Coating processes – Direct application of electrical – magnetic – wave – or... – Plasma
Patent
1996-09-04
1998-03-03
Pianalto, Bernard
Coating processes
Direct application of electrical, magnetic, wave, or...
Plasma
2041921, 427249, 427294, H05H 124
Patent
active
057231885
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to the field of producing wear-resistant layers or producing layers with particular wear properties. It relates to a process for producing wear-resistant layers of cubic boron nitride (cBN) or bonding layers with a high cBN content.
Thermodynamically unstable cBN is distinguished by a high degree of hardness surpassed only by diamond and has other properties which are similar to those of diamond. Particular among these are favorable thermal conductivity, excellent tribological properties, and not least, favorable transparency in the visible range (n=2.2), as well as an extremely large band gap of >6.4 eV, by means of which cBN also possesses a high potential as a semiconductor material.
In the field of manufacturing technology, cBN has the significant advantage in comparison to diamond in that it is inert in relation to steel and consequently permits the processing of workpieces that contain iron. This important production area is not accessible to diamond tools because of the chemical wear on diamond.
Since the 80s, when chiefly Japanese and American scientists fundamentally proved that the cubic phase of boron nitride can also be produced with the aid of plasma-activated processes, there have been a large number of endeavors throughout the world to produce cBN layers.
Thus the manufacture of cBN layers is described, for example, in the "Journal of Applied Physics" 72(2), 15 Jul. 1992, p. 504 and in the "journal of Material Research" Vol. 8, no. 6, June 1993, wherein an ion beam Assisted Deposition System (IBAD) came into use.
Furthermore, in "Diamond and Related Materials" 2 (1993), p. 512, a process is described, which functions with the aid of ion beam cannons, wherein an ion source is used for atomizing the target comprised of boron or hexagonal boron nitride (hBN) and a second ion cannon carries out the bombardment of the film supported on a substrate.
Furthermore, in "Surface and Coating Technology" 43/44 (1990), pp. 145-153, a reactive ion plating process is described, in which boron is vaporized with the aid of an electron beam vaporizer in an Ar/N.sub.2 atmosphere, which is additionally ionized. The layer formed is disposed on a substrate retainer with negative potential so that the growing layer is bombarded with the Ar and N.sub.2 ions present.
In the process described in "Thin Solid Films" 224 (1993), pp. 46-51, the manufacture of cBN layers is executed with the aid of an ion-assisted laser pulse deposition. An hBN target is used. The ion bombardment is carried out by applying a direct-current potential.
The process described in the "Japanese Journal of Applied Physics" Vol. 30, no. 2, Feb. 1991, pp. 344-348 works with a microwave discharged at the electron cyclotron resonance condition (ECR) wherein boron nitride (BN) is constituted from the gas phase Ar/N.sub.2 /B.sub.2 H.sub.6 and an RF bias (radio frequency bias voltage) is applied to the substrate.
Finally, a process for producing cBN-containing layers is also demonstrated in the "Japanese Journal of Applied Physics" Vol. 29, no. 7, July 1990, pp. 1175-1177, in which an hBN target is atomized in an inert high frequency plasma (HF plasma). The substrate is likewise kept at a negative potential with an HF bias so that a bombardment with Ar ions occurs.
For the sake of completeness, please refer to German Patent Disclosure 38 10 237, U.S. Pat. No. 4,412,899, U.S. Pat. No. 4,415,420, U.S. Pat. No. 4,683,043, and U.S. Pat. No. 5,096,740, which likewise disclose different processes for producing cBN layers or cBN-containing layers.
The (Physical Vapor Deposition) processes described in the prior art uniformly use either boron or hexagonal boron nitride (hBN) as the target or vaporization material. With regard to an economical use, all of these processes possessed considerable disadvantages. So with these processes, only relatively small surfaces can be coated at low deposition rates.
The known CVD-ECR (Chemical Vapor Deposition-Electron Cyclotron Resonance) processes have the considerable di
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Kester et al., "Phase Evolution in Boron Nitride Thin Films", Journal of Material Research, vol. 8, No. 6, Jun. 1993, pp. 1213-1216.
Tanabe et al., "Influence of Sputtering Target Material on the Formation of Cubic BN Thin Films by Ion Beam Enhanced Deposition", Diamond and Related Materials, 2 (1993), pp. 512-516. (No month avail.).
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International Search Report.
International Preliminary Examination Report.
Bewilogua Klaus
Daaud Simone
Luthje Holger
Fraunhofer-Gesellschaft zur Forderung der Angewandten Forschung
Pianalto Bernard
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