Manufacture of composite components by powder metallurgy

1. A method for preparing an article, the method comprising:

compacting a mixture of a first pre-alloyed powder and a lubricant to thereby form a green part having a green strength sufficient to permit mechanical handling;

applying a slurry to a surface of the green part to thereby form a slurry coated green part, wherein the slurry comprises a second pre-alloyed powder, a binder, and a solvent;

wherein the first pre-alloyed powder is a Ni-based, Co-based, or Fe-based powder, and the second pre-alloyed powder is Ni-based or Co-based powder; and

heating the coated green part to a temperature below the solidus temperature of the first pre-alloyed powder and between the solidus temperature and the liquidus temperature of the second pre-alloyed powder to thereby solid state sinter the first pre-alloyed powder into a sintered core and to liquid state sinter the second pre-alloyed powder into a continuous alloy coating over the sintered core.

2. The method of claim 1 further comprising drying the slurry-coated green part to remove the solvent between the applying step and the heating step.

3. The method of claim 1 further comprising:

drying the slurry-coated green part to remove the solvent between the applying step and the final heating step; and

heating the coating layer to a temperature between about 200° C. and about 500° C. to remove the binder before the final heating step.

4. The method of claim 1 wherein the heating to a temperature between the solidus temperature and the liquidus temperature of the second pre-alloyed powder comprises heating to a temperature between about 900° C. and about 1350° C.

5. The method of claim 1 wherein the first pre-alloyed powder is a Fe-based powder and the second pre-alloyed powder is Co-based alloy powder comprising between about 21 wt % and about 35 wt % Cr, between about 4 wt % and about 19 wt % W, up to about 3 wt % Ni, up to about 5 wt % Fe, between about 0.4 wt % and about 3.5 wt % C, up to about 1.5 wt % Mn, between about 0.1 wt % and about 1.5 wt % Si, and up to about 1.5 wt % Mo, and the balance Co.

6. The method of claim 1 comprising, in sequence:

compacting the mixture of the first pre-alloyed powder and the lubricant to thereby form the green part having the green strength sufficient to permit mechanical handling;

applying the slurry to the surface of the green part to thereby form the slurry coated green part, wherein the slurry comprises the second pre-alloyed powder, the binder, and the solvent;

drying the slurry-coated green part to remove the solvent;

heating the coating layer to a temperature between about 200° C. and about 500° C. to remove the binder;

heating the coated green part to the temperature below the solidus temperature of the first pre-alloyed powder and between the solidus temperature and the liquidus temperature of the second pre-alloyed powder to thereby solid state sinter the first pre-alloyed powder into the sintered core and to liquid state sinter the second pre-alloyed powder into the continuous alloy coating over the sintered core.

7. The method of claim 1 comprising, in sequence:

compacting the mixture of the first pre-alloyed powder and the lubricant to thereby form the green part having the green strength sufficient to permit mechanical handling;

applying the slurry to the surface of the green part to thereby form the slurry coated green part, wherein the slurry comprises the second pre-alloyed powder, the binder, and the solvent;

drying the slurry-coated green part to remove the solvent;

heating the coating layer to a temperature between about 200° C. and about 500° C. to remove the binder;

heating the coated green part to a temperature between about 900° C. and about 1350° C. to thereby solid state sinter the first pre-alloyed powder into the sintered core and to liquid state sinter the second pre-alloyed powder into the continuous alloy coating over the sintered core.

8. The method of claim 1 wherein a ratio of weight of the second pre-alloyed powder to weight of the solvent is from 2:1 to about 15:1.

9. The method of claim 1 wherein a ratio of weight of the second pre-alloyed powder to weight of the solvent is from about 6:1 to about 13:1.

10. The method of claim 1 wherein a ratio of weight of the second pre-alloyed powder to weight of the solvent is from about 9:1 to about 11:1.

11. The method of claim 1 wherein the first pre-alloyed powder is a Fe-based powder and the second pre-alloyed powder is Co-based alloy powder comprising between about 26 wt % and about 34 wt % Cr, between about 4 wt and about 18 wt % Mo, up to about 3 wt % Ni, up to about 3 wt % Fe, between about 0.2 wt % and about 3 wt % C, up to about 1.5 wt % Mn, between about 0.5 wt % and about 1.5 wt % Si, up to about 0.5 wt % B, and the balance Co.

12. The method of claim 1 wherein the first pre-alloyed powder is a Fe-based powder and the second pre-alloyed powder is Co-based alloy powder comprising between about 26 wt % and about 33 wt % Cr, up to about 14 wt % Mo, between about 0.1 wt % and about 3.5 wt % C, up to about 1 wt % Mn, up to about 1.5 wt % Si, balance Co, and one or both of between about 8 wt % and about 20 wt % Fe and between about 1 wt % and about 8 wt % Ni.

13. The method of claim 1 wherein the first pre-alloyed powder is a Fe-based powder and the second pre-alloyed powder is Co-based alloy powder comprising between about 8 and about 18 wt % Cr, between about 20 and about 33 wt % Mo, between about 0.5 and about 4 wt % Si, and balance cobalt.

14. The method of claim 1 wherein the first pre-alloyed powder is a Fe-based powder and the second pre-alloyed powder is Ni-based alloy powder comprising between about 14 and 28 wt % Cr, between about 24 and about 34 wt % Mo, between about 1 and about 4 wt % Si, up to about 0.1 wt % C, up to about 3 wt % Fe, up to about 2 wt % Co, and balance Ni.

15. The method of claim 1 wherein the first pre-alloyed powder is a Fe-based powder and the second pre-alloyed powder is Ni-based alloy powder comprising between about 0.2 and about 6 wt %. Fe, between about 0.5 and about 4 wt %. B, between about 1 and about 5 wt. % Si, between about 0.03 to about 1 wt. % C, and balance Ni.

16. A method for preparing an article, the method comprising:

compacting a mixture of a first pre-alloyed powder and a lubricant to thereby form a green part having a green strength sufficient to permit mechanical handling;

applying a slurry to a surface of the green part to thereby form a slurry coated green part, wherein the slurry comprises a second pre-alloyed powder, a binder, and a solvent;

heating the coated green part to a temperature below the solidus temperature of the first pre-alloyed powder and between the solidus temperature and the liquidus temperature of the second pre-alloyed powder to thereby solid state sinter the first pre-alloyed powder into a sintered core and to liquid state sinter the second pre-alloyed powder into a continuous alloy coating over the sintered core;

wherein the first pre-alloyed powder is a Fe-based powder and the second pre-alloyed powder is a Co-based alloy powder comprising between about 20 wt % and about 35 wt % Cr, between about 2 wt % and about 15 wt % W, between about 6 wt % and about 24 wt % Ni, up to about 4 wt % Fe, between about 0.1 wt % and about 2 wt % C, up to about 1.5 wt % Mn, between about 0.3 wt % and about 3 wt % Si, up to about 3 wt % B, and the balance Co.

17. A method for preparing an article, the method comprising:

compacting a mixture of a first pre-alloyed powder and a lubricant to thereby form a green part having a green strength sufficient to permit mechanical handling;

applying a slurry to a surface of the green part to thereby form a slurry coated green part, wherein the slurry comprises a second pre-alloyed powder, a binder, and a solvent, wherein a ratio of weight of the second pre-alloyed powder to weight of the solvent is from 2:1 to about 15:1;

wherein the first pre-alloyed powder is a Ni-based, Co-based, or Fe-based powder, and the second pre-alloyed powder is Ni-based or Co-based powder; and

heating the coated green part to a temperature between about 900° C. and about 1350° C. to thereby sinter the first pre-alloyed powder into a sintered core and to sinter the second pre-alloyed powder into a continuous alloy coating over the sintered core.

18. The method of claim 17 further comprising drying the slurry-coated green part to remove the solvent between the applying step and the heating step.

19. The method of claim 17 further comprising:

drying the slurry-coated green part to remove the solvent between the applying step and the final heating step; and

heating the coating layer to a temperature between about 200° C. and about 500° C. to remove the binder before the final heating step.

20. The method of claim 17 wherein said heating is to a temperature between about 950° C. and about 1050° C.

21. The method of claim 17 wherein the ratio of weight of the second pre-alloyed powder to weight of the solvent is from about 6:1 to about 13:1.

22. The method of claim 17 wherein the ratio of weight of the second pre-alloyed powder to weight of the solvent is from about 9:1 to about 11:1.

23. A method for preparing an article, the method comprising:

compacting a mixture of a first pre-alloyed powder and a lubricant to thereby form a green part having a green strength sufficient to permit mechanical handling;

applying a slurry to a surface of the green part to thereby form a slurry coated green part, wherein the slurry comprises a second pre-alloyed powder, a binder, and a solvent;

heating the coated green part to a temperature between about 900° C. and about 1350° C. to thereby sinter the first pre-alloyed powder into a sintered core and to sinter the second pre-alloyed powder into a continuous alloy coating over the sintered core;

wherein the first pre-alloyed powder is a Fe-based powder and the second pre-alloyed powder is Co-based alloy powder comprising between about 21 wt % and about 35 wt % Cr, between about 4 wt % and about 19 wt % W, up to about 3 wt % Ni, up to about 5 wt % Fe, between about 0.4 wt % and about 3.5 wt % C, up to about 1.5 wt % Mn, between about 0.1 wt % and about 1.5 wt % Si, and up to about 1.5 wt % Mo, and the balance Co.

24. A method for preparing an article, the method comprising:

compacting a mixture of a first pre-alloyed powder and a lubricant to thereby form a green part having a green strength sufficient to permit mechanical handling;

applying a slurry to a surface of the green part to thereby form a slurry coated green part, wherein the slurry comprises a second pre-alloyed powder, a binder, and a solvent;

heating the coated green part to a temperature between about 900° C. and about 1350° C. to thereby sinter the first pre-alloyed powder into a sintered core and to sinter the second pre-alloyed powder into a continuous alloy coating over the sintered core;

wherein the first pre-alloyed powder is a Fe-based powder and the second pre-alloyed powder is Co-based alloy powder comprising between about 20 wt % and about 35 wt % Cr, between about 2 wt % and about 15 wt % W, between about 6 wt % and about 24 wt % Ni, up to about 4 wt % Fe, between about 0.1 wt % and about 2 wt % C, up to about 1.5 wt % Mn, between about 0.3 wt % and about 3 wt % Si, up to about 3 wt % B, and the balance Co.

25. A method for preparing an article, the method comprising:

compacting a mixture of a first pre-alloyed powder and a lubricant to thereby form a green part having a green strength sufficient to permit mechanical handling;

applying a slurry to a surface of the green part to thereby form a slurry coated green part, wherein the slurry comprises a second pre-alloyed powder, a binder, and a solvent;

heating the coated green part to a temperature below the solidus temperature of the first pre-alloyed powder and between the solidus temperature and the liquidus temperature of the second pre-alloyed powder to thereby solid state sinter the first pre-alloyed powder into a sintered core and to liquid state sinter the second pre-alloyed powder into a continuous alloy coating over the sintered core;

wherein the first pre-alloyed powder is a Fe-based powder and the second pre-alloyed powder is a Fe-based alloy powder comprising between about 4 and about 10 wt. % Co, between about 0.6 and about 5 wt. % C, between about 2 and about 30 wt. % Cr, between about 0.1 and about 4 wt. % Mn, between about 4 and about 22 wt. % Mo, between about 0.5 and about 3 wt. % Si, between about 3 and about 9 wt. % W, and balance Fe.