Composite hard metal body and process for its production

Specialized metallurgical processes – compositions for use therei – Compositions – Consolidated metal powder compositions

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75232, 75233, 75234, 75235, 75236, 75237, 75238, 75239, 75240, 75241, 75244, 419 12, 419 13, 419 14, 419 15, 419 16, 419 17, 419 18, 419 19, 419 31, 419 32, 419 33, 419 35, 419 49, 419 53, 419 55, 419 68, B22F 300

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051731070

DESCRIPTION:

BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Phase of PCT/DE 89/00740 filed Nov. 27, 1989 and based, in turn upon German National Applications P 38 42 439.8 filed Dec. 16, 1988 and P 38 43 219.6 filed Dec. 22, 1988 under the International Convention.


FIELD OF THE INVENTION

The invention relates to a composite hard metal body, consisting of phases of hard material, such as tungsten carbide and/or carbides, or nitrides of elements of the Group IVb or Group Vb of the classification of elements, of reinforcing materials and of a binder metal phase such as cobalt and/or iron and/or nickel, and to a process for producing the composite hard metal body by methods of powder metallurgy.


BACKGROUND OF THE INVENTION

Monocrystal materials known in the art have outstanding mechanical characteristics, such as tensile and shearing strength.
Austrian Patent 259 242 describes a sintered hard metal consisting of hard materials and binders, containing hard materials in the form of needle-shaped monocrystals in an amounts of at least 0.1%, preferably 0.5 to 1.5% of the entire content of hard materials. In order to produce these sintered hard metals, WC in the form of needle-shaped monocrystals is added to the hard-material component prior to grinding. After the addition of a binder from the iron group, the hard metal mixture is pressed and sintered with the formation of a liquid phase. However, it is disadvantageous that the monocrystalline WC dissolves to a great extent in the binder phase (compare German publication "Metall", July 1974, Part 7). The hard-metal monocrystals are not able to achieve a noticeable improvement of wear resistance, especially because the maximum amount of hard-metal monocrystals to be added is set by the proportion of grains of hard material (grains with a mean diameter of less than 2 .mu.m) to be replaced.


OBJECTS OF THE INVENTION

It is an object of the present invention to provide a composite hard metal body having improved toughness, improved hardness even under a high thermal load and a lower susceptibility to fracture.
Furthermore, it is an object of the present invention to provide an improved process for the production of such a composite hard metal body.


SUMMARY OF THE INVENTION

These objects are attained periodic with a composite hard metal body having a composition consisting of phases of hard material, such as tungsten carbide and/or carbides or nitrides of the elements of Groups IVb or Vb of the classification of elements, of reinforcing materials and of a binder metal phase such as cobalt and/or iron and/or nickel. The body includes either a monocrystalline platelet-shaped reinforcing material made of borides and/or carbides and/or nitrides and/or carbonitrides of the elements of Group IVb (Ti, Zr, Hf), Vb (V, Nb, Ta) or VIb (Cr, Mo, W) or mixtures thereof and/or of SiC, Si.sub.3 N.sub.4, Si.sub.2 N.sub.2 O, Al.sub.2 O.sub.3, ZrO.sub.2, AlN and/or BN and/or monocrystalline needle-shaped reinforcing material made of SiC, Si.sub.3 N.sub.4, Si.sub.2 N.sub.2 O, Al.sub.2 O.sub.3, ZrO.sub.2, AlN, and/or BN.
The proportion of the reinforcing materials is between 2 to 40% by volume, preferably 10 to 20% by volume.
Another object of the present invention is to provide a process for the production of such a composite hard metal body. The composite body according to the invention can thus have two kinds of reinforcement materials, monocrystalline platelet-shaped materials known as platelets and monocrystalline needle-shaped materials i.e. whiskers, sometimes also filaments. The platelets include borides, carbides, nitrides and/or carbonitrides of elements of the Groups IVb to VIb, SiC, Si.sub.3 N.sub.4, Si.sub.2 N.sub.2 O, Al.sub.2 O.sub.3, ZrO.sub.2, AlN and/or BN or mixtures of the aforementioned platelets.
The whiskers are SiC, SiC, Si.sub.3 N.sub.4, Si.sub.2 N.sub.2 O, Al.sub.2 O.sub.3, ZrO.sub.2, AlN and/or BN or mixtures of the aforementioned whiskers.
The use of needle-shaped monocrystals or whiskers, has already been proposed in other materials. For i

REFERENCES:
patent: 4007049 (1977-02-01), Rossi et al.
patent: 4259112 (1981-03-01), Dolowy et al.
patent: 4463058 (1984-07-01), Hood et al.
patent: 4756791 (1988-07-01), D'Angelo et al.
M. Futamoto et al Journal of Crystal Growth 61(1983) pp. 69-74 Hafnium Carbide and Nitride Whisker Growth By Chemical Vapor Deposition.
Von Gunter Nitschmann, Wetzlar VDI-Z 107 (1965) Nr.23 August (II) pp. 1133-1134 Verbundwerkstoffe mit Whiskern.
Kubota Tekko K.K.(1) / Hisashi Hiraishi(5) 59-107059 (A) Appl. No. 57-215942 Heat-Resistant Ceramic Material.
Mitsubishi Kinzoku K.K. 59-190339(A) Appl. No. 58-63436 Manufacture of Superhard Cermet For Cutting Tool With High Toughness.
S. Motojima et al Journal of Crystal Growth 87 (1988) pp. 311-317 Chemical Vapour Growth of B-Sic Whiskers From A Gas Mixture Of . . . .
H. Grewe et al Whiskerverstarkte Keramiken In: cfi/Ber. DKG 8/9-87, pp. 303, 306-308, 313-317.
A. P. Levitt; Whisker Technology In Chemical Engineering Progress, vol. 62, No. 3; Mar. 1966, pp. 51-67.

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