part by 50000 times with a scanning electron microscope. The average crack interval of each part is obtained by etching the surface of the coating layer of each part with hydrofluoric acid, enlarging the surface of the coating layer 50 times with an optical microscope, and measuring the number of cracks crossing a straight line with a reference length of 2 mm. Asked. Moreover, the surface material of each part was specified from surface observation and cross-sectional structure observation.

For the coated cutting tips of invention products 1 to 5 and comparative products 1 to 7, FCD700 (hardness: HB240) provided with four V-shaped grooves in a cylindrical shape was used as a work material, and cutting speed: Vc = 250 m / min, cutting: ap = 2 mm, feed: f = 0.3 mm / rev, intermittent cutting test is performed under the condition of using water-soluble cutting oil, until the corner wear after the cutting test reaches 0.4 mm, or The average value of the number of cutting passes until the cutting edge was damaged was measured five times, the damage state after the cutting test was observed, and the results are shown in Table 5.

From the results shown in Table 5, the coated cutting tips of Inventions 1 to 5 having Ra of the cutting edge ridge line portion and the rake face of 0.05 to 0.14 μm and the width of the crack of 0.06 to 0.10 μm are as follows. It can be seen that the number of cutting passes is 85 to 123 and the tool life is long. Among these, it can be seen that invention products 1 to 3 having an average crack interval of 45 to 61 μm are excellent in fracture resistance. In addition, the coated cutting tips of the inventive products 1 to 5 have TiN (golden) appearance of the entire chip including the cutting edge ridge line portion, the rake face and the flank face, and it is easy to determine whether the corner is used or not. .

  Comparative products 1 and 6 have a short life because Ra of the cutting edge ridge and the rake face is 0.20 to 0.64 μm, and comparative products 2 to 5 and 7 are cracks on the cutting edge ridge and the rake face. The width is 0.18 to 0.84 μm, so the life is short.

Claims (4)

Arithmetic average roughness with respect to a reference length of 5 μm of the coating layer surface of the cutting edge ridge line portion and the rake face composed of a cutting tip base material made of a hard material and a coating layer having a thickness of 3 to 30 μm coated on the surface thereof. Ra is 0.15 μm or less, and the width of cracks existing in the coating layer on the cutting edge ridge line and the rake face is 0.10 μm or less. The coated cutting tip according to claim 1, wherein the outermost layer of the coating layer is a titanium compound composed of Ti and at least one selected from C, N, and O. The coated cutting tip according to claim 1 or 2, wherein an average crack interval of cracks existing in the cutting edge ridge line portion and the coating layer of the rake face is 100 µm or less. The coated cutting tip according to any one of claims 1 to 3, wherein the hard material is a cemented carbide.