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CN-121992270-A - Double-crystal hard alloy and preparation method thereof

CN121992270ACN 121992270 ACN121992270 ACN 121992270ACN-121992270-A

Abstract

The application belongs to the technical field of powder metallurgy, and particularly relates to a double-crystal hard alloy and a preparation method thereof. The preparation method comprises the steps of mixing fine WC powder (2-4 microns), co powder, VC and Cr 3 C 2 for ball milling and spray granulation to obtain fine WC-Co composite powder, mixing coarse WC powder (8-12 microns), co powder and superfine WC powder (0.15-0.25 microns) for ball milling and spray granulation to obtain coarse WC-Co composite powder, and carrying out dry mixing, pressing and sintering on the fine WC-Co composite powder and the coarse WC-Co composite powder to obtain the double-crystal hard alloy, wherein Rockwell hardness is 87-90 HRA, fracture toughness is 14-17 MPa-m 1/2 , and bending strength is 2500-3000 MPa. According to the preparation method, coarse WC-Co composite powder and fine WC-Co composite powder are respectively prepared, so that the inhibitor can effectively inhibit the growth of fine WC grains in a sintering stage, meanwhile, the superfine WC can promote the growth of coarse WC grains, so that the prepared hard alloy presents obvious double-scale WC grain distribution, simultaneously has high hardness and high toughness, and the prepared double-crystal hard alloy has high density by carrying out pressing sintering after dry mixing.

Inventors

  • DENG TONGZHOU
  • HUANG SHIBING
  • XU GUOZUAN
  • ZHANG LONGHUI
  • ZHOU SHENGHUI
  • ZHONG JUN

Assignees

  • 崇义章源钨业股份有限公司

Dates

Publication Date
20260508
Application Date
20260409

Claims (10)

  1. 1. The preparation method of the bicrystal hard alloy is characterized by comprising the following steps of: S1, mixing first WC powder, first Co powder and vanadium-chromium powder, performing ball milling, and performing spray granulation to obtain first WC-Co composite powder, wherein the vanadium-chromium powder consists of VC and Cr 3 C 2 , and the particle size of the first WC powder is 2-4 mu m; S2, mixing the second WC powder, the second Co powder and the third WC powder, performing ball milling, and performing spray granulation to obtain second WC-Co composite powder, wherein the particle size of the second WC powder is 8-12 mu m, and the particle size of the third WC powder is 0.15-0.25 mu m; s3, dry-mixing the first WC-Co composite powder and the second WC-Co composite powder to obtain mixed powder; And S4, pressing and sintering the mixed powder, and cooling to obtain the bicrystal hard alloy.
  2. 2. The method for preparing the bicrystal hard alloy according to claim 1, wherein the mass fraction of each component in the first WC-Co composite powder is 86% -91% of the first WC powder, 8% -12% of the first Co powder and 1% -2% of the vanadium-chromium powder, and the mass ratio of VC to Cr 3 C 2 in the vanadium-chromium powder is 1 (0.8-1.2).
  3. 3. The method for preparing the bicrystal hard alloy according to claim 1, wherein the mass fraction of each component in the second WC-Co composite powder is 78% -88% of the second WC powder, 8% -12% of the second Co powder and 2% -10% of the third WC powder.
  4. 4. The method for preparing the bicrystal cemented carbide according to claim 1, wherein in the mixed powder, the mass fraction of the first WC-Co composite powder is 50% -80% and the mass fraction of the second WC-Co composite powder is 20% -50%.
  5. 5. The method for preparing the bicrystal cemented carbide according to claim 1, wherein the particle size of the first Co powder is 0.75-0.85 μm, and the particle size of the vanadium-chromium powder is 0.8-1 μm; the particle size of the second Co powder is 0.75-0.85 mu m.
  6. 6. The method for preparing the bicrystal cemented carbide according to claim 1, wherein the mass fraction of the particles with the granularity smaller than 100 meshes and larger than 270 meshes in the first WC-Co composite powder is larger than 70%; in the second WC-Co composite powder, the mass fraction of particles with the granularity smaller than 100 meshes and larger than 270 meshes is larger than 70%.
  7. 7. The method for preparing the bicrystal cemented carbide according to claim 1, wherein in the step S1, the ball milling speed is 300-400 rpm, the time is 16-24 h, the ball-to-material ratio is (4-6): 1, and the ball milling medium is alcohol; In the step S2, the rotation speed of the ball milling is 200-300 rpm, the time is 8-12 h, the ball-to-material ratio is (3-5): 1, and the ball milling medium is alcohol.
  8. 8. The method for preparing the bicrystal cemented carbide according to claim 1, wherein in the step S4, the pressed mixed powder is sintered by a low-pressure argon sintering process, the pressure of the low-pressure argon sintering process is 4-6 mpa, the temperature is 1400-1450 ℃, and the time is 40-80 min.
  9. 9. The bicrystal hard alloy is characterized in that the bicrystal hard alloy is prepared by the preparation method of any one of claims 1-8, wherein the grain size of fine WC in the bicrystal hard alloy is 0.4-1 μm, and the grain size of coarse WC is 1.5-4 μm.
  10. 10. The bicrystal cemented carbide of claim 9, wherein the bicrystal cemented carbide has a rockwell hardness of 87-90 hra, a fracture toughness of 14-17 mpa-m 1/2 , and a flexural strength of 2500-3000 mpa.

Description

Double-crystal hard alloy and preparation method thereof Technical Field The application belongs to the technical field of powder metallurgy, and particularly relates to a double-crystal hard alloy and a preparation method thereof. Background The hard alloy consists of a hard phase and a binding phase, and has the characteristics of toughness of metal and high hardness and high wear resistance of ceramic, so the hard alloy is also called as a metal ceramic material, and is widely applied to industries such as cutters, wire drawing dies, cold and hot rollers, printing heads, rock drill bits, oil well drill bits and the like. Common hard alloy is generally difficult to improve the hardness and the toughness simultaneously due to the contradiction between the hardness and the toughness. However, the combination of high hardness and good toughness is an indispensable requirement in industrial applications, and the manufacture of materials with these properties remains a great challenge. Thus, research on the co-reinforcement of hardness and toughness of cemented carbide has become one of the research hotspots in the field of cemented carbide for recent decades. The preparation method of the high-compactness bicrystal WC-Co hard alloy is an effective method, coarse WC particles in the bicrystal hard alloy have higher toughness, and fine WC particles can compensate for the loss of hardness, so that the bicrystal hard alloy can obtain higher strength and hardness at the same time. At present, the bicrystal hard alloy is mainly prepared by wet grinding to mix coarse and fine WC powder and binding phase powder and then powder metallurgy process, and after ultra-coarse WC is crushed by ball milling, coarse crystal size is easily recovered during sintering, abnormal growth is induced, and the structure is more uneven. At the same time, fine WC will dissolve rapidly and precipitate on the coarse WC grains resulting in a bimorph ratio and size that is more difficult to control. Disclosure of Invention In order to solve the problems, the application provides a double-crystal hard alloy and a preparation method thereof, wherein raw material WC powder with small granularity difference is adopted to inhibit excessive dissolution of fine WC grains and promote growth and development of coarse WC grains, so that the problem of insufficient performance of the double-crystal hard alloy caused by uneven growth of grains and overlarge double-crystal size difference is solved. The bicrystal hard alloy prepared by the method has obvious double-scale WC grain distribution, high confidentiality and good mechanical property. According to a first aspect of the present application, there is provided a method for preparing a bicrystal cemented carbide, comprising the steps of: S1, mixing first WC powder, first Co powder and vanadium-chromium powder, performing ball milling, and performing spray granulation to obtain first WC-Co composite powder, wherein the vanadium-chromium powder consists of VC and Cr 3C2, and the particle size of the first WC powder is 2-4 mu m; S2, mixing the second WC powder, the second Co powder and the third WC powder, performing ball milling, and performing spray granulation to obtain second WC-Co composite powder, wherein the particle size of the second WC powder is 8-12 mu m, and the particle size of the third WC powder is 0.15-0.25 mu m; s3, dry-mixing the first WC-Co composite powder and the second WC-Co composite powder to obtain mixed powder; And S4, pressing and sintering the mixed powder, and cooling to obtain the bicrystal hard alloy. Further, in the first WC-Co composite powder, the mass fraction of each component is 86% -91% of the first WC powder, 8% -12% of the first Co powder and 1% -2% of the vanadium-chromium powder, and the mass ratio of VC to Cr 3C2 in the vanadium-chromium powder is1 (0.8-1.2). Further, in the second WC-Co composite powder, the mass fraction of each component is 78% -88% of the second WC powder, 8% -12% of the second Co powder and 2% -10% of the third WC powder. Further, in the mixed powder, the mass fraction of the first WC-Co composite powder is 50% -80%, and the mass fraction of the second WC-Co composite powder is 20% -50%. Further, the particle size of the first Co powder is 0.75-0.85 mu m, and the particle size of the vanadium-chromium powder is 0.8-1 mu m; the particle size of the second Co powder is 0.75-0.85 mu m. Further, in the first WC-Co composite powder, the mass fraction of particles with the granularity smaller than 100 meshes and larger than 270 meshes is larger than 70%; in the second WC-Co composite powder, the mass fraction of particles with the granularity smaller than 100 meshes and larger than 270 meshes is larger than 70%. In the step S1, the rotation speed of the ball milling is 300-400 rpm, the time is 16-24 h, the ball-to-material ratio is (4-6), 1, and the ball milling medium is alcohol; In the step S2, the rotation speed of the ball milling is 200-30