Classifications

• • 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
• • 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
  • C22C32/0052—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 carbides
  • C22C32/0057—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 carbides based on B4C

Definitions

• the invention relates to moldings with high hardness and high toughness for the processing of metals, hard metals, ceramics and glasses made of sintered boron carbide and a binder metal phase.
• Boron carbide is particularly resistant to sandblasting. This opens up certain possible uses for sintered bodies containing boron carbide, although the low breaking strength of the sintered bodies must be taken into account.
• the wear value of a sintered body with 95% by weight of boron carbide (20% by weight of C) and 5% by weight of Fe compared to the wear values of sintered bodies made of W C -Co or TiC-Fe-Cr or TiC-VC-Fe-Ni the lowest (RKKieffer, P.Schwarzkopf "Hartscher und Hartmetalle", Springer-Verlag 1953, pages 524 and 525). Elsewhere in this document (page 327) it is mentioned that attempts to set boron carbide with tough metals have failed.
• B 4 C particles are sintered with powder of the known binding metals cobalt or nickel, undesirable chemical reactions and the formation of further phases, for example borides, occur. As a result, due to the different properties of the phases that are already present and those that are forming, cracks and gaps can already form in the shaped body during cooling.
• the invention had for its object to present molded articles made of B 4 C, in which the strength, in particular the Toughness compared to moldings made of pure B 4 C is increased and which are particularly suitable for cutting or grinding tools or for applications in which mechanical wear loads or high surface pressures have to be countered, such as, for example, in the case of nozzles.
• the object of the invention is also to provide a simple method for producing such molded articles.
• the method according to the invention is intended to be able to produce cutting platelets for machining or other moldings for tools for grinding, honing, rubbing, etc. of metals, in particular non-ferrous metals, hard metals, ceramics and glasses.
• the carbon doping of the B 4 C can be in the range between 0% by weight and 2.0% by weight of the shaped body weight.
• the binder metal phase content is in the range between 10 and 15% by volume of the shaped body volume.
• Mo and W belong to the metals with low heat of formation of both metal borides and carbides.
• the B 4 C is doped with carbon.
• 0.1 to 2.0% by weight of activated carbon, based on the product weight, is homogeneously mixed into the powder mixture from step a) before step b).
• the compact can be heated to the sintering temperature and then introduced into the die. The final compact can be ejected hot from the die and then cooled.
• the sintering temperature is with carbon doping near the upper range value.
• the hot pressing of Mo and B 4 C powders takes place at temperatures at which both materials are compressed but no molten phase occurs yet.
• the essence of the method according to the invention is the comparatively rapid execution of the hot pressing, in which even a very small proportion of the metal powder in the powder mixture is retained as the metallic phase in the molded product and embeds the B 4 C particles.
• Molded articles were produced: with 5% by volume Mo (corresponds to 20% by weight) and 95% by volume B 4 C; with 15 vol.% Mo and 85 vol.% B 4 C 7 and with 35 vol.% Mo (corresponds to 80 wt.%) and 65 vol.% B 4 C.
• the shaped articles produced according to the invention clearly show the separation of the embedded B 4 C particles (B 4 C dark, Mo light) from the surrounding Mo area. These differences are also confirmed in the scanning electron microscope and an X-ray scan of the same section. The X-ray fine structure analysis shows the metallic Mo in the compacts. The clear separation of B 4 C-containing areas and Mo-containing intermediate layers with thicknesses down to 3 / um was proven.
• Compacts were sintered using a semi-isostatic hot press with a compressive force of approx. 80 kN. Shaped bodies were produced and tested, the Mo contents ent held between 5% and 35% by volume. For this purpose, the homogeneously mixed powders of molybdenum (37 - 140 ⁇ m) and boron carbide (0.1 - 1360 ⁇ m) were filled into a graphite matrix. Square and round platelets were produced with punches movable from two sides under pressure of 10-30 MPa and at temperatures of 1850-2000 ° C.
• the heating rates were between 100 and 200 ° C / min.
• the holding times were between 10 and 20 minutes.
• the cooling rates were in the range of 100-200 ° C / min.
• the resulting shaped grains were clamped in a tool holder and fastened in the steel holder of a lathe.
• Various steels, including austenites, were machined with the cutting inserts.
• Al 2 O 3 was processed with the same arrangement, whereby both large-area removal and cuts were achieved. In addition, TaC and TiN surfaces could be removed.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Powder Metallurgy (AREA)
• Ceramic Products (AREA)

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Citations (6)

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• 1985
  • 1985-06-01 DE DE19853519710 patent/DE3519710A1/de active Granted
• 1986
  • 1986-02-18 EP EP86102025A patent/EP0204067A1/de not_active Withdrawn
  • 1986-04-12 DE DE8686105056T patent/DE3662153D1/de not_active Expired
  • 1986-05-21 US US06/865,477 patent/US4661155A/en not_active Expired - Fee Related
  • 1986-05-30 JP JP61123830A patent/JPS6230841A/ja active Pending

Patent Citations (6)

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