Polycrystalline cubic boron nitride abrasive and process for pre

Details Polycrystalline cubic boron nitride abrasive and process for pre Polycrystalline cubic boron nitride abrasive and process for pre

1979-06-11

1981-09-15

Czaja, Donald E.

Abrasive tool making process, material, or composition

With inorganic material

51288, 51309, 423290, B24D 328

Patent

active

042895030

ABSTRACT:
Cubic boron nitride has been made from powdered hexagonal boron nitride by a process which comprises vacuum firing of the HBN and conversion by high pressure-high temperature processing at 55-80 kilobars and 1600.degree. C. to the reconversion temperature.
The high pressure reaction cell has a special design which prevents the entrance of impurities into the sample. This cell, referring to FIG. 2, comprises, for example, a carbon tube (8) enclosing concentric titanium sleeve (9). Within the cylinder defined by the tube and sleeve are: the HBN sample (4), carbon filler (3), shielding tantalum foil discs (2) and carbon end plugs (10).
The vacuum firing is done at pressures of 10.sup.-5 --10.sup.-10 mm Hg, 1400.degree.-1900.degree. C., for 5 minutes--4 hours, and is believed to form a thin, free-boron coating on the HBN particles.
The process works on both pyrolytic (turbostratic) and graphitic hexagonal boron nitride.
Grinding grits formed by milling cubic boron nitride chunks recovered from the high pressure-high temperature process have resulted in higher grinding ratios than commercially available CBN.

REFERENCES:
patent: 3212852 (1965-10-01), Bundy
patent: 3212852 (1965-10-01), Bundy
patent: 3645706 (1972-02-01), Bovenkerk
patent: 3918931 (1975-11-01), De Uries et al.
patent: 3926571 (1975-12-01), Labossier et al.
patent: 4008055 (1977-02-01), Phaal
patent: 4089931 (1978-05-01), Sharma et al.

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