Surface modified particulate and sintered or injection molded products
Disclosed are interfacially modified particulate and polymer composite material for use in injection molding processes, such as metal injection molding and additive process such as 3D printing. The composite material is uniquely adapted for powder metallurgy processes. Improved products are provided under process conditions through surface modified powders that are produced by extrusion, injection molding, additive processes such as 3D printing, Press and Sinter, or rapid prototyping.
1. A method of making an object with an additive manufacturing system, the method comprises:
depositing a filament, with the system comprising a digitally controlled applicator, in a controlled x-y plane with subsequent z-direction filament application to obtain a preform object; the filament comprising:
about 70 to 1 wt. % of a thermoplastic polymer; and
about 99 to 30 wt. % of a metal particulate, dispersed in the polymer, the particulate having a particle size of less than 500 microns, and an exterior coating of interfacial modifier in an amount of about 0.02 to 2.0 wt. %, all percentages based on the weight of the filament; and
sintering the preform object to remove the polymer and bond the particulate forming the object.
2. The method of claim 1 wherein the preform is mechanically shaped prior to sintering.
3. The method of claim 1 wherein the filament is deposited at a rate of about 15 to 200 mm-sec −1 .
4. The method of claim 1 wherein the preform object is sintered at a temperature greater than about 1000° C.
5. The method of claim 4 wherein in sintering the preform object, the preform object is sintered by increasing the temperature at a rate greater than 100° C. per hour beginning at an initial temperature.
6. The method of claim 5 wherein the initial temperature is less than 100° C.
7. The method of claim 1 wherein the preform object comprises a first filament and a second filament the second filament comprising either a particulate or a polymer different than the first filament.
8. The method of claim 1 wherein the sintering is conducted in a non-oxidizing atmosphere.
9. The method of claim 1 wherein the non-oxidizing atmosphere is a reducing atmosphere.