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CN-121992268-A - Low-cobalt tough nano gradient hard alloy and preparation method and application thereof

CN121992268ACN 121992268 ACN121992268 ACN 121992268ACN-121992268-A

Abstract

The invention discloses a low-cobalt tough nano gradient hard alloy and a preparation method and application thereof, and relates to the technical field of hard alloy materials, wherein the hard alloy comprises a WC hard phase and a Co-based binding phase, and a surface layer, a transition layer and a core layer are sequentially arranged along the thickness direction of a product; the mass fraction of Co in the surface layer is 0.5-3.0 wt%, the mass fraction of Co in the transition layer is 3.0-5.0 wt%, the mass fraction of Co in the core layer is 5.0-7.0 wt%, cr 3 Si nano precipitated phase is contained in the hard alloy, the average grain diameter of the Cr 3 Si nano precipitated phase is 2-20 nm, the density is not lower than 1X 1022m ‑3 , and meanwhile, the interface enrichment distribution is realized. The invention realizes more stable comprehensive toughening effect in a low-cobalt system, and improves the service consistency and service life stability of the material under the working condition of precision machining.

Inventors

  • JU JIA
  • YANG HONGWEN
  • ZHANG ZIYUN

Assignees

  • 晟准模具科技(昆山)有限公司

Dates

Publication Date
20260508
Application Date
20260224

Claims (10)

  1. 1. The low-cobalt tough nano gradient hard alloy is characterized by comprising a WC hard phase and a Co-based binding phase, wherein a surface layer, a transition layer and a core layer are sequentially arranged along the thickness direction of a product; the mass fraction of Co in the surface layer is 0.5-3.0 wt%, the mass fraction of Co in the transition layer is 3.0-5.0 wt%, and the mass fraction of Co in the core layer is 5.0-7.0 wt%; The hard alloy contains Cr 3 Si nano precipitated phase, the average grain diameter of the Cr 3 Si nano precipitated phase is 2 nm-20 nm, the density is not lower than 1 multiplied by 1022m -3 , and the Cr 3 Si nano precipitated phase is in interface enrichment distribution.
  2. 2. The low-cobalt tough nano-gradient cemented carbide according to claim 1, wherein the WC hard phase has an average grain size of 0.2 μm to 0.6 μm.
  3. 3. The low-cobalt tough nano-gradient cemented carbide according to claim 1, wherein the thickness of the surface layer is 0.1 mm-1.0 mm, and the thickness of the transition layer is 0.2 mm-2.0 mm.
  4. 4. The low-cobalt tough nano-gradient cemented carbide according to claim 1, further comprising a grain inhibitor NbC, wherein the mass fraction of NbC is 0.05wt% to 0.50wt%, and a Nb-rich carbide segregation layer is formed at the interface between WC and Co-based binder phase, and coexists with the Cr 3 Si nano-precipitated phase near the interface.
  5. 5. The method for preparing the low-cobalt tough nano-gradient cemented carbide according to any one of claims 1 to 4 is characterized by comprising the following steps: Step 1, providing WC powder, carrying out composite coating operation of a Cr-containing precursor and a Si-containing precursor on the WC powder, and forming a Cr/Si-rich precursor coating layer with the thickness of 5-50 nm on the surface of WC particles to obtain coated WC powder; step 2, treating the coated WC powder into a carbon nano structure, mixing the carbon nano structure with Co powder according to a target composition ratio, and uniformly mixing the mixture in a ball milling mode to obtain composite raw material powder; Step 3, granulating the composite raw material powder, and compacting the granulated powder in a cold isostatic pressing mode to obtain a formed green body; step 4, sintering the inside of the formed green body into a primary sintering neck structure through pre-sintering treatment to obtain a pre-sintered body; Step 5, carrying out gradient sintering on the pre-sintered body, adopting multi-region temperature control, monitoring and adjusting the temperature difference delta T between the core part and the surface layer of the product in real time to be less than or equal to 50 ℃, controlling the dew point of the sintering atmosphere to be less than or equal to-40 ℃ and adjusting the carbon potential through atmosphere proportion to keep the carbon potential in a carbon potential window for inhibiting eta phase generation and inhibiting free graphite precipitation, so as to form a Co-based binding phase gradient structure; And 6, in a high-temperature heat preservation stage of the Co-based binder phase gradient structure, carrying out sectional heat preservation treatment within the range of 1420-1450 ℃, reacting the Cr/Si-rich precursor coating layer at the interface of WC and the binder phase, and generating Cr 3 Si nano precipitated phase in situ to obtain the hard alloy.
  6. 6. The method of preparing a low cobalt strong and tough nano-gradient cemented carbide according to claim 5, wherein the composite coating operation is performed by contacting WC powder with a Cr-containing salt solution and a Si-containing sol or a silicon source precursor and depositing the same into a film, followed by drying and heat treatment in a reducing atmosphere to solidify and stabilize the Cr/Si-rich precursor coating layer.
  7. 7. The method for preparing the low-cobalt tough nano gradient hard alloy is characterized in that the carbon potential window is constrained based on the dew point of less than or equal to minus 40 ℃, one of a CO/CO 2 atmosphere system or a CH 4 /H 2 atmosphere system is selected as a carbon regulating gas source, and the volume fraction ratio of two components in the atmosphere system is regulated on line to ensure that the carbon potential in the furnace is stably maintained in an effective carbon potential control window; the effective carbon potential control window is defined as satisfying the carbon balance condition of "no formation of eta phase and no precipitation of free graphite" simultaneously throughout the sintering cycle.
  8. 8. The method of claim 5, wherein the grain inhibitor NbC is added simultaneously during the uniform mixing by ball milling, and the grain inhibitor NbC is preferentially attached to and distributed on the surfaces of WC particles by mechanical shearing and collision.
  9. 9. The method for preparing the low-cobalt tough nano-gradient cemented carbide according to claim 5, wherein the treatment of the coated WC powder into the carbon nano-structure is an in-situ vapor deposition treatment of the coated WC powder, wherein a carbon source is deposited on the surface of the WC powder to form the carbon nano-structure, and the WC powder forming the carbon nano-structure is mixed with Co powder in a proportioning manner; the total content of the carbon nano structure is 0.03-0.30 wt%, and after sintering, part of the carbon nano structure is converted and reserved into a carbon nano derivative bridging structure.
  10. 10. The application of the low-cobalt tough nano-gradient cemented carbide according to any one of claims 1 to 4 in a high-precision electronic die, wherein the high-precision electronic die comprises a semiconductor packaging processing die and a precision connector processing die.

Description

Low-cobalt tough nano gradient hard alloy and preparation method and application thereof Technical Field The invention relates to the technical field of hard alloy materials, in particular to a low-cobalt tough nano gradient hard alloy and a preparation method and application thereof. Background In recent years, WC-based cemented carbide has been continuously developed in the fields of high-precision electronic dies, semiconductor packaging, precision connector processing, and the like, and research and industry have been systematically explored around the directions of grain refining, cobalt reduction, functional gradient, interface strengthening, and the like. The hardness maintenance, wear-resistant stability and service consistency of the material are continuously improved by regulating and controlling the content and distribution of the cobalt-based binding phase, optimizing the sintering thermal field and atmosphere conditions and introducing the nano-scale dispersed phase. Meanwhile, aiming at the working conditions of local load concentration and thermomechanical coupling in micro-feature processing, interface structure design and nano precipitation regulation and control gradually become important means for improving comprehensive performance. Under the low cobalt condition, the performance of the hard alloy is more sensitively limited by the structural stability and the load transmission capability of the WC-cobalt-based bonding phase interface, and the interface microcracks are easy to initiate and expand under the cyclic stress and the local heat influence, so that the crack resistance reliability and the service life stability are further weakened. In the prior art, although the hardness and wear resistance can be improved by reducing the cobalt content of the surface layer or introducing a disperse phase, if the interface strengthening is insufficient or the position of a precipitated phase is uncontrollable, strengthening contribution is difficult to effectively act on a key area of the interface, so that the cooperative improvement of the strength and toughness in a low-cobalt system is limited, and the requirements of a high-precision die on wear resistance, crack resistance and combination are difficult to meet. Disclosure of Invention In view of the above, the application provides a low-cobalt tough nano gradient hard alloy, and a preparation method and application thereof. According to one aspect of the present disclosure, there is provided a low-cobalt tough nano-gradient cemented carbide, including, the cemented carbide includes a WC hard phase and a Co-based binder phase, and a surface layer, a transition layer, and a core layer are sequentially set in a thickness direction of the article; the mass fraction of Co in the surface layer is 0.5-3.0 wt%, the mass fraction of Co in the transition layer is 3.0-5.0 wt%, and the mass fraction of Co in the core layer is 5.0-7.0 wt%; The hard alloy contains Cr 3 Si nano precipitated phase, the average grain diameter of the Cr 3 Si nano precipitated phase is 2 nm-20 nm, the density is not lower than 1 multiplied by 1022m -3, and the Cr 3 Si nano precipitated phase is in interface enrichment distribution. According to one aspect of the present disclosure, there is provided a method for preparing a low cobalt strong and tough nano-gradient cemented carbide, comprising the steps of: Step 1, providing WC powder, carrying out composite coating operation of a Cr-containing precursor and a Si-containing precursor on the WC powder, and forming a Cr/Si-rich precursor coating layer with the thickness of 5-50 nm on the surface of WC particles to obtain coated WC powder; step 2, treating the coated WC powder into a carbon nano structure, mixing the carbon nano structure with Co powder according to a target composition ratio, and uniformly mixing the mixture in a ball milling mode to obtain composite raw material powder; Step 3, granulating the composite raw material powder, and compacting the granulated powder in a cold isostatic pressing mode to obtain a formed green body; step 4, sintering the inside of the formed green body into a primary sintering neck structure through pre-sintering treatment to obtain a pre-sintered body; Step 5, carrying out gradient sintering on the pre-sintered body, adopting multi-region temperature control, monitoring and adjusting the temperature difference delta T between the core part and the surface layer of the product in real time to be less than or equal to 50 ℃, controlling the dew point of the sintering atmosphere to be less than or equal to-40 ℃ and adjusting the carbon potential through atmosphere proportion to keep the carbon potential in a carbon potential window for inhibiting eta phase generation and inhibiting free graphite precipitation, so as to form a Co-based binding phase gradient structure; And 6, in a high-temperature heat preservation stage of the Co-based binder phase gradient structure, carrying out secti