Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/05—Mixtures of metal powder with non-metallic powder
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
  • C22C32/001—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides
  • C22C32/0015—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides with only single oxides as main non-metallic constituents
  • C22C32/0036—Matrix based on Al, Mg, Be or alloys thereof
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
  • C22C32/0047—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with carbides, nitrides, borides or silicides as the main non-metallic constituents
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
  • C22C32/0089—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with other, not previously mentioned inorganic compounds as the main non-metallic constituent, e.g. sulfides, glass

Definitions

• the invention relates to a process for producing sintered shaped bodies from an aluminum sintered mixture with an addition of wear-resistant powder particles, the sintered mixture being pressed to form a shaped body, heated to a sintering temperature below the melting point of aluminum and sintered under a protective gas atmosphere, and to a sintered shaped body made of an aluminum sinter mixture.
• Sintered moldings made of an aluminum-sinter mixture can not only be produced in large quantities with high manufacturing accuracy, but also have a comparatively low specific weight and good corrosion resistance.
• these advantages are offset by the disadvantage of low wear resistance.
• Hard coating by chemical deposition of, for example, titanium carbide, titanium nitride or a boride from the gas phase is, however, not expedient in the case of aluminum materials because the coating processes require reaction temperatures above the melting point of the aluminum.
• wear-resistant layers such as evaporation, ion implantation and. Like., Applied, so generally only thin, quickly removable layers are obtained.
• these methods are too expensive for coating cheap mass parts.
• at least when applying thicker layers the very good dimensional stability of the sintered shaped body is impaired.
• Another way of improving the wear resistance of sintered aluminum moldings is to incorporate more wear-resistant particles into the aluminum matrix.
• an additive made of more wear-resistant, intermetallic compounds for example a Mo-Co-Si alloy, which is pulverized by atomization, to the aluminum sintered mixture, but these proposals have not been successful in practice because the metallic additives react with the matrix material during sintering and brittle intermediate layers form under a comparatively strong sintering swelling. It is practically impossible to control the dimensional change during sintering. In addition, these brittle interlayers break when subjected to wear and the embedded particles crumble out. If you try to store particles in the aluminum matrix that do not react with the matrix and consist, for example, of aluminum oxide, they do not alloy, but they are only poorly integrated and can easily be torn out of the material in the event of wear.
• the invention is therefore based on the object of avoiding these deficiencies and of specifying a method by means of which dimensionally stable sintered shaped bodies can be obtained from an aluminum-sintered mixture with a comparatively high wear resistance.
• the invention achieves the object in that as a powdery additive, oxides, carbides, nitrides, borides or silicates of elements with a melting point above of aluminum are used which are less noble than the corresponding aluminum compound or aluminum with regard to the free enthalpy of reaction and form mixed crystals with the aluminum in the region of the sintering temperature.
• the aluminum of the matrix reduces the surface of the embedded particles.
• this reaction would cease very quickly if mixed crystals could not form which change the activities, so that even with a positive difference in the free enthalpy, such substances with the Aluminum can react.
• this reaction stops after reaching a comparatively low concentration of mixed crystals in the area of the phase interfaces because no more particles can be reduced due to the activity compensation.
• the adhesive layer formed consequently remains very thin because of the small amount converted and, moreover, acts as a diffusion barrier due to the high melting point, as a result of which a further reaction is effectively inhibited by diffusion.
• silicates predominates in the formation of mixed crystals between the aluminum and the silicate component of the silicate.
• silicates of metals which are less noble than aluminum in terms of their free enthalpy the silicate content is reduced, with thin adhesive layers being formed.
• the implementation is coming, however after reaching a certain layer thickness and after the incorporation of some formed aluminum oxide in the surface of the particles practically to a standstill, a further implementation is only possible through a diffusion of aluminum or silicon through the intermediate layer, which however strongly inhibits such diffusion.
• the very low reaction of the non-metallic additive particles with the aluminum matrix practically does not change the sintering behavior of the aluminum sintered mixture compared to the additive-free sintered mixtures. Consequently, the sintering conditions which are advantageous for the production of shaped sintered bodies without wear-reducing additives can also be used for the sintering of the aluminum sintered mixtures with such wear-reducing, non-metallic additives.
• the particles of the powdery additive should have a spherical shape with a grain diameter between 30 and 100 ⁇ m. If the grain diameter is below the specified range, there is no noticeable improvement in wear resistance because the wear-resistant additional particles can be pressed into the matrix structure during wear. In addition, too small a grain size leads to a loss of strength of the shaped bodies. A large number of very fine additional particles hinder the formation of the sinter bridges that determine the strength of the material. If the grain size exceeds a certain dimension, there is a risk that the additional particles will be torn out of the structure. In addition, difficulties can arise with regard to the different thermal expansion coefficients of the non-metallic inclusions and the aluminum matrix.
• the grain diameter of the powdery non-metallic additive is between 50 and 200 ⁇ m lies. Additional particles with a spherical shape ensure better mechanical properties of the sintered molding, in particular a better elongation at break can be achieved. In addition, the green bodies are more compressible and the tool wear when pressing the green bodies is less.
• the content of additional particles should make up at least 0.5% by volume of the sintered mixture. If the powdery additive content rises above 50% by volume, the strength of the sintered materials is impaired. In general, an addition of 1 to 30% by volume of non-metallic substances to the aluminum sintering mixture will ensure the best results.
• the hardness of the non-metallic additives only plays a subordinate role for the wear properties of the sintered molded body, because all the non-metallic substances in question have a sufficiently high hardness.
• the advantages of conventional aluminum sintered shaped bodies can be combined with the advantage of a considerable improvement in wear behavior.
• the adhesive layers that form between the embedded, wear-resistant particles and the matrix are limited in terms of the layer thickness to 0.01 to 1.0 pm, so that, despite the brittle intermetallic phases, ductile behavior is achieved which allows the wear-resistant particles to be incorporated well into the matrix ensures that the material is also subjected to greater wear.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Powder Metallurgy (AREA)
• Compositions Of Oxide Ceramics (AREA)

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Citations (5)

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• 1986
  • 1986-07-24 AT AT86890217T patent/ATE59064T1/de not_active IP Right Cessation
  • 1986-07-24 DE DE8686890217T patent/DE3676131D1/de not_active Expired - Lifetime
  • 1986-07-24 EP EP86890217A patent/EP0213113B1/fr not_active Expired - Lifetime

Patent Citations (5)

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