Surface-coated cutting tool with coated film having strength distribution of compressive stress

{
  "publication_number": "US7799415B2",
  "country": "US",
  "kind": "B2",
  "title": "Surface-coated cutting tool with coated film having strength distribution of compressive stress",
  "abstract": "A surface-coated cutting tool according to the present invention includes a base material and a coated film formed on the base material. The coated film serves as an outermost layer on the base material and has compressive stress. The compressive stress is varied so as to have strength distribution in a direction of thickness of the coated film. The strength distribution is characterized in that the compressive stress at a surface of the coated film continuously decreases from the surface of the coated film toward a first intermediate point located between the surface of the coated film and a bottom surface of the coated film and the compressive stress attains a relative minimum point at the first intermediate point.",
  "claims": [
    "1. A surface-coated cutting tool, comprising: a base material; and a coated film formed on said base material; wherein said coated film serves as an outermost layer on said base material and has compressive stress, said compressive stress is varied so as to have strength distribution in a direction of thickness of said coated film, and said strength distribution is characterized in that the compressive stress at a surface of said coated film continuously decreases from said surface of said coated film toward a first intermediate point located between said surface of said coated film and a bottom surface of said coated film and the compressive stress attains a relative minimum point at said first intermediate point.",
    "2. The surface-coated cutting tool according to claim 1, wherein said strength distribution is characterized in that a maximum compressive stress is attained at said surface of said coated film and the compressive stress maintains a constant value from said first intermediate point to said bottom surface of said coated film.",
    "3. The surface-coated cutting tool according to claim 2, wherein said compressive stress of the entire coated film is stress in a range from at least −15 GPa to at most 0 GPa.",
    "4. The surface-coated cutting tool according to claim 2, wherein said first intermediate point is located at a position distant from said surface of said coated film by at least 0.1% to at most 50% of the thickness of said coated film.",
    "5. The surface-coated cutting tool according to claim 2, wherein said compressive stress at said first intermediate point is set to a value comparable to 20 to 90% of the compressive stress at said surface of said coated film.",
    "6. The surface-coated cutting tool according to claim 5, wherein said compressive stress at said first intermediate point is set to a value comparable to 40 to 80% of the compressive stress at said surface of said coated film.",
    "7. The surface-coated cutting tool according to claim 2, wherein said compressive stress attains maximum at said surface of said coated film, the maximum compressive stress is maintained across a prescribed distance from said surface of said coated film toward said first intermediate point, and thereafter said compressive stress continuously decreases toward said first intermediate point.",
    "8. The surface-coated cutting tool according to claim 1, wherein said strength distribution is characterized in that said compressive stress continuously increases from said first intermediate point toward said bottom surface of said coated film.",
    "9. The surface-coated cutting tool according to claim 8, wherein said compressive stress of the entire coated film is the stress in a range from at least −15 GPa to at most 0 GPa.",
    "10. The surface-coated cutting tool according to claim 8, wherein said first intermediate point is located at a position distant from said surface of said coated film by at least 0.1% to at most 50% of the thickness of said coated film.",
    "11. The surface-coated cutting tool according to claim 8, wherein said compressive stress attains maximum at said surface of said coated film.",
    "12. The surface-coated cutting tool according to claim 8, wherein said compressive stress at said first intermediate point is set to a value comparable to 20 to 90% of the compressive stress at said surface of said coated film.",
    "13. The surface-coated cutting tool according to claim 12, wherein said compressive stress at said first intermediate point is set to a value comparable to 40 to 80% of the compressive stress at said surface of said coated film.",
    "14. The surface-coated cutting tool according to claim 8, wherein said compressive stress at said surface of said coated film is maintained across a prescribed distance from said surface of said coated film toward said first intermediate point, and thereafter said compressive stress continuously decreases toward said first intermediate point.",
    "15. The surface-coated cutting tool according to claim 1, wherein said strength distribution is characterized in that said compressive stress continuously increases from said first intermediate point toward a second intermediate point located between said first intermediate point and said bottom surface of said coated film and attains a relative maximum point at said second intermediate point.",
    "16. The surface-coated cutting tool according to claim 15, wherein said compressive stress of the entire coated film is the stress in a range from at least −15 GPa to at most 0 GPa.",
    "17. The surface-coated cutting tool according to claim 15, wherein said first intermediate point is located at a position distant from said surface of said coated film by at least 0.1% to at most 50% of the thickness of said coated film.",
    "18. The surface-coated cutting tool according to claim 15, wherein said second intermediate point is located at a position distant from said surface of said coated film by at least 0.2% to at most 95% of the thickness of said coated film.",
    "19. The surface-coated cutting tool according to claim 15, wherein said compressive stress attains maximum at said surface of said coated film.",
    "20. The surface-coated cutting tool according to claim 15, wherein said compressive stress at said first intermediate point is set to a value comparable to 20 to 90% of the compressive stress at said surface of said coated film.",
    "21. The surface-coated cutting tool according to claim 20, wherein said compressive stress at said first intermediate point is set to a value comparable to 40 to 80% of the compressive stress at said surface of said coated film.",
    "22. The surface-coated cutting tool according to claim 15, wherein said compressive stress at said surface of said coated film is maintained across a prescribed distance from said surface of said coated film toward said first intermediate point, and thereafter said compressive stress continuously decreases toward said first intermediate point.",
    "23. The surface-coated cutting tool according to claim 1, wherein said strength distribution is characterized in that said compressive stress continuously increases from said first intermediate point toward a second intermediate point located between said first intermediate point and said bottom surface of said coated film and attains a relative maximum point at said second intermediate point, and said strength distribution has one or more similar said relative minimum point between said second intermediate point and said bottom surface of said coated film.",
    "24. The surface-coated cutting tool according to claim 23, wherein said strength distribution has one or more similar said relative maximum point between said second intermediate point and said bottom surface of said coated film.",
    "25. The surface-coated cutting tool according to claim 23, wherein said strength distribution has one or more said similar relative minimum point and one or more said similar relative maximum point in an alternate and repeated manner in this order between said second intermediate point and said bottom surface of said coated film.",
    "26. The surface-coated cutting tool according to claim 23, wherein said compressive stress of the entire coated film is the stress in a range from at least −15 GPa to at most 0 GPa.",
    "27. The surface-coated cutting tool according to claim 23, wherein said first intermediate point is located at a position distant from said surface of said coated film by at least 0.1% to at most 40% of the thickness of said coated film.",
    "28. The surface-coated cutting tool according to claim 23, wherein said second intermediate point is located at a position distant from said surface of said coated film by at least 0.2% to at most 80% of the thickness of said coated film.",
    "29. The surface-coated cutting tool according to claim 23, wherein said compressive stress attains maximum at said surface of said coated film.",
    "30. The surface-coated cutting tool according to claim 23, wherein said compressive stress at said first intermediate point is set to a value comparable to 10 to 80% of the compressive stress at said surface of said coated film.",
    "31. The surface-coated cutting tool according to claim 30, wherein said compressive stress at said first intermediate point is set to a value comparable to 20 to 60% of the compressive stress at said surface of said coated film.",
    "32. The surface-coated cutting tool according to claim 23, wherein said compressive stress at said surface of said coated film is maintained across a prescribed distance from said surface of said coated film toward said first intermediate point, and thereafter said compressive stress continuously decreases toward said first intermediate point."
  ],
  "description_excerpt": "The present invention relates to a cutting tool such as a drill, an end mill, a throw away tip for a drill, a throw away tip for an end mill, a throw away tip for milling, a throw away tip for turning, a metal saw, a gear cutting tool, a reamer, and a tap, and more particularly to a surface-coated cutting tool having a coated film for improving characteristics such as wear resistance formed on its surface (an outermost layer).\n\nConventionally, a hardmetal (a WC - Co alloy or an alloy obtained by adding a carbonitride of Ti (titanium), Ta (tantalum), Nb (niobium), or the like to the WC - Co alloy) has been used for a cutting tool. With a growing tendency toward high-speed cutting in recent years, a hard alloy tool has more increasingly been used, the hard alloy tool being obtained by coating a surface of a base material such as a hardmetal, cermet or ceramics based on alumina or silicon nitride with a coated film composed of a carbide, a nitride, a carbonitride, a boronitride, and an oxide of IVa-, Va- and VIa-group metal in the element periodic table or Al (aluminum) to a thickness of 3 to 20 μm, with the use of CVD (Chemical Vapor Deposition) or PVD (Physical Vapor Deposition).\n\nIn particular, as coating by means of PVD can improve wear resistance without deteriorating strength of the base material, it is widely used for a cutting tool in which strength is required, such as a drill, an end mill, and a throw away tip for milling or turning.\n\nRecently, in order to further improve efficiency in a cutting process, a cutting speed has been increased. With such a tendency, further wear resistance is required in the tool.",
  "cpc": [
    "C23C 30/005",
    "B23B 51/00",
    "B23C 5/16",
    "C23C 14/06",
    "C23C 14/0641",
    "Y10T 428/24",
    "Y10T 428/24992",
    "Y10T 428/31"
  ],
  "ipc": [
    "B23B 27/14",
    "B32B 9/00"
  ],
  "assignees": [
    "Sumitomo Electric Hardmetal Corp",
    "Sumitomo Electric Industries Ltd"
  ],
  "inventors": [
    "Hideki Moriguchi",
    "Haruyo Fukui",
    "Shinya Imamura",
    "Koji Yamaguchi",
    "Junji Iihara"
  ],
  "filing_date": "2005-07-01",
  "publication_date": "2010-09-21",
  "grant_date": "2010-09-21",
  "priority_date": "2004-07-08",
  "family_id": "35783772",
  "cited_by_count": 4,
  "citations": [
    "US6066399A",
    "JP2001315006A",
    "JP2001353603A",
    "JP2003113463A",
    "WO2006009121A1"
  ]
}