Method for fabricating an open-porous metal foam body, metal foam body fabricated this way as well as its applications
The invention relates to a method for fabricating an open-porous metal foam body with a nickel base alloy, to a metal foam body fabricated this way as well as advantageous applications for the separation of specific components and pollutants from fluid flows. On the occasion, according to the set object open-porous metal foam bodies which have improved mechanical properties, and in addition an enlarged specific surface and/or increased surface roughness are to be provided. During fabricating it is proceeded such that an open-porous base foam body made of nickel or a nickel base alloy is coated with a liquid binding agent. Subsequent to this, a mixture of a powdery nickel base alloy and an organic component the temperature of phase transformation of which is at least 30 degrees centigrade from its solid phase to the liquid phase is deposited. The temperature should then be below the respective temperature of phase transformation. By means of thermal treatment the binding agent and the organic component are expelled, a portion of the powder particles is sintered, and a further portion of the powder particles is connected with the surface of the base foam body in a material-fit manner via sintering bridges.
1. A method for fabricating an open-porous metal foam body, the method comprising:
applying a liquid binding agent to an open-porous base foam body that is made of a nickel base alloy;
after applying the liquid bindinq agent to the open-porous base foam body, depositing a powder mixture of a powdery nickel base alloy and a powdery organic component upon the open-porous base foam body, wherein the powdery organic component has a phase transition temperature, wherein deposition occurs at a temperature below the phase transition temperature, and wherein the powdery nickel base alloy includes at least 15 wt % chromium; and
subsequent to the deposition, conducting a thermal treatment at a temperature between 1,200° C. and 1,250° C. in an inert or reducing atmosphere,
wherein the thermal treatment (a) expels the liquid binding agent and the powdery organic component, (b) sinters a first portion of the powdery nickel base alloy, and (c) connects, in a material-fit manner, a second portion of the powdery nickel base alloy to the open-porous base foam body via sintering bridges, wherein at least 20% of particles in the second portion of the powdery nickel base alloy maintain their particle shape during the thermal treatment, and
wherein a nickel component of the powdery nickel base alloy is smaller than a nickel component of the nickel base alloy.
2. The method of claim 1 , wherein the powdery organic component comprises at least one of a paraffin powder or a wax powder.
3. The method of claim 1 , wherein the powdery organic component is used in the form of a substance mixture.
4. The method of claim 1 , wherein the nickel base alloy includes at least one further alloy element selected from the group consisting of carbon, chromium, molybdenum, iron, cobalt, niobium, titanium, aluminum, boron, zirconium, manganese, silicon and lanthanum.
5. The method of claim 1 , wherein the powdery nickel base alloy includes at least 18 wt % chromium.
6. The method of claim 1 , wherein the powdery organic component comprises at least 0.05 wt % of the mixture.
7. The method of claim 1 , wherein the powdery nickel base alloy consists of particles that are smaller than about 60 μm and that have a median particle size between about 20 μm and about 35 μm.
8. The method of claim 1 , wherein:
the powdery nickel base alloy includes at least 18 wt % chromium; and
the powdery organic component comprises at least one of a paraffin powder or a wax powder.
9. The method of claim 1 , wherein the thermal treatment also sinters a surface portion of the open-porous base foam body.
10. The method of claim 1 , wherein the thermal treatment is conducted with a maximum temperature in the range between 1220° C. and 1250° C.
11. The method of claim 1 , further comprising, before depositing the powder mixture, removing the liquid binding agent from cavities in the open-porous base foam body by pressing with an absorbent pad.
12. The method of claim 1 , wherein the powdery organic component has a melting temperature between 140° C. and 145° C.