US 2003/0156963 A1 · Techniques for infiltration of a powder metal skeleton by a similar alloy with melting point depressed

Abstract

In infiltrating a porous metal skeleton an infiltrant composition is used similar to that of the powder skeleton, but with the addition of a melting point depressant. The infiltrant quickly fills the skeleton. As the melting point depressant diffuses into the base powder, the liquid, may undergo diffusional solidification and the material eventually homogenizes. Maintaining the infiltrant at a liquidus composition for the infiltration temperature typically ensures that the bulk composition or properties will remain uniform throughout the part, particularly in the direction of infiltration. Success of such an infiltration is enhanced by effective means of maintaining the molten infiltrant at a liquidus composition. It is also beneficial, in some cases, for the time scale of the infiltration to be much faster than the time scale of the diffusion of the melting point depressant and the subsequent solidification and homogenization. The relative rates of infiltration and diffusion/solidification rate are significantly impacted by the choice of materials system. Other factors also influence these rates. They include: selection of powder size (diameter), shape, surface roughness, and size distribution, feeding liquid from different locations, liquid feeder channels, smoothing of the part surface with fine powder and affecting infiltrant fluid properties. Various material systems are also disclosed, as are methods of designing a process of infiltrating a part, including binary and ternary and higher component systems. Homogeneous composition may be direction of infiltration.

Claims80

Dependent claims

A method for fabricating a substantially metal part, comprising the steps of:

a. providing a skeleton of interconnected adhered metal powder having a network of interconnected porosities throughout, said metal powder composed of at least two elements;
b. providing an infiltrant comprising:
i. the same at least two elements as are in the skeleton;
and
ii. melting point depressant (MPD);
the infiltrant having a composition that is a liquidus composition for an infiltration temperature;
and
c. infiltrating said skeleton with said infiltrant, at approximately said infiltration temperature, whereby essentially no erosion of said skeleton transpires.

5 more elements

A method for fabricating a substantially metal part, comprising the steps of:

a. providing a skeleton of interconnected adhered metal powder having a network of interconnected porosities throughout a geometry, said metal powder composed of at least one element, chosen as in step e below, with powder particle composition and characteristics chosen as in step e below;
b. providing an infiltrant comprising:
i. the same elements as are in the skeleton;
and
ii. melting point depressant;
the infiltrant having a composition, chosen as in step e below;
c. infiltrating said skeleton at an infiltration temperature chosen as in step e below, with said infiltrant in liquid form;
d. subjecting said infiltrated skeleton to conditions such that after said step of infiltration has substantially completed such that said skeleton geometry is fully infiltrated, a portion of said melting point depressant diffuses from said infiltrated porosities into said metal powder, and at least partial diffusional solidification occurs;
and
e. choosing said metal powder composition, melting point depressant, infiltrant composition and infiltration temperature and metal particle size, size distribution, and surface roughness, such that said infiltrant infiltrates throughout substantially all of said network of interconnected porosities before essentially any of said diffusional solidification has occurred;
whereby said infiltrated skeleton is substantially free of compositional gradient along a direction of infiltration.

8 more elements

A method for infiltrating a substantially metal part, comprising the steps of:

a. providing a skeleton having:
i. an interconnected adhered metal powder body having a network of interconnected porosities throughout, said porosities having a characteristic pore size;
ii. at least one infiltrant contact surface;
and
iii. at least one feeder channel having a characteristic diameter d that is at least three times said pore size, said feeder channel extending from said infiltrant contact surface to a first internal region of said network of porosities;
b. providing, an infiltrant supply;
c. subjecting said infiltrant supply to an infiltration temperature under conditions that melt at least a portion of said infiltrant supply;
d. contacting said infiltrant contact surface of said skeleton to said melted infiltrant supply, such that liquid infiltrant passes through said feeder channel to said internal region;
and
e. subjecting said skeleton to conditions such that said liquid infiltrant infiltrates said interconnected porosities of said skeleton, including said internal region.

7 more elements

A method for infiltrating a substantially metal part, comprising the steps of:

a. providing a skeleton of interconnected adhered metal first powder having a surface and a network of interconnected porosities throughout, said powder having a relatively larger characteristic particle size;
b. substantially covering said surface of said skeleton with a covering layer comprising relatively fine metallic powder, said relatively fine powder having a characteristic size that is significantly smaller than said relatively larger characteristic size;
c. providing, in a vessel, an infiltrant supply;
d. subjecting said infiltrant supply to an infiltration temperature, under conditions that melt a portion of said infiltrant supply;
e. contacting said skeleton to said melted infiltrant supply, such that infiltrant is drawn into said skeleton through said relatively larger metal powder by capillary action;
f. infiltrating said interconnected porosities of said relatively larger metal powder with said melted infiltrant and infiltrating said covering layer with said melted infiltrant, via said interconnected porosities of said relatively larger metal powder.

3 more elements

A method for infiltrating a substantially metal part, comprising the steps of:

a. providing a skeleton of interconnected adhered metal powder having a network of interconnected porosities throughout, said powder particles having:
i. a size and shape such that, if smooth, said particles would have a nominal surface area;
and
ii. a surface texture that gives rise to an actual surface area that exceeds said nominal surface area by between approximately 25% and 500% of said nominal surface area;
b. providing, an infiltrant supply comprising:
i. the same elements as are in the skeleton;
and
ii. melting point depressant;
c. subjecting said infiltrant supply to an infiltration temperature, under conditions that melt at least a portion of said infiltrant supply;
d. contacting said skeleton to said melted infiltrant supply, such that liquid infiltrant is drawn into said skeleton through said network of porosities by capillary action;
e. infiltrating said interconnected porosities of said skeleton with said melted infiltrant.
f. subjecting said infiltrated skeleton to temperature conditions such that a portion of said melting point depressant diffuses from said infiltrated porosities into said metal powder;
and
g. subjecting said infiltrated skeleton to temperature conditions such that infiltrant that has infiltrated said porosities, solidifies;
wherein a comparison network of porosities identical to said network, but for having a representative particle surface area equal to said nominal surface, area having a diffusional solidification related penetration distance limit (PL), said skeleton having a geometry and dimension such that a region of said network of interconnected porosities is spaced from said infiltrant contact surface a distance that exceeds said penetration distance limit of said comparison network;
whereby said infiltrant infiltrates said skeleton to said region of said network by capillarity through said interconnected porosities of particles having a surface area that exceeds said smooth surface area, beyond said penetration distance limit, from said infiltrant contact surface.

13 more elements

Dependencies are inferred from the claim text.

Techniques for infiltration of a powder metal skeleton by a similar alloy with melting point depressed

Life of this patent

Techniques for infiltration of a powder metal skeleton by a similar alloy with melting point depressed

Life of this patent

Abstract

Claims80