Powder metallurgy processes – Powder metallurgy processes with heating or sintering – Metal and nonmetal in final product
Patent
1990-08-23
1991-10-01
Lechert, Jr., Stephen J.
Powder metallurgy processes
Powder metallurgy processes with heating or sintering
Metal and nonmetal in final product
419 12, 419 17, 419 28, 419 45, 419 48, B22F 324
Patent
active
050531921
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to the powder metallurgy and, in particular, it deals with a method and apparatus for making products from powdered materials.
BACKGROUND OF THE INVENTION
Known in the art is a method for making products from powdered heat-resistant materials by hot impact extrusion, comprising preparing cylindrical compacts by using conventional techniques of powder metallurgy, hydrostatic pressing of compacts under a pressure of 150 to 460 MN/m.sup.2, sintering them in vacuum at up to 1450.degree. C. during 1 to 6 hours, and subjecting the compacts to hot dynamic extrusion with glass lubricant, with subsequent annealing in vacuum during one hour (Abstr. Jr. "Metallurgia", 1981, 1.GAMMA.445; City of London Polytechnic, Dep. of Metallurgy and Materials. Ill. 12; Table ; ref. 9. "Hot Impact Extrusion and Subsequent Treatment of Some High-Temperature Nickel Alloys"). The dynamic extrusion allows high-temperature nickel-based alloys containing less than 50% of a high-melting component to be processed, and in certain applications it is capable of hot hardness, lowering porosity and distribution of particles in the material.
The main disadvantages of this method are due to its multiple-stage implementation which results in a substantial energy consumption, the need to use sophisticated production equipment, long process time and high labour effort. In addition, it is known that sophisticated alloys containing more than 50% of a high-melting component are not suitable for dynamic extrusion because of high hot and hardness.
Known in the art is a method for making products from hard alloy composite comprising carrying out a combustion reaction in a mixture of starting powders (metal, nonmetal and binder), with subsequent deformation of the mixture by three-dimensional compression ("New Methods for Making High-Temperature Materials Based on Combustion". Merzhanov A. G., Borovinskaya I. P., Yukhvid V. I., Ratnikov V. I. in the book "Scientific Fundamentals of Materials Technology" (in Russian). Moscow, Nauka Publishing House, 1981. pp. 193-206). This method can be regarded as a modification of hot pressing in which the combustion process prepares components for deformation of the material synthesis and heating). This method was used for making a tungsten-free hard alloy from elements (Ti, C, Ni, Mo). The mixture is blended for obtaining industrial alloys (titanium carbide with 20 and 30% of nickel and molybdenum binder). Materials with rather good properties close to commercially applicable grades can be produced under certain conditions. The method of self-propagating high-temperature synthesis under compression is used nowadays also for producing compact material from individual high-melting compounds.
The abovementioned method makes it possible to produce hard-alloy materials and products in a single stage during a short time period (about one munite) with minimum energy consumption.
The main disadvantage of the method is the limitation of configuration of products so that elongated products, i.e. products having a large length-to-diameter ratio (h/d>>1) are produced. The non-uniform three-dimensional compression pattern used in this method results in mainly compressive stresses being built up in the material. For this reason, if products with h/d>1 are made by this method, they loose the initial shape with fracturing and underpressing.
Known in the art is a method of self-combustion sintering of ceramics under pressure, comprising propagation of exothermal synthesis reaction under a high pressure, wherein the synthesis and compaction of the sintered material are carried out in a blended powdery mixture containing elements necessary for the synthesis (Miyamoto K., Kamija H., Koizumi M. "High-Pressure Self-Combustion Sintering of Ceramics." Funtai oyobi Funmatsu Jaken. 1987, vol. 34. No. 3. pp. 101-196 (JP) CA 107 No 1. p. 266 (119811H). Abstr Jr. Khimia 1988, vol. 13, p. 11, 7E, 13M).
In this method, heat released as a result of the synthesis reaction is the source of energy for
REFERENCES:
patent: 4673550 (1987-08-01), Dallaire et al.
patent: 4746363 (1988-05-01), DeAngelis
Buchatsky Leonid M.
Merzhanov Alexandr G.
Podlesov Vadim V.
Shishkina Tatyana N.
Stolin Alexandr M.
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