Metal treatment – Process of modifying or maintaining internal physical... – Treating loose metal powder – particle or flake
Patent
1993-08-18
1995-11-14
Walsh, Donald P.
Metal treatment
Process of modifying or maintaining internal physical...
Treating loose metal powder, particle or flake
419 68, 419 61, B22F 100
Patent
active
054663105
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention concerns the production of metal and solid metalloid nitrides, and also the production of metallic composites in the form of a metal matrix with particles of a metal or metalloid nitride dispersed within the matrix. More particularly, it concerns the synthesis of metal and metalloid nitrides and composites of metal with a dispersed phase of a metal or metalloid nitride, using mechanical alloying techniques.
BACKGROUND
Nitrides of elemental metals and metalloids (such as silicon) are usually very hard materials with high temperature stability, high thermal conductivity and high corrosion resistance. They are used, inter alia, as abrasives and as additives which increase the strength and hardness of metals and alloys used as cutting tools.
Nitrides are difficult to synthesise. Usually they are produced by a chemical nitration reaction. However, such chemical nitration processes are generally expensive and invariably yield mixtures of nitrides, with uncertain properties. For example, in the chemical production of tungsten nitride, the product is usually a mixture of the nitrides W.sub.2 N and WN. Similarly, molybdenum nitride production and iron nitride production usually yield mixtures of, respectively, Mo.sub.2 N+MoN, and Fe.sub.2 N+Fe.sub.4 N.
Using current chemical nitration processes, it is extremely difficult, if not impossible, to produce a composite material comprising a metal matrix material having within it a dispersed nitride phase (for example titanium and titanium nitride, Ti+TiN).
Another technique for producing metal nitrides involves a direct reaction between the metal and nitrogen at high temperature and pressure. In one implementation of this technique, metal powder is annealed in a nitrogen atmosphere at high temperatures (about 1500.degree. C.) for a long time. Usually the nitrogen is caused to flow through the metal powder throughout this process. The main disadvantages of this technique are (i) the fact that many metals do not react with nitrogen directly, even at high temperatures, so that the use of this technique is limited; and (ii) in many instances, a "plug" of the nitride is formed at the nitrogen input side of the powder and this plug restricts the flow of nitrogen, thus preventing the formation of the metal nitride throughout the metal powder. Hence this technique (as is the case with the alternative techniques of ion nitriding, salt bath nitriding, and deposition nitriding) produces metals with nitride coatings rather than bulk metal nitrides.
DISCLOSURE OF THE PRESENT INVENTION
It is an object of the present invention to provide a new, relatively inexpensive, and reliable method of producing (a) metal and solid metalloid nitrides and (b) composites which consist of a matrix of metal or metal alloy having dispersed therein a quantity of a metal or metalloid nitride. To achieve this objective, a metal or solid metalloid powder is subjected to ball milling (preferably high intensity ball milling using a ball mill of the type described in the specification of International patent application No PCT/AU90/00471) in an atmosphere of nitrogen or in an atmosphere (such as ammonia) which contains nitrogen. The quantity of nitrogen in the ball mill is controlled to ensure that a required product is obtained (for example, a single phase consisting of a nitride, or a mixture of a metal and its nitride, or a single phase solid solution of a metal and its nitride). The nitrogen may be at atmospheric pressure but is preferably at a pressure in the range of from 1 atmosphere (approximately 100 kPa) to 50 atmospheres (approximately 5,000 kPa). However, the nitrogen pressure (that is, the pressure within the ball mill) may be higher than 50 atmospheres, an upper limit being about 1 MPa. The milling may be performed at room temperature or at elevated temperatures. The time required to produce a specific nitride will depend upon the metal or alloy to be nitrided, the pressure of nitrogen, the temperature at which the milling is performed, and the milling mode
REFERENCES:
patent: 3011927 (1961-12-01), Zelezny
patent: 3459546 (1969-08-01), Lambert
patent: 3615380 (1971-10-01), Fichte et al.
patent: 3741733 (1973-06-01), Kieffer
patent: 3880600 (1975-04-01), Zboril
patent: 3904448 (1975-09-01), Takahashi et al.
patent: 4063938 (1977-12-01), Weissman
Goetzel, C. G., "Treatise on Powder Metallurgy", vol. 1, 1949, pp. 1-5.
Metals Abstracts Annual Index, 1992, vol. 25, Part 1, 5-228, pp. 165-166.
Calka Andrzej
Ninham Barry W.
Williams James S.
Jenkins Daniel
The Australian National University
Walsh Donald P.
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