Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/22—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip
  • B22F3/225—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip by injection molding
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/10—Sintering only
  • B22F3/1017—Multiple heating or additional steps
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/12—Both compacting and sintering
  • B22F3/14—Both compacting and sintering simultaneously
  • B22F3/15—Hot isostatic pressing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/22—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy

Definitions

• the invention relates to a method and a device for producing molded parts from alloy material, in particular from nickel-based alloys, chromium-based alloys, titanium-based alloys, and dispersion-hardened alloys.
• Moldings are usually made from nickel-based alloys, chrome and titanium alloys by investment casting. Castings, however, have comparatively poor mechanical properties, in particular with regard to the fatigue strength, which is the case with statically or dynamically stressed parts, e.g. B. in rotor blades and vanes of turbines, is important.
• the object of the invention is to provide a method and a device for producing molded parts of the type mentioned at the outset, in which the aforementioned disadvantages of wrought alloys or cast alloys are overcome and, in particular, improved properties are achieved with simple effort.
• the object on which the invention is based is achieved in a method according to the invention in that a powder of the corresponding alloy or a mixture of powders of the corresponding alloy components with the aid of plastics in the form of thermoplastics, thermosets and lubricants to form an injectable approx. 30 to 50 volume percent Plastic-containing granulate mass is processed, which is injection molded into a molded part.
• the injectable granulate mass is prepared in particular by dissolving the plastics in a solvent which does not attack the base metal of the alloy and mixing them with the metal powder, and then evaporating the solvent.
• the plastics of the injection molded part are expediently removed from the molded part at least by heat treatment up to approximately 600 ° C. under protective gas or vacuum. partially removed.
• the molded part is advantageously sintered under protective gas at a temperature of 50 to 90% of the melting temperature of the metal used in the alloy. This causes the molded part to shrink, reaching a density of 95 to 98% of the theoretical density.
• the injection molded part can be hot isostatically compressed at a pressure of approximately 500 to 3000 bar and at the sintering temperature of the metal used. This brings the density of the molded part to almost 100%, which increases the strength considerably.
• Polyethylene, polystyrene, polyamides and / or cellulose and their derivatives are advantageously suitable as thermoplastics, epoxy resins, phenolic resins and / or polyimides as thermosets, while stearic acid, stearates and / or waxes are advantageously used as plastic lubricants.
• a low-carbon starting powder or mixture For molded parts made of a nickel-based alloy, a titanium-based alloy or a chrome-based alloy tion are constructed, it is advantageous to use a low-carbon starting powder or mixture. Most binders leave behind free carbon when burned out, which could impair the properties of the molded part. By using a low-carbon starting material, the maximum permissible carbon content in the molded part is not exceeded, despite the carbon remaining from the binders.
• the aforementioned problem is also overcome if a heat treatment is carried out under hydrogen after the burnout.
• the set pressure is 1 to 300 bar, the heat treatment takes place at a temperature of approx. 400 to 1000 ° C.
• the method according to the invention can be modified in such a way that a heat treatment is carried out after the sintering process in order to set the most favorable grain size of the material of the molded part.
• a device for carrying out the method according to the invention is characterized in that those parts of the device which experience wear due to friction with the injectable granulate mass are formed or coated from the material of the alloy to be processed. This prevents contamination during processing of the alloy used.
• the vibration resistance of the material is improved by the invention. It can also advantageously produce complicated parts with high demands on the end profile, such as. B. turbine blades and vanes or integral turbine wheels.
• the finished molded part is in a form that may require a subsequent machining or electrochemical processing to a small extent.
• the drastic reduction in the machining effort compared to the known manufacturing processes for molded parts mentioned in the introduction creates a simple manufacturing process with a high-quality result, which is very inexpensive in comparison with known processes.
• the plastics used are dissolved in a solvent that does not attack the metals and mixed with the metal powder.
• the solvent is then removed vapors, and the mass is processed into an injectable granulate. These granules can now be processed into molded parts by injection molding.
• the plastic is removed from the molded part after injection molding by heat treatment up to 600 ° C under protective gas.
• the part is then sintered, the sintering process taking place under a protective gas or vacuum at temperatures of 50 to 90% of the melting temperature of the metal used.
• the part shrinks linearly between 10 and 25% and reaches a final density of 95 to 98% of the theoretical density of the material.
• nickel-based alloys The main problem with nickel-based alloys is that most binders leave free carbon when burned out. This can impair the properties of the molded part to be manufactured.
• the binder releases hydrogen when it burns out. Hydrogen is readily soluble in titanium alloys and worsens the strength properties. The hydrogen must be removed by heat treatment using known methods in vacuo or under a protective gas.
• Titanium alloys can be oxidized very easily. All process steps that take place at a temperature higher than room temperature should therefore be carried out in a vacuum or under protective gas. This includes, in particular, mixing the mass and spraying the molded parts. Known evacuable mixers are advantageously used. Evacuable injection molding machines are expediently used for spraying.
• Chromium alloys are very similar to nickel alloys in terms of their chemical properties, which is why the problem is the same. Remedies can be used to overcome the problem of free oxygen, as stated under Ni-based alloys.
• Dispersion hardened alloys are two or multi-phase materials in which the matrix consists of an oxidation-resistant, usually single-phase alloy. Particles of a second phase (or more phases) are embedded in the matrix.
• the characteristic of dispersion-hardened alloys is that the particles cannot be dissolved in the matrix. The particles cause the material to harden.
• the advantage of the dispersion-hardened alloy is its aging Resistance at high temperature due to the insolubility of the second phase.
• the particles are usually introduced into the melt of the matrix alloy. This method has the disadvantage that concentration gradients occur when the molded parts are poured because of the density differences between the matrix and the particles. Adhesive forces also tend to clump the particles. Overall, only a very unsatisfactory particle distribution can be achieved. A homogenization by plastic forming is not possible, since the plastic deformability is not sufficient with the known alloys.
• Very homogeneous particle distributions can be produced in the method according to the invention.
• the particles are added to the matrix powder and mixed with it. Since there is no melting phase during the entire process, segregation or gradient formation is not possible. Even with the steps "preparation of the mass and injection molding" the distribution is not deteriorated, but rather improved.
• the very homogeneous particle distribution that can be achieved results in considerably better strength properties of the molded parts than in known manufacturing processes.
• the core consists of a material that also decomposes when it burns out (core materials: plastics, preferably thermosets, possibly reinforced with C fibers). With the help of cores z. B. Easily produce complicated cooling configurations in turbine blades.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Mechanical Engineering (AREA)
• Powder Metallurgy (AREA)

Applications Claiming Priority (2)

Publications (2)

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Cited By (12)

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Citations (7)

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• 1981
  • 1981-05-22 DE DE3120501A patent/DE3120501C2/de not_active Expired
• 1982
  • 1982-05-03 US US06/373,827 patent/US4478790A/en not_active Expired - Fee Related
  • 1982-05-12 EP EP82104097A patent/EP0065702A3/fr not_active Withdrawn
  • 1982-05-19 JP JP57085647A patent/JPS57198202A/ja active Pending

Patent Citations (7)

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