Polycrystalline cubic boron nitride composite material

Patent metadata

Field	Value
Publication number	US-11634796-B2
Application number	US-202017772834-A
Country	US
Kind code	B2
Filing date	Nov 25, 2020
Priority date	Dec 6, 2019
Publication date	Apr 25, 2023
Grant date	Apr 25, 2023

Abstract

This disclosure relates a polycrystalline cubic boron nitride, PCBN, composite material for use in friction stir welding. The PCBN composite material comprises tungsten (W), rhenium (Re) and aluminium (Al) in the binder matrix material.

First claim

The invention claimed is:

1. A polycrystalline cubic boron nitride, PCBN, composite material consisting of: between 60 and 90 vol. % cubic boron nitride, cBN, particles and between 40 and 10 vol. % binder matrix material in which the cBN particles are dispersed, the cBN particles having an average grain size lying in the range 8 to 20 μm, the binder matrix material comprising between 90 and 99 wt. % an alloy of the refractory metals tungsten (W) and rhenium (Re) and which further comprises aluminium (Al) in a form other than as an oxide, the binder phase including an interface layer on the cBN grains, said interface layer comprising borides or nitrides of Al, characterised in that said aluminium (Al) is present in a quantity between 2 and 10 wt. % of the binder matrix material and the interface layer has an average thickness which lies in the range 100-250 nm.

2. The PCBN composite material according to claim 1 , in which the interface layer covers at least 50% of the surface of the cBN grains.

3. The PCBN composite material according to claim 1 , in which the interface layer is a reacted layer comprising Al, B and N, and comprises an aluminium nitride and/or an aluminium boride.

4. The PCBN composite material as claimed in claim 3 , in which a composition of the reacted layer varies throughout its thickness.

5. The PCBN composite material as claimed in claim 1 , in which the interface layer comprising Al has an average thickness which lies in the range 170 to 190 nm.

6. The PCBN composite material as claimed in claim 1 , in which a total oxygen content of the composite material is less than 3% measured as described herein.

7. The PCBN composite material as claimed in claim 1 , comprising 65 to 75 vol. % cBN particles and 25 to 30 vol. % binder matrix.

8. The PCBN composite material as claimed in claim 1 , in which a composition of the W—Re alloy lies in the range 72 wt. %-77 wt. % tungsten (W), and correspondingly 28 wt. %-23 wt. % Re.

9. The PCBN composite material as claimed in claim 1 , in which grains of the W—Re alloy have an average grain size lying in the range 3 to 5 μm.

10. The PCBN composite material as claimed in claim 1 , further comprising WC impurities within the binder matrix material, said impurities being present in an amount of less than 1 wt. % of the PCBN composite material.

11. The PCBN composite material as claimed in claim 1 , further comprising a rhenium-aluminium alloy in the binder matrix material.

12. The PCBN composite material as claimed in claim 1 , in which the cBN particles have a sharpness in the range of between 0.40 and 0.70, wherein the sharpness is measured as described herein.

13. The PCBN composite material as claimed in claim 1 , which has a Young's Modulus of between 500 and 560 GPa, derived using the speed of sound method and calculated as described herein.

14. The PCBN composite material as claimed in claim 1 , which has a speed of sound between 8 and 9 km/s.

15. A method of fabricating a polycrystalline cubic boron nitride, PCBN, composite material, said method comprising the steps:
providing a matrix precursor powder comprising the refractory metals tungsten (W) and rhenium (Re) and which further comprises between 2 and 10 wt. % of the matrix precursor powder of Al in a form other than an oxide;
providing a cubic boron nitride, cBN, powder comprising particles of cBN,
mixing the matrix precursor powder and the cBN powder;
compacting the mixed matrix precursor powder and cBN powder to form a green body;
outgassing the green body at a temperature between 800° C. and 1150° C.;
sintering the green body at a temperature between 1300° C. and 1600° C. and a pressure of at least 3.5 GPa to form the PCBN composite material of claim 1 .

16. The method as claimed in claim 15 , in which the composite material is as claimed in claim 2 .

17. The method as claimed in claim 15 , in which the matrix precursor powder comprises separate particles of W, Re, and Al.

18. The method as claimed in claim 15 in which the matrix precursor powder comprises particles combining W and Re, either pre-alloyed or as separate phases such as one coating the other.

19. The method as claimed in claim 15 in which the step of mixing comprises mixing the matrix precursor powder and the cBN powder using a mixing vessel free of exposed metal or WC surfaces.

20. The method as claimed in claim 15 , in which the step of mixing comprises mixing the matrix precursor powder and the cBN powder in a polymer or polymer coated mixing pot.

21. The method as claimed in claim 15 , comprising the following sub-steps:
adding the cBN and aluminium powders together;
mixing in a vessel for 2 minutes at 800 rpm, followed by 2 minutes at 1200 rpm;
adding half of the tungsten-rhenium powder to the cBN and aluminium powders;
mixing in a vessel for 2 minutes at 800 rpm, followed by 2 minutes at 1200 rpm;
adding the remaining half of the tungsten-rhenium powder to the cBN and aluminium powders; and
mixing in a vessel for 2 minutes at 800 rpm, followed by 2 minutes at 1200 rpm.

22. The method as claimed in claim 15 , in which the step of sintering comprises sintering at a temperature of 1500° C.

23. The method as claimed in claim 15 , in which the step of sintering comprises sintering at a pressure in the range 4.0-6.0 GPa.

Assignees

• Element Six Uk Ltd

Inventors

• Ghosh Santonu
• Rodriguez Suarez Teresa
• Andersin Stig Åke

Classifications

• C22C1/05

  Mixtures of metal powder with non-metallic powder (C22C1/08 takes precedence) · CPC title

• C22C1/051

  Making hard metals based on borides, carbides, nitrides, oxides or silicides; Preparation of the powder mixture used as the starting material therefor · CPC title

• B22F2998/10

  Processes characterised by the sequence of their steps · CPC title

• B22F2302/205

  Cubic boron nitride · CPC title

• B22F2301/20

  Refractory metals · CPC title