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
  • C22C29/04—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 carbonitrides
• • 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
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/26—Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
  • Y10T428/263—Coating layer not in excess of 5 mils thick or equivalent
  • Y10T428/264—Up to 3 mils
  • Y10T428/265—1 mil or less

Definitions

• the invention relates to a cermet with a hard material content of 95 to 75% by mass and 5 to 25% by mass binder as the remainder made of cobalt and / or nickel, the hard material hare consisting of carbonitrides with a cubic B1 crystal structure and 30 to 60 masses % Ti, 5 to 25 mass% W, 5 to 15 mass% Ta, of which up to 70 mass% can be replaced by Nb, 0 to 12 mass% Mo, 0 to 5 mass% V, 0 to 2 mass% Cr, 0 to
• the (C + N) content in the carbonitride phase is> 80 mol%
• the nitrogen content N / (C + N) is between 0.15 and 0.7 and in the binder phase up to
• the hard material phases essentially have a core-edge structure.
• the invention further relates to a method for producing such a cermet by mixing, grinding, granulating and pressing a starting mixture containing corresponding constituents and then sintering.
• EP 0 344 421 A1 proposes a cermet which should either have an average grain size of the hard material phase in the surface layer compared to a core with a penetration depth of 0.05 mm, which is between 0.8 to 1.2 times the average grain size of the hard material phase in the cermet core or in the same penetration depth relates to a binder phase which corresponds to 0.7 to 1.2 times the average binder content of the cermet core or in which the hardness in the aforementioned penetration depth is between 0.95 and 1 , l times the average hardness of the cermet core.
• the starting mixture is sintered after grinding, mixing and pre-pressing, in a first stage up to 1300 ° C.
• EP 0 368 336 B1 describes a cermet substrate with a hard surface layer in which the region with the maximum hardness is present at a depth between 5 ⁇ m and 50 ⁇ m from the substrate surface, and the substrate surface has a hardness of 20 to 90% of maximum hardness.
• the pre-pressed mixture is subjected to an initial temperature increase to 1100 ° C. in a vacuum, a subsequent temperature increase from 1100 ° C. to a temperature range between 1400 ° C. and 1500 ° C. in a nitrogen atmosphere and a final sintering in a vacuum .
• EP 0 374 358 B1 describes a process for producing a cermet with 7 to 20% by weight binder phase and a hard phase made from titanium carbide, titanium nitride and / or titanium carbonitride with 35 to 59% by weight Ti, 9 to 29% by weight. %, 0.4 to 3.5% by weight of Mo, 4 to 24% by weight of at least one metal composed of Ta, Nb, V and zirconium, 5.5 to 9.5% by weight of N 2 and 4 , 5 to 12 wt .-% C.
• the formulated mixed, dried and pre-pressed mass is sintered in such a way that the temperature is raised to 1350 ° C.
• the nitrogen atmosphere being adjusted to 1 Torr at 1350 ° C., the nitrogen partial pressure together is gradually increased with the temperature increase from 1350 ° C. to the sintering temperature, the nitrogen atmosphere being set to 5 torr at the sintering temperature.
• EP 0 492 059 A3 describes a cermet body, the hardness of which is not less than 1 mm higher than in the interior of the cermet, the binder content being in a layer thickness can be minimized from 0.5 to 3 ⁇ m compared to the core substrate.
• the cermet should have a hard material coating in a thickness of 0.5 to 20 ⁇ m made of carbides, nitrides, oxides and borides of titanium and Al2O3.
• a green compact is first heated to a temperature between 1100 ° C. and 1400 ° C. under vacuum, then nitrogen gas is admitted to a pressure at which the partial nitrogen pressure is between 5 and 10 Torr, so that the substrate surface is denatured.
• the sintering and the final cooling are carried out under a non-oxidizing atmosphere, such as a vacuum or an inert gas atmosphere.
• the body is coated using CVD or PVD.
• EP 0 499 223 A1 proposes to produce a high-viscosity cermet, the relative concentration of the binder in a 10 ⁇ m thick layer near the surface to 5 to 50% of the average mean content of binder in the cermet core and in the layer below it from 10 ⁇ m to 100 ⁇ m Penetration depth to set the binder content to 70 to 100% relative to the cerium core, compressive stresses of 30 kgf / mm 2 and more being present on the surface.
• the sintering is carried out under nitrogen gas at a constant pressure of 5 to 30 torr and the cooling under vacuum at a cooling rate of 10 to 20 ° C./min.
• EP 0 515 340 A3 describes a cermet with a zone near the surface enriched in binder.
• EP 0 519 895 A1 discloses a cermet with a three-layered edge zone, in which the first layer is rich in TiN to a depth of 50 ⁇ m, the next layer has a penetration depth of 50 to 150 ⁇ m with a binder enrichment and the next layer from 150 ⁇ m to 400 ⁇ m with a binder depletion relative to the inside of the cermet core.
• the sintered body becomes this in an atmosphere of N 2 and / or NH3, optionally in combination with CH 4 , CO, C0 2 at 1100 ° C to 1350 ° C for one to 25 hours under atmospheric pressure or a pressure above 1.1 bar.
• the cermets known from the prior art either have different binder contents on the surface, which can be recognized by their spotty appearance, or tend to adhere the binder to the sintered base, which leads to changes in the composition in the contact zone because of the reactions involved.
• Further disadvantages of the cermets known according to the prior art are a partially high surface roughness and, in the case of increased binder metal contents in the surface, poor adhesion of wear protection layers applied there. If there is an increased proportion of nickel in the surface, CVD coating is not possible at all.
• the disadvantages mentioned speak in particular against the use of the cermet as a cutting insert for machining.
• the cermet mentioned in claim 1 which, in contrast to the previously known cermets, can only be measured in a surface layer determined by a penetration depth of 0.01 to 3 ⁇ m, and can be measured by an energy-dispersive micro analysis on a measuring surface> (0, 5 x 0.5) mm 2 , the content of Co and / or Ni binder in relation to the underlying cermet core areas is ⁇ 90% by mass, one in each case in the cermet core on the one hand and in the surface layer on the other uniform binder metal distribution is present.
• the cermet is present in a homogeneous structure, which should not rule out the presence of core edge structures of the hard material phase.
• the 0.01 to 3 ⁇ m thick surface layer relative to the underlying cermet core has a binding content of cobalt and / or nickel which is less than 30% by mass, while the titanium content is 110 to 130%.
• the sum of the contents of tungsten, tantalum and any proportions of molybdenum, niobium, vanadium and / or chromium in the surface layer mentioned is 70 to 100 masses relative to the underlying cermet core areas -%.
• the core areas lying under the surface layer mentioned have at least essentially a hard material phase with a core edge structure.
• the hard material phase in the surface layer can only be present homogeneously or with the core edge structure intended for the core, and possibly also partially.
• the cermet has a zone immediately below the surface layer to a depth of at least 50 ⁇ m, maximum 600 ⁇ m, which has a porosity according to ISO4505 of ⁇ A02 and ⁇ B02 and in the underlying core ⁇ A08 and ⁇ B04 having.
• the further preferably low roughness depths R ⁇ ⁇ 6 ⁇ m or Rg ⁇ 5 ⁇ m have an effect.
• the hardness HV30 is preferably constant in the surface area.
• the cermet in the surface layer with a depth between 0.01 and 3 ⁇ m has a Co and / or Ni binder content ⁇ 90% by mass with a Ti content between 100% and 120% relative to the core area and the The sum of the contents of W, Ta and possibly Mo, Nb, V, Cr is 80 to 100% by mass.
• the cermet can have one or more wear protection layers which consist of carbides or nitrides of titanium and / or of Al 2 O 3 , preferably applied by the CVD process.
• the cermet described is preferably produced by the method set out in claim 10. Thereafter, a mixture containing the components determined according to claim 1 is ground, granulated and pre-pressed and then sintered, preferably in sintering furnaces with graphite heating conductors. After pressing, the green body is first heated up to the melting temperature of the binder phase under vacuum with a pressure ⁇ 10 -1 bar, then further heated up to the sintering temperature, which is between 1450 to 1530 ° C., where the temperature is 0.2 to Hold for 2 hours and then the body is cooled to 1200 ° C.
• the last heating, holding and cooling is carried out in a gas mixture of N 2 and CO with an N 2 / (N 2 + CO) ratio between 0.1 and 0.9 under an average pressure of 10% to 80% of the mean alternately in a period between 40 and 240 sec, preferably 40 to 180 sec.
• the N / (N 2 + C0) ratio is determined by the equation
• the procedure described above is to be understood in such a way that an average pressure value remains constant over the entire heating up process from the melting point of the binding phase, sintering and cooling to 1200 ° C., but the pressure fluctuates periodically around this average pressure value, in particular due to a uniform deflection higher and lower values.
• the fluctuation amplitude can be sinusoidal or sawtooth-shaped or have shapes derived therefrom.
• only the pressure fluctuations described lead to a thin, uniform influencing of the surface layer of the type described above.
• the sintered body can be subjected to hot isostatic pressing under argon at temperatures near the sintering temperature and pressures above 30 bar after the sintering. While the body produced without the subsequent hot isostatic pressing shows a significantly reduced binder content of less than 30% by mass in the surface layer up to a maximum penetration depth of 3 ⁇ m, the subsequently hot isostatically pressed body sometimes has higher binder contents, which, however, is still below 90%. relative to the binder content in the cermet core.
• cermet bodies are only subjected to sintering.
• the setting of the gas atmosphere during sintering can be seen from FIGS. 1 and 2. Show it Fig. 1 shows the linear relationship between the
• Fig. 2 shows the dependence of the setting of the middle
• the respective value x represents the relative nitrogen content in the cermet, namely the ratio N / (C + N) and the value y the setting of the gas mixture N 2 / (N 2 + CO).
• the limit values are predetermined by cermet nitrogen contents between 0.15 and 0.7, to which settings of the gas mixture of 0.1 and 0.9 are assigned. All the values in between can be taken from the graphical representation, fluctuations up or down of 10% are permitted. The same applies to the representation according to FIG. 2, where the ordinate y represents the mean pressure in bar and the abscissa represents the binder content x in mass%.
• the mean pressure to be set is 20 mbar, with a binder content of 5% by mass 6 mbar, with deviations from the mean value of up to 10% being permitted here as well.
• the pressures set in the sintering furnace then fluctuate around a constant mean pressure value, namely by alternating at least 10% upwards and downwards.
• step 3 with the proviso that no CO was blown in and the set N 2 pressure was constant at 20 mbar.
• Example 1 invention-moderator cermet equal
• the total binder content is 16.9% by mass.
• the starting mixture was, as is known from the prior art, ground, mixed and pre-pressed. The following process steps were then used:
• a comparative body was subjected to the same process steps 1, 2 and 4, process step 3, however, with the proviso that no CO was blown in and the N pressure was constantly 20 mbar.
• Example 4 cermet according to the invention

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Cutting Tools, Boring Holders, And Turrets (AREA)
• Powder Metallurgy (AREA)
• Golf Clubs (AREA)
• Investigating And Analyzing Materials By Characteristic Methods (AREA)
• Rolls And Other Rotary Bodies (AREA)

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• 1995
  • 1995-03-29 US US08/716,340 patent/US5856032A/en not_active Expired - Fee Related
  • 1995-03-29 EP EP95913058A patent/EP0758407B1/fr not_active Expired - Lifetime
  • 1995-03-29 JP JP7527925A patent/JPH09512308A/ja active Pending
  • 1995-03-29 WO PCT/DE1995/000434 patent/WO1995030030A1/fr active IP Right Grant
  • 1995-03-29 ES ES95913058T patent/ES2112053T3/es not_active Expired - Lifetime
  • 1995-03-29 AT AT95913058T patent/ATE163203T1/de not_active IP Right Cessation

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