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Cubic Boron Nitride Compact

Inactive Publication Date: 2008-12-11
GOUDEMOND IAIN PATRICK +2
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0042]According to a second embodiment of this aspect of the invention, there is provided a high cBN content PCBN compact (with a cBN content exceeding 75 volume %), particularly a high content CBN PCBN compact as described above, with enhanced Electric Discharge (ED) Machining or Grinding cuttability such that it may be cut using EDM or EDG techniques at speeds of at least 50% better than those typically obtained for conventional PCBN materials with similar cBN contents whilst still achieving an acceptable surface finish.

Problems solved by technology

Laser cutting is not the generally preferred method due to high degree of surface damage, higher costs and longer cutting times especially when cutting ‘solid’ (unbacked) PCBN inserts.
The workpiece is eroded by electric discharges or sparks which on a small scale generate localised shock waves and intense heat.
High cBN PCBN materials have particularly poor EDM-cuttability because of the constituent high levels of cBN, which is electrically non-conductive.
However, this tends to degrade overall composite properties by reducing the amount of the effective cBN phase and hence negatively impacting on performance.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

Attrition Milling

[0060]Cobalt, aluminium, tungsten powders, with the average particle size 1, 5 and 1 μm, respectively, were attrition milled with CBN. Cobalt, 33 wt %, aluminium, 11 wt %, and tungsten, 56 wt %, form the binder mixture. Cubic boron nitride (CBN) powder of about 1.2 μm in average particle size was added in to the binder mixture in an amount to achieve 92 volume percent CBN. The powder mixture was attrition milled with hexane for 2 hours using cemented carbide milling media. After attrition milling, the slurry was dried under vacuum and formed into a green compact supported by a cemented carbide substrate. After vacuum outgassing, the material was sintered at about 5.5 GPa and at about 1480° C. to produce a polycrystalline CBN compact. This CBN compact (hereinafter referred to as Material A) was analysed and then subjected to a machining test.

example 2

Attrition Milling

[0061]Aluminium and tungsten powders, with the average particle size about 5 and 1 μm, respectively, were attrition milled with CBN. Aluminium, 30 wt %, and tungsten, 70 wt %, form the binder mixture. Cubic boron nitride (CBN) powder of about 2 μm in average particle size was added in to the binder mixture in an amount to achieve 94.5 volume percent CBN. The powder mixture was attrition milled with hexane for 2 hours using cemented carbide milling media. After attrition milling, the slurry was dried under vacuum and formed into a green compact supported by a cemented carbide substrate. After vacuum outgassing, the material was sintered at about 5.5 GPa and at about 1480° C. to produce a polycrystalline CBN compact. This CBN compact (hereinafter referred to as Material B) was analysed and then subjected to a machining test.

example 3

Attrition Milling

[0062]Aluminium and cobalt powders, with the average particle size about 5 and 1 μm, respectively, were attrition milled with CBN. Aluminium, 30 wt %, and cobalt, 70 wt %, form the binder mixture. Cubic boron nitride (CBN) powder of about 2 μm in average particle size was added in to the binder mixture in an amount to achieve 93 volume percent CBN. The powder mixture was attrition milled with hexane for 2 hours using cemented carbide milling media. After attrition milling, the slurry was dried under vacuum and formed into a green compact supported by a cemented carbide substrate. After vacuum outgassing, the material was sintered at about 5.5 GPa and at about 1480° C. to produce a polycrystalline CBN compact. This CBN compact (hereinafter referred to as Material C) was analysed and then subjected to a machining test.

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PUM

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Abstract

A polycrystalline cubic boron nitride compact which comprises greater than 75 volume % and not greater than 90 volume % cubic boron nitride particles, the cubic boron nitride particles comprising particles of at least two average particle sizes, and a binder phase constituting the balance of the compact and comprising at least one titanium compound selected from titanium boride, titanium nitride, titanium carbide and titanium carbonitride and at least one aluminium compound selected from aluminium oxide, aluminium boride, aluminium nitride, aluminium carbide and aluminium carbonitride.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation-in-part of U.S. patent application Ser. No. 12 / 091,532 which is a 371 filing of International Patent Application Number PCT / IB2006 / 003023 filed Oct. 27, 2006 and entitled “Cubic Boron Nitride Compact” and which claims priority benefits of South African Patent Application Number 2005 / 0766 filed Oct. 28, 2005, the disclosures of which are hereby incorporated by reference.BACKGROUND OF THE INVENTION[0002]This invention relates to polycrystalline cubic boron nitride abrasive compacts and the manufacture thereof.[0003]Boron nitride exists typically in three crystalline forms, namely cubic boron nitride (CBN), hexagonal boron nitride (hBN) and wurtzitic cubic boron nitride (wBN). Cubic boron nitride is a hard zinc blende form of boron nitride that has a similar structure to that of diamond. In the CBN structure, the bonds that form between the atoms are strong, mainly covalent tetrahedral bonds. Methods for pr...

Claims

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Application Information

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IPC IPC(8): B24D3/06
CPCB24D3/06
Inventor GOUDEMOND, IAIN PATRICKCAN, NEDRETANDERSIN, STIG AKE
Owner GOUDEMOND IAIN PATRICK
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