Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
  • B24D3/00—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents
  • B24D3/02—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent
  • B24D3/04—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent and being essentially inorganic
  • B24D3/06—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent and being essentially inorganic metallic or mixture of metals with ceramic materials, e.g. hard metals, "cermets", cements
  • B24D3/08—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent and being essentially inorganic metallic or mixture of metals with ceramic materials, e.g. hard metals, "cermets", cements for close-grained structure, e.g. using metal with low melting point
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
  • C04B35/58—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides
  • C04B35/583—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on boron nitride
  • C04B35/5831—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on boron nitride based on cubic boron nitrides or Wurtzitic boron nitrides, including crystal structure transformation of 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
  • C22C32/0047—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
  • C22C32/0068—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 only nitrides

Definitions

• the method of converting hexagonal boron nitride (I-IBN) to cubic boron nitride (CBN) employing at least one catalyst selected from the class consisting of alkali metals, alkaline earth metals, lead, antimony, tin and nitrides of these metals is described in US. Pat. No. 2,947,617 Wentorf, Jr. This patent is incorporated by reference.
• minimum composition is that alloy composition for a given alloy system at which extensive solid solution is obtained at the lowest temperature.
• room temperature is intended to mean a temperature in the 7075F range. Quenching means instituting a rapid drop in temperature. With the apparatus employed herein a temperature drop of about l500C/minute can be achieved by simply turning of the power to the reaction vessel with the pressure still applied.
• This invention is an improvement over the invention in the Wentorf, Jr. et al. application.
• the product produced from the process of this invention is a solid abrasive transition metal-aluminum alloy matrix body consisting of small well-formed CBN crystals distributed uniformly through the metal binder phase. Conversion of HBN to CBN as high as 93 percent have been achieved.
• I-IBN dissolves quickly in a number of alloy systems made up of a small amount of aluminum together with at least two metals from the group consisting of chromium, manganese, iron cobalt and nickel; the alloy system becomes supersaturated with respect to CBN and the CBN precipitates; b.
• the operating temperature should be the lowest temperature at which all of the alloy will be melted 2 at the operating pressure whereby maximum liquid formation of the alloy will be made available, because yields of CBN appear to decrease with increasing temperature, and
• the specific composition of the transition metal alloy will be selected from the phase diagram for the alloy system. Otherwise, for convenience, the composition of the transition metal alloy is selected by choosing the binary or ternary eutectic or the minimum composition of the given alloy system. Once the specific combination has been selected, a small amount (less than 5 percent) of aluminum is added thereto.
• the aluminum can be added as aluminum metal, AlN or AI C
• the eutectic or minimum compositions for the given alloy system can be used, maximum liquid formation can be obtained at the lowest temperature and this, in turn, helps in maximizing the yield of CBN.
• the percentage of I-IBN converted to CBN is a function of the alloy, the pressure-temperature conditions and the initial amount of I-IBN.
• the metals listed hereinabove for the alloy formation are used, because they do not form such stable nitrides and borides as will reduce the availability of nitrogen and boron atom at the CBN-metal interface or significantly reduce (by dissolution) the amount of CBN.
• the method of this invention comprises the following steps:
• HBN powder with a powdered metallic phase to produce a homogeneous mixture, the atomic content of said metallic phase consisting essentially of aluminum atoms, atoms of a metal selected from the group consisting of chromium and manganese, and atoms of at least one metal selected from the group consisting of iron, cobalt and nickel, the weight percent of HBN in said mixture, being in the range of from about 10 to about 50 weight percent;
• the minimum pressure for the conversion of HBN to CBN has been found to be about 45-47 kb regardless of the specific metallic phase (unalloyed mix or preformed alloy) employed, but the minimum temperature varies.
• a metallic phase formulation it is preferable to determine the Pressure- Temperature Stability Region for CBN for that given formulation.
• a representative P-T phase diagram for boron nitride showing the CBN-stable and HBN-stable regions is shown in FIG. 1 of the Wentorf patent. Such a phase diagram is routinely determinable for a given metallic phase formulation by one skilled in the high temperature-high pressure art.
• the percentage yield of CBN increases sharply with increasing w/o of HBN in the mixture, reaches a peak and then falls off in a very steep drop in percent yield that was not expected and is not understood. In principle a continued increase or a leveling off in yield would have been expected. This peaking out and sharp decrease in CBN yield occurs in the -50 w/o I-IBN range regardless of the alloy solvent.
• Table 1 below shows the percent yield of CBN obtained as a function of increasing w/o of HBN in the mixture.
• the powders for yielding the alloy composition 46 w/o Fe, 32 w/o Ni, 21 w/o Cr and 1 We Al
• HBN powder were mixed and pressed into a cylindrical shape in a mold and were then subjected to temperatures in the 1440-l460C range and pressures in the 50-55 kb range. After lowering the temperature and pressure, a cylindrical abrasive body (CBN grains in an alloy binder) was removed from the reaction vessel remains. The metal was dissolved away in acid and the remaining CBN was weighed.
• Table [I shows changes occurring in CBN yield as the w/o HBN in the mixture was varied.
• powders were combined to yield the requisite alloy (39.2 w/o Ni, 58.8 w/o Mn and 2.0 w/o Al) in situ.
• Preparation and shaping of the mixture to be converted to the abrasive body and determination of CBN yield were as described above. The conversion was conducted at 52.5 kb and 1450C.
• Table V Data for Table V was obtained as described hereinabove.
• the metal alloy resulting from the powders was 39.2 w/o Fe, 58.8 w/o Mn and 2.0 w/o Al. Operating conditions were 52.5 kb and 1450C.
• the apparatus includes a pair of cemented tungsten carbide punches in opposed relationship to each other disposed on opposite sides of an intermediate belt or die member, and are aligned with a hole through the die member having tapered sides. The space between the punches and the wall of the hole accommodates a pair of gasket/insulating assemblies, which in turn surround a reaction vessel.
• the gasket/insulating assemblies are typically made of thermally insulating, electrically non-conducting pyrophyllite and include means by which electrical energy may be controllably applied to the system to provide the requisite heating of the reaction vessel.
• the reaction vessel parts to be employed in the conduct of this method should be made of sodium chloride, although other materials such as talc, potassium chloride, etc., as described in US. Pat. No. 3,030,662 Strong, incorporated by reference, may be employed. Techniques for calibration of the device for pressure and temperature are well established in the literature.
• the product of this process is a solid body recovered in some preselected form and consisting of small wellformed CBN crystals distributed uniformly through a metal binder phase.
• the volume percent of abrasive grain present therein may be readily made as high as about 55 percent by volume of the abrasive body.
• Some small amount of boron nitride remains in solution in the metallic phase accounting for the small differential between the l-lBN present in the original mixture and the amount of CBN recovered when the metal phase has been dissolved away to determine the CBN content.
• Abrasive bodies produced by the practice of this invention have been utilized to grind sapphire, silicon carbide, cemented tungsten carbide, steel and quartz.
• these abrasive bodies have also been formed as composites having a layer on one surface thereof of the solvent-binder alloy employed. This metal surface has been successfully brazed into a holder for mounting of the abrasive body for use in revolving machinery. Such composites may be advantageously brazed into saw blades and coring tools.
• the metal solvent-binder is acid soluble, the abrasive grain at the surface of the abrasive tool may be readily exposed by dipping the tool in a dilute acid solution.
• This method is particularly advantageous because the matrix for the completed tool serves as the solvent from which the CBN crystals appear to be precipitated.
• the HBN is rapidly soluble therein at the operating pressure/temperature conditions.
• This preparation of the CBN crystals by precipitation from a metallic solvent that remains as the binder promotes excellent metal-tograin contact (no weak intermediate phases) resulting in superior bonding between the binder and each abrasive crystal.
• the ability to use a number of transition metals for the conduct of the conversion of HBN to CBN enables the selection of many alloy systems from among the superalloys and stainless steels.
• Superalloy matrices in particular, provide very tough solventbinders for CBN grains.
• the amount of aluminum employed will preferably be less than 5 w/o in the aforementioned alloy systems and as such will not seriously affect the eutectic or minimum melting compositions for the systems.
• the minimum melting composition for the iron-nickelchromium-aluminum alloy system is about l3 l5C (at 1 atmosphere);
• the minimum melting composition for the nickel-chormium-aluminum system is about I345C (at l atmosphere)
• the minimum melting composition of the nickel-manganese-aluminum systern is about l0l0C (at l atmosphere).
• EXAMPLE l 0.282 gms of HBN and 0.396 gms of metal (58.8 w/o Mn, 39.2 w/o Ni and 2.0 w/o Al) were mixed and pressed into a pellet about 0.250 inch high X 0.250 inches diameter.
• HBN constituted about 42 w/o of the (metal plus HBN) mixture.
• a separate disc (0.060 inch deep) of metal alloy powder only was placed against the BN-metal pellet and both were simultaneously exposed to 52.5 kb and I450C for 30 minutes. CBN grains precipitated in the pellet and the metal alloy disc became firmly bonded together and bonded to the abrasive-containing portion.
• This metal alloy "pad” was silver-soldered to a steel cup having a :6 X l inch shaft attached thereto to produce an abrasive tool.
• the abrasive grains were exposed (i.e., the wheel was opened") by etching the surface for 3 minutes in aqua regia.
• This tool when mounted in a rotating machine such as a drill easily ground a steel file, a sapphire single crystal on both basal and prism planes, a SiC block, a piece of tungsten carbide, and a piece of talc.
• EXAMPLE 3 A mixture of metal and HBN and CBN was made and pressed into three separate cylinders about 0.25 inch in diameter.
• the mixture composition was 0.240 gms CBN 0.060 gms HBN 0.4824 gms Fe (46 W10) 0.336 gms Ni (32 w/o) 0.2208 gms Cr (21 w/o) 0.01053 gms Al (l w/o).
• the three pellets were placed (one above the other and in contact) in a high pressure cell and subjected to 55 kb and l450C for minutes. Upon removal from the cell the three pellets had sintered together and had cemented the CBN grains (both original and as precipitated) to form a single cylinder 0.262 inch high and about 0.250 inch in diameter. Metallographic examination of a polished section of this specimen shows good wetting of the CBN grains.
• EXAMPLE 4 Two grinding tools with a central hole to facilitate mounting were made simultaneously in a high pressure cell by treatment for 60 minutes at 52.5 kb and 1450C.
• Two discs 0.140 inch high X 0.250 inch in diameter were pressed from a powder mixture of HBN (0.140 gm), Mn(0.l70 gm), Fe(0.l14 gm) and Al(0.006 gm).
• a Vs inch diameter hole was then drilled through the center of each disc. 1n the high pressure cell these holes were filled with a vs inch diameter NaCl plug, and the two discs were separated by a 0.030 inch salt disc.
• Two doughnut-shaped grinding tools consisting of CBN in a metal matrix were produced. Using the central hole these tools could be mounted directly on a shaft without further preparation. In actual practice the initial discs could be pressed out in the final shape before the high pressure treatment rather than having to drill the central hole.
• EXAMPLE 5 The process of Example 4 was repeated except that the central hole was made 0.099 inch in diameter. Two annular grinding tools with sharp edges were simultaneously prepared. One such tool was taken as recovered from the high pressure-high temperature apparatus and was mounted on a shaft without additional preparation. The shaft was used to accommodate the tool in a small rotating machine and a piece of tool steel was ground easily therewith.
• the method of preparing cubic boron nitride abrasive tools comprising the steps of a. mixing HBN powder with a powdered metallic phase to produce a homogeneous mixture, the atomic content of said metallic phase consisting essentially of aluminum atoms, atoms of a metal selected from the group consisting of chromium and manganese, and atoms of at least one metal selected from the group consisting of iron, cobalt and nickel, the weight per cent of HBN in said mixture, being in the range of from about 10 to about 50 weight percent;
• the metallic phase consists of ironnickelchromium aluminum alloy containing 46 weight percent iron, 32 weight percent nickel, 21 weight percent chromium and 1.0 weight percent aluminum.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Structural Engineering (AREA)
• Crystallography & Structural Chemistry (AREA)
• Metallurgy (AREA)
• Polishing Bodies And Polishing Tools (AREA)
• Powder Metallurgy (AREA)
• Ceramic Products (AREA)

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Citations (4)

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• 1973
  • 1973-12-17 US US425201A patent/US3918931A/en not_active Expired - Lifetime
• 1974
  • 1974-11-12 ZA ZA00747256A patent/ZA747256B/xx unknown
  • 1974-12-02 GB GB52021/74A patent/GB1500709A/en not_active Expired
  • 1974-12-02 DE DE19742456888 patent/DE2456888A1/de not_active Withdrawn
  • 1974-12-03 NL NL7415736A patent/NL7415736A/xx not_active Application Discontinuation
  • 1974-12-09 CH CH1631474A patent/CH612115A5/xx not_active IP Right Cessation
  • 1974-12-10 JP JP14242574A patent/JPS5526695B2/ja not_active Expired
  • 1974-12-13 SE SE7415704A patent/SE7415704L/ not_active Application Discontinuation
  • 1974-12-16 IT IT30577/74A patent/IT1027699B/it active
  • 1974-12-16 CA CA216,292A patent/CA1066512A/en not_active Expired
  • 1974-12-17 BE BE151570A patent/BE823434A/xx not_active IP Right Cessation
  • 1974-12-17 AT AT1007874A patent/AT346201B/de not_active IP Right Cessation
  • 1974-12-17 FR FR7441453A patent/FR2254402B1/fr not_active Expired

Patent Citations (4)

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