Powder metallurgy processes – Powder metallurgy processes with heating or sintering – Metal and nonmetal in final product
Patent
1990-08-23
1991-01-29
Lechert, Jr., Stephen J.
Powder metallurgy processes
Powder metallurgy processes with heating or sintering
Metal and nonmetal in final product
419 12, 419 13, 419 17, 419 19, 419 25, 419 28, 419 54, 419 55, 419 45, B22F 0000
Patent
active
049884808
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to the powder metallurgy, and more specifically, it deals with a method for making a composite material based on high-melting compounds of metals of group III-VI, VIII of the periodic table of the chemical elements.
BACKGROUND ART
The efficient use of composites in many fields of technology is due to a number of their valuable properties.
Such composites as, e.g. hard alloys exhibit a high hardness (86-94 HRA) in combination with high wear resistance, i.e. high resistance to wear in friction with both metals and nonmetals.
Another type of composites--carbide-containing steels-features a hardness which is close to that of cermets and a strength which is almost identical to that of steel.
Certain composites are capable to a large extent of retaining their properties at high temperatures.
It is most advantageous to use composites for the manufacture of cutting tools, dies and other products.
There are many diverse methods for making composites.
A most widely used method for making hard alloy materials (V. I. Tretiyakov "Fundamentals of Physical Metallurgy and Manufacturing Processes for Making Sintered Hard Alloys" (in Russian), 1976, Metallurgia Publishing House, Moscow, p.7), comprises preparing high-melting compounds with subsequent employment of powder metallurgy techniques comprising blending poweders of the resultant high-melting compounds with a binder metal, pressing compacts and sintering them at 1350.degree.-1550.degree. C. for several hours in vacuum or hydrogen electric furnaces.
High-melting compounds for hard alloys (carbides, borides, nitrides of transition metals) are produced by synthesis from respective metals (or their oxides) and nonmetals (boron, carbon, nitrogen) in electric furnaces at 1600.degree.-2200.degree. C. during several hours (ibid., pp. 265-293).
Another, more economically advanced and simpler method for making high-melting compounds (U.S. Pat. No. 3,726,643) comprises blending at least one metal selected from groups IV-VI of the periodic table of the chemical elements with at least nonmetal selected from carbon, nitrogen, boron, silicon, oxygen, phosphorus, fluorine, chlorine, and locally igniting the resultant mixture by any appropriate known method, e.g. using a tungsten filament. A temperature is thus provided which is necessary for initiating an exothermal reaction between metals and nonmetals in a small area of the mixture.
Further reaction of components of the mixture does not call for use of external energy supplies for heating and occurs on the account of heat of the exothermal reaction proper. The reaction propagates spontaneously through the mixture in the form of combustion due to heat transfer from a heated mixture layer to a cold layer at a combustion speed of 4 to 16 cm/s.
This method for making hard alloys is a multiple-stage process: it comprises a stage of preliminary preparation of high-melting compounds and their subsequent processing using known powder metallurgy techniques.
In addition, this method is associated with high power requirements and does not allow high-density homogeneous materials based on certain high-melting compounds such as TiB.sub.2 -based compounds to be produced because of their poor sintering capacity.
Known in the art is a method for making a hard alloy material (U.S. Pat. No. 4,431,448) having a porosity of less than 1% of the following composition in % by mass:
______________________________________ titanium diboride
40-60
binder 3-30
tatanium carbide
the balance,
______________________________________
comprising blending by mixing powders of titanium, boron, carbon and at
least one of metals of subgroup IB of the periodic table of the chemical
elements inactive with respect to boron or an alloy based on one of the
abovementioned metals or powders of metals forming said alloy under
exothermal reaction conditions. The mixture is then compacted and locally
ignited to initiate an exothermal reaction between titanium and boron and
carbon which then goes on spontaneously unde
REFERENCES:
patent: 4673550 (1987-06-01), Dallaire et al.
patent: 4778649 (1988-10-01), Niino et al.
patent: 4906295 (1990-03-01), Miyamoto et al.
patent: 4946643 (1990-08-01), Dunmead et al.
Borovinskaya Inna P.
Epishin Konstantin L.
Kvanin Vadim L.
Merzhanov Alexandr G.
Pitjulin Alexandr N.
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