EP0484014A1 - Compositions métallo-céramiques de carbure de bore-métal réactif ayant une microstructure créée par un traitement thermique après densification - Google Patents

Compositions métallo-céramiques de carbure de bore-métal réactif ayant une microstructure créée par un traitement thermique après densification Download PDF

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Publication number
EP0484014A1
EP0484014A1 EP91309628A EP91309628A EP0484014A1 EP 0484014 A1 EP0484014 A1 EP 0484014A1 EP 91309628 A EP91309628 A EP 91309628A EP 91309628 A EP91309628 A EP 91309628A EP 0484014 A1 EP0484014 A1 EP 0484014A1
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Prior art keywords
reactive metal
boron carbide
phase
aluminum
metal
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EP91309628A
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German (de)
English (en)
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Aleksander J. Pyzik
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Dow Chemical Co
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Dow Chemical Co
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    • 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
    • C22C1/058—Mixtures of metal powder with non-metallic powder by reaction sintering (i.e. gasless reaction starting from a mixture of solid metal compounds)
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
    • C22C29/02—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides
    • C22C29/06—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds
    • C22C29/062—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds based on B4C

Definitions

  • This invention concerns ceramic-metal composites, also known as cermets, based upon boron carbide and a source of a metal which reacts with boron carbide.
  • Cermets have properties that differ from those of either the ceramic phase or the metal phase alone. They are conventionally made by powder metallurgical methods, that is, by preparing and mixing individual metal and ceramic powders, pressing the mixed powders into a required shape and subjecting the shape to a sintering heat treatment to bond the particles and develop the required structural integrity, often by direct ceramic-to-ceramic bonding.
  • Cermets are conventionally used to make engineering components, such as parts of gas turbine or diesel engines, that require mechanical property stability when exposed to rapid temperature changes, strength at operating temperatures and creep resistance. They tend to be less brittle and less prone to formation of extended defects within the material than conventional ceramics.
  • U.S. Patent 4,556,424 discloses a method of improving the fracture toughness of a hard metal or metal-bound ceramic by exposing it to a heat treating process similar to the transformation toughening of steel.
  • a ceramic composite such as cobalt-bound tungsten carbide, is first cooled to transform the binder material from a first state to a second state and cause deformation of the binder material.
  • the composite is then heated above ambient temperature to cause the binder material to revert to its first state while retaining some measure of the deformation.
  • the heated composite material is then quenched or subjected to rapid cooling.
  • U.S. Patent Nos. 4,702,770 and 4,718,941 teach heat treating ceramic precursors infiltrated with a molten metal to tailor the microstructure of boron carbide-reactive metal cermets.
  • Figure 1 illustrates the post-densification heat treatment of boron carbide containing varying amounts of aluminum at varying temperatures.
  • Figure 2 illustrates post-densification heat treatment of a boron carbide composite containing 30% by volume aluminum showing hardness as a function of heat treatment time and temperature.
  • Figure 3 provides curves showing the effect of heat treatment time on fracture toughness of a boron carbide-aluminum composite which has been subjected to a post-densification heat treatment.
  • One aspect of the present invention is a boron carbide-aluminum cermet characterized by a boron carbide phase, an aluminum phase and an AlB2 phase or an Al4BC phase or an AlB2 phase and an Al4BC phase.
  • a second aspect of the present invention is a boron carbide-reactive metal cermet characterized by a boron carbide phase, a reactive metal phase and a reactive metal boride phase, or a reactive metal boron carbide phase or a reactive metal boride phase and a reactive metal boron carbide phase, the reactive metal being arsenic, barium, beryllium, calcium, cobalt, chromium, iron, hafnium, iridium, lanthanum, lithium, magnesium, manganese, molybdenum, sodium, niobium, nickel, osmium, palladium, platinum, plutonium, rhenium, rhodium, ruthenium, scandium, silicon, strontium, tantalum, technetium, thorium, titanium, uranium, vanadium, tungsten, yttrium or zirconium.
  • a third aspect is a process for preparing a boron carbide-aluminum cermet comprising:
  • a fourth aspect is a process for preparing a boron carbide-reactive metal cermet comprising:
  • Powder metallurgy procedures are preferred for preparing densified composites suitable for heat treatment.
  • Powder mixtures may be densified as is, placed in a container before densification or converted to a preform, by a known procedure such as cold pressing, cold isostatic pressing or cold isostatic pressing before densification.
  • the powder mixtures usually contain from 20 to 60 percent by volume of a reactive metal such as aluminum prior to densification. After a post-densification heat treatment, the proportion of metal is from 2 to 12% by volume.
  • the post-densification heat treatment produces a microstructure containing, in addition to the boron carbide and reactive metal phases, a metal boride phase such as AlB2, or a metal boron carbide phase such as Al4BC or a metal boride phase and a metal boron carbide phase.
  • a metal boride phase such as AlB2
  • a metal boron carbide phase such as Al4BC
  • a metal boride phase and a metal boron carbide phase a metal boron carbide phase
  • the aluminum phase of boron carbide-aluminum cermets may be formed from aluminum metal, aluminum metal alloys or aluminum compounds that are reduced totheir corresponding metal during densification.
  • Boron carbide-aluminum cermets have a number of potential applications or end uses. The applications include, but are not limited to, lightweight structures, cutting tools, spent nuclear fuel containers, radiation resistant structures, hot and cool parts of turbine engines, impact resistant structures, abrasive and wear resistant materials, semiconducting devices, and structures requiring increased thermal shock resistance and a high degree of chemical stability.
  • Metals that react with boron carbide to form similar boron carbide-reactive metal cermets include arsenic, barium, beryllium, calcium, cobalt, chromium, iron, hafnium, iridium, lanthanum, lithium, magnesium, manganese, molybdenum, sodium, niobium, nickel, osmium, palladium, platinum, plutonium, rhenium, rhodium, ruthenium, scandium, silicon, strontium, tantalum, technetium, thorium, titanium, uranium, vanadium, tungsten, yttrium or zirconium.
  • the reactive metal phase may be formed from a reactive metal, a metal alloy containing the reactive metal or a reactive metal compound that reduces to its corresponding metal or metal alloy during densification.
  • the cermets of the present invention result from a process which differs from prior art processes in two aspects.
  • Densification of :he admixture of boron carbide and the source of aluminum or another reactive metal occurs at a temperature in the vicinity of the melting temperature of the metal. This temperature is believed to minimize the reaction between boron carbide and the aluminum or other reactive metal during densification.
  • the densified admixture or cermet undergoes a heat treatment to produce a microstructure that includes one or more phases other than the boron carbide phase and the reactive metal phase. Variations in the microstructure lead to improvements in physical properties such as fracture toughness or impact strength.
  • Post-densification heat treatment occurs at a temperature within a range of 450°C to 1000°C.
  • the range is desirably from 500°C to 800°C and preferably from 600°C to 700°C.
  • Heat treatment times fall within a range of from one to 50 hours.
  • the treatment time range is desirably from 1 to 30 hours and preferably from 10 to 20 hours.
  • Heat treatment temperatures within a range of 600°C to 700°C lead to formation of a reactive metal boride, such as, AlB2.
  • the boride enhances impact resistance over that of the densified composite prior to heat treatment.
  • a reactive metal boron carbide such as, Al4BC begins to form.
  • the amount of the reactive metal boron carbide relative to the reactive metal boride also increases.
  • the reactive metal boron carbide is the dominant reaction product.
  • Heat treatment temperatures in excess of 1000°C cause the reactive metal boride to decompose and generate free reactive metal. Mixtures of the reactive metal boride and the reactive metal boron carbide have fracture toughness and hardness values greater than that of the densified composite prior to heat treatment.
  • the boron carbide was a powder with 21.27% total carbon content, 0.4% free carbon, 1.27% oxygen and a surface area of 6.8 m2/g.
  • the major impurities were 161 ppm Ca, 142 ppm Cr, 268 ppm Fe and 331 ppm Ni.
  • the aluminum powder, Alcan 105 produced by Alcan-Toyo America, Inc. contained 0.8% Al2O3, 0.18% Fe and 0.12% Si and had a surface area of 0.5m2/g.
  • a mixture of 70R% by volume boron carbide powder and 30% by volume aluminum powder was mixed and pressed into 24 mm diameter pellets.
  • the pellets were heat-treated for one hour in a mullite tube furnace, in flowing argon, at a temperature within a range of 400°C to 1200°C.
  • the heat-treated pellets were cooled to room temperature either at a rate of 10/minute or by quenching into liquid nitrogen.
  • Crystalline phases were identified by x-ray diffraction with a Phillips diffractometer using CuK radiation and a scan rate of 2° per minute. The chemistry of all phases was determined from electron probe analysis of polished cross-sections using a CAMECA CAMEBAX electron probe. The accuracy in the determination of elemental composition was better than 3% of the amount present.
  • the area of the aluminum melting endotherm in the high temperature DSC scan was used as a measure of the reactivity between B4C and Al at temperatures between 550°C and 1200°C.
  • the data were collected using a Perkin-Elmer DTA 1700 interfaced to a computer.
  • the purge gas was ultra high purity argon flowing at 40 cc/min.
  • the samples were heated in alumina crucibles at 20°C/min and high purity aluminum (99.999%) was used as a standard.
  • the percent aluminum metal was given by A/B x 100, where A is the peak area in cal/g of the Al melt endotherm in the sample and B is the same for the Al standard. Precision and accuracy were 2 percent.
  • AlB2 and Al4BC are present and, as temperature increases, the relative amount of Al4BC increases. Between 900°C and 1000°C, the dominant reaction product is Al4BC. At temperatures above 1000°C, AlB2 decomposes and generates free aluminum. Heat treatment above 1000°C produces mainly AlB24C4 and some Al4C3. Phases formed below 1000°C are aluminum rich and their formation leads to the rapid depletion of the metal. Phases formed above 1000°C are boron and carbon rich resulting in B4C depletion and development composites with larger amounts of free metal and smaller amounts of boron carbide than the same starting powders heated below 1000°C.
  • the major phases influencing the mechanical properties of B4C/Al based materials are Al4BC, AlB2, AlB24C4 and Al4C3. Because the formation of AlB24C4 is associated with the existence of undesirable Al4C3, the heat treatment should be limited to temperatures of 1000°C or lower where AlB2 and Al4BC are the predominant new phases.
  • Example 2 illustrates that hardness of B4C/Al cermets can be changed as a function of phase chemistry.
  • Example 1 The same powders were used as in Example 1.
  • the boron carbide and aluminum powders were dry mixed in a rotary blender and then pressed into 75 mm diameter discs using uniaxial compaction in a stainless steel die. No lubricants or binders were used.
  • the samples were placed into metal cans.
  • the sealed cans were placed in fluid dies.
  • the fluid dies with mixed B4C and Al powders were heated in the furnace of Example 1 to 640°C.
  • the fluid dies were then removed from the furnace, placed in a forging press, and compacted.
  • the compacted dies were removed from the forging press and cooled to room temperature.
  • the discs were separated from the cooled dies using conventional procedures and cut into various shapes for testing and characterization.
  • the bulk hardness was measured on surfaces polished successively with 45, 30, 16, 6 and 1 um diamond paste and finally finished using colloidal silica suspension on a LECO automatic polisher.
  • the Rockwell A hardness was measured using a 13.3 kg load.
  • the Vickers microhardness of isolated phases was measured using a LECO tester and loads of 10 to 20 grams. The largest grains of a particular phase were examined in order to eliminate or minimize the contribution from adjacent or underlying material. Generally, the distance from the center of the indent to the nearest grain boundary was over twice the indent diagonal dimension. The indent diagonals were measured using a scanning electron microscope at 10000X.
  • the B4C/30% by volume Al material had a hardness of 81 in Rockwell A scale.
  • Post-densification heat treatment at 600°C and 1000°C provided a maximum hardness value of 83, which remained stable for extended times as shown in Figure 2.
  • the hardness declined initially due to the decomposition of AlB2, but then increased again as Al4BC was formed.
  • Heat treatments conducted at 700°C, 800°C, 900°C and 1100°C produced a maximum in the hardness versus time curve. At higher temperatures, less time was required to obtain maximum hardness.
  • the change in hardness is characteristic of the B4C/Al system and due to the kinetics and B-C-Al phase equilibrium. Below 1000°C, in the initial stage of heat treatment, hard Al4BC is favored. With increased time, there is insufficient aluminum available and softer AlB2 forms decreasing overall hardness. Between 600°C and 1000°C Al4BC and AlB2 are both present. Increases in the AlB2/Al4BC ratio lower the maximum hardness and make the transition from rising to declining hardness more gradual.
  • Example 3 illustrates that fracture toughness of dense B4C/Al material can be increased. This increase is associated with densification of the metal phase. While the formation of ceramic phases reduces toughness, the extent of this reduction depends on the type of phase formed. AlB2 is the least detrimental.
  • Fracture toughness was measured using the Chevron notch technique and standard 4 x 3 x 45 mm samples.
  • the notch was produced with 250 um wide diamond blade and the notch depth to sample height ratio was 0.42.
  • a cross head speed of 0.05mm/minute was used in a 3 point bend fixture. The average of 5 to 7 measurements was reported.
  • Example 4 shows that post-densification heat treatment can be used to improve many properties of B4C/Al cermets by changing the cermet into a multi-phase ceramic material containing only a small amount of residual metal.
  • the AlB2/Al4BC ratio can be changed and controlled by heat treatment at a temperature between 700°C and 900°C, the properties of B4C/Al composites canbe selected for a specific application. Processing at 1000°C or below allows the formation of large amounts of AlB2 and avoids the formation of Al4C3.
  • the resultant B4C/Al cermets are characterized by a microstructure of isolated boron carbide grains in an aluminum matrix with improved fracture toughness and fracture strength.

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
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  • Manufacture Of Alloys Or Alloy Compounds (AREA)
EP91309628A 1990-11-02 1991-10-18 Compositions métallo-céramiques de carbure de bore-métal réactif ayant une microstructure créée par un traitement thermique après densification Withdrawn EP0484014A1 (fr)

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EP (1) EP0484014A1 (fr)
JP (1) JPH055150A (fr)
CA (1) CA2054834A1 (fr)
FI (1) FI915158A (fr)
IL (1) IL99944A0 (fr)
NO (1) NO914293L (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996018748A2 (fr) * 1994-12-12 1996-06-20 The Dow Chemical Company Substrat pour disque informatique, procede de fabrication dudit disque et articles ainsi produits
WO1996018749A2 (fr) * 1994-12-12 1996-06-20 The Dow Chemical Company Composants d'unite de disque dur et procedes de fabrication desdits composants
US20130344316A1 (en) * 2011-03-08 2013-12-26 Senad Hasanovic Composite Material Comprising a Precious Metal, Manufacturing Process and Use of Such Material
CN110603340A (zh) * 2017-05-11 2019-12-20 瑞典海博恩材料与技术有限公司 用于核屏蔽应用的硼碳化铁钨体
CN115198211A (zh) * 2022-07-05 2022-10-18 贵州航天天马机电科技有限公司 一种TiCx-Cu金属陶瓷的增韧方法

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4605440A (en) * 1985-05-06 1986-08-12 The United States Of America As Represented By The United States Department Of Energy Boron-carbide-aluminum and boron-carbide-reactive metal cermets
WO1987000557A2 (fr) * 1985-07-26 1987-01-29 Washington Research Foundation Composite de carbure de bore-aluminium d'utilisation generale et sa production par regulation de la microstructure
EP0250210A2 (fr) * 1986-06-17 1987-12-23 The Regents Of The University Of California Procédé de fabrication de matériaux composites métallo-céramiques et matériaux composites ainsi obtenus
EP0378504A1 (fr) * 1989-01-13 1990-07-18 Lanxide Technology Company, Lp. Procédé pour la préparation de corps autoporteurs à porosité contrôlée et à propriétés graduelles, et corps ainsi obtenus

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4605440A (en) * 1985-05-06 1986-08-12 The United States Of America As Represented By The United States Department Of Energy Boron-carbide-aluminum and boron-carbide-reactive metal cermets
WO1987000557A2 (fr) * 1985-07-26 1987-01-29 Washington Research Foundation Composite de carbure de bore-aluminium d'utilisation generale et sa production par regulation de la microstructure
EP0250210A2 (fr) * 1986-06-17 1987-12-23 The Regents Of The University Of California Procédé de fabrication de matériaux composites métallo-céramiques et matériaux composites ainsi obtenus
EP0378504A1 (fr) * 1989-01-13 1990-07-18 Lanxide Technology Company, Lp. Procédé pour la préparation de corps autoporteurs à porosité contrôlée et à propriétés graduelles, et corps ainsi obtenus

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1996018748A2 (fr) * 1994-12-12 1996-06-20 The Dow Chemical Company Substrat pour disque informatique, procede de fabrication dudit disque et articles ainsi produits
WO1996018749A2 (fr) * 1994-12-12 1996-06-20 The Dow Chemical Company Composants d'unite de disque dur et procedes de fabrication desdits composants
WO1996018748A3 (fr) * 1994-12-12 1996-08-15 Dow Chemical Co Substrat pour disque informatique, procede de fabrication dudit disque et articles ainsi produits
WO1996018749A3 (fr) * 1994-12-12 1996-08-22 Dow Chemical Co Composants d'unite de disque dur et procedes de fabrication desdits composants
US20130344316A1 (en) * 2011-03-08 2013-12-26 Senad Hasanovic Composite Material Comprising a Precious Metal, Manufacturing Process and Use of Such Material
US9096917B2 (en) * 2011-03-08 2015-08-04 Hublot Sa, Genève Composite material comprising a precious metal, manufacturing process and use of such material
CN110603340A (zh) * 2017-05-11 2019-12-20 瑞典海博恩材料与技术有限公司 用于核屏蔽应用的硼碳化铁钨体
US11279991B2 (en) 2017-05-11 2022-03-22 Hyperion Materials & Technologies (Sweden) Ab Iron tungsten borocarbide body for nuclear shielding applications
CN115198211A (zh) * 2022-07-05 2022-10-18 贵州航天天马机电科技有限公司 一种TiCx-Cu金属陶瓷的增韧方法

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NO914293D0 (no) 1991-11-01
FI915158A0 (fi) 1991-11-01
FI915158A (fi) 1992-05-03
JPH055150A (ja) 1993-01-14
CA2054834A1 (fr) 1992-05-03
NO914293L (no) 1992-05-04
IL99944A0 (en) 1992-08-18

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