Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C30/00—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process
  • C23C30/005—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process on hard metal substrates

Definitions

• the present invention relates to blade members of tungsten carbide (WC)-based cemented carbide having hard coatings formed by chemical vapor deposition, and particularly, those members which exhibit excellent performance when used in severe cutting operations such as milling operations accompanying thermal shock.
• WC tungsten carbide
• Known WC-based cemented carbide blade members which comprise hard coatings formed on the substrates by chemical vapor deposition and including one or more layers each composed of one of carbides, nitrides and oxides of metals in groups IV A , V A and VI A of the Periodic Table, solid solutions of these compounds and aluminum oxide, are utilized mainly in turning operations since they possess both the toughness inherent in the cemented carbide substrates as well as the wear resistance inherent in the hard coatings.
• Japanese Patent Application B2-Publication, Serial No. 58-26428 describes a cemented carbide blade member for use in processing requiring great fracture resistance. In this blade member, a cobalt enriched portion, which exhibits great toughness, is formed in the substrate so as to be adjacent to the substrate surface thereof.
• the cutting tools are subjected not only to the mechanical shock but also to the thermal shock caused by heating and/or cooling, and hence it is very difficult to avoid cracking of the hard coatings.
• the cemented carbide blade member as disclosed in the above published Patent Application, since the surface portion of the substrate and the interior portion thereof are characteristically different, cracking caused by the thermal shock develops at the interface between the surface portion and the interior portion, resulting in fracturing.
• Japanese Patent Application A-Publication, Serial No. 54-73392 disclosed the inclusion of free carbons in the WC-based cemented carbide substrate to prevent the propagation of the crack.
• a blade member of tungsten carbide based cemented carbide with a hard coating comprising a substrate of tungsten carbide based cemented carbide and a hard coating of at least one coating layer deposited on the substrate, the substrate consisting of a binder phase of 5 to 13% by weight of cobalt, and a hard dispersed phase of no greater than 17 % by weight of hard-phase constituents, and a balance tungsten carbide, the coating layer being formed of one substance selected from the group consisting of a carbide, a nitride and an oxide of a metal in IV A , V A and VI A of the Periodic Table, the substrate being such that a parameter R, cal/(cm)(sec), defined by ( ⁇ x ⁇ )/( ⁇ x E ) and representing thermal shock resistance of the substrate takes a value of no less than 100, wherein ⁇ , ⁇ , ⁇ and E denote thermal conductivity, transverse rupture strength, coefficient of thermal expansion and Young'
• the inventors have made an extensive study in order to obtain a blade member of tungsten carbide based cemented carbide which meets the requirements as described above. As a result, they have come to know that a parameter R, defined by ( ⁇ x ⁇ )/( ⁇ x E ) and representing thermal shock resistance of the substrate, wherein ⁇ , ⁇ , ⁇ and E denote thermal conductivity, transverse rupture strength, coefficient of thermal expansion and Young's modulus of the substrate, respectively, has a correlation with fracture resistance in the milling operations. More specifically, in a cemented carbide blade member without hard coating, the increase of value of the above parameter R representing the thermal shock resistance, results in the deterioration of the wear resistance, so that the tool life becomes unduly short.
• the inventors have found that when a hard coating is formed on a substrate of tungsten carbide-based cemented carbide which takes a value of R of no less than 100 cal/(cm)(sec), the resulting surface coated blade member become less susceptible to fracturing during milling operations and have high wear resistance.
• the present invention is based on the above findings, and provides a blade member of tungsten carbide based cemented carbide with a hard coating which comprises a substrate of tungsten carbide-based cemented carbide and a hard coating of one or more coating layers deposited thereon.
• Each coating layer is formed of one substance selected from the group consisting of a carbide, a nitride and an oxide of a metal in IV A , V A and VI A of the Periodic Table.
• the thickness of the hard coating ranges from 2 to 7 ⁇ m. If the thickness is below 2 ⁇ m, the wear resistance is deteriorated. On the other hand, if the thickness exceeds 7 ⁇ m, the blade member is susceptible to fracturing.
• the interior portion of the cemented carbide substrate has Rockwell "A" hardness, HRA, ranging from 88.0 to 91.0. If the hardness HRA is less than 88.0, the wear resistance of the blade member is deteriorated. On the other hand, if the hardness HRA exceeds 91.0, the resulting blade member becomes inferior in fracture resistance.
• the cemented carbide substrate has cobalt content of 5 to 13 % by weight. If the cobalt content is less than 5 % by weight, the toughness is reduced. On the other hand, if the cobalt content exceeds 13 % by weight, the blade member may be subjected to chipping, due to the adhesion of workpiece.
• the hard phase of the constituents other than balance WC e.g., TiC, TaC and so on, is present in an amount no greater than 17 % by weight. If the total content of such hard phase constituents exceeds 17 % by weight, a lot of cracking develops due to thermal shock, such that the chipping resistance of the cutting edge is deteriorated.
• the blade member of tungsten carbide based cemented carbide with a hard coating in accordance with the present invention exhibits excellent thermal shock resistance even when used for milling operations under the severe conditions accompanying thermal shock.
• cutting inserts having ISO standards of SEEN1203AFTN1 were prepared using the above WC-based cemented carbides a to e , and hard coatings as shown in Table 2 were formed on the surfaces thereof by means of chemical vapor deposition to provide surface coated blade members 1 to 8 of the invention and comparative surface coated blade members 9 to 12.

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Vapour Deposition (AREA)
• Cutting Tools, Boring Holders, And Turrets (AREA)
• Other Surface Treatments For Metallic Materials (AREA)
• Physical Vapour Deposition (AREA)

Applications Claiming Priority (2)

Publications (2)

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Family Applications (1)

Country Status (2)

Cited By (4)

Citations (5)

• 1990
  • 1990-11-20 JP JP31487490A patent/JPH04189401A/ja active Pending
• 1991
  • 1991-11-19 EP EP19910119676 patent/EP0487008A3/en not_active Withdrawn

Patent Citations (5)

Non-Patent Citations (1)

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