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 a shaped article with an injection molding manufacturing system, the method comprises
forming a composite, the composite comprising about 70 to 1 wt. % of a thermoplastic polymer; and about 99 to 30 wt. % of a 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 composite; and
injection molding the composite to form a preform object and;
sintering the preform object to remove the polymer and bond the particulate forming a shaped object; wherein the particulate comprises a metal alloy particle, a ceramic particle, a bi-metal particle or blends thereof.
2. The method of claim 1 wherein the preform object is sintered in one step with no debinding step.
3. The method of claim 1 wherein the ceramic particle is a tungsten carbide.
4. The method of claim 1 wherein the alloy particle is a stainless steel.
5. The method of claim 1 wherein the ceramic particle comprises glass.
6. The method of claim 5 wherein the particle is a hollow sphere or a solid sphere.
7. The method of claim 1 wherein the bi-metal particle comprises at least copper, iron, nickel, tungsten or molybdenum.
8. The method of claim 1 wherein the preform object is mechanically shaped prior to sintering.
9. The method of claim 1 wherein the preform object is sintered at a temperature greater than about 1000° C.
10. 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.
11. The method of claim 10 wherein the initial temperature is less than 100° C.
12. The method of claim 1 wherein the preform object comprises a first composite and a second composite, the second composite comprising either a particulate or a polymer different than the first.
13. The method of claim 1 wherein the sintering is conducted in a reducing atmosphere.
14. The method of claim 1 wherein the preform object composite has a volume packing of the particulate of greater than 80%.
15. The method of claim 1 wherein the preform object composite has a volume packing of the particulate of greater than 85%.
16. The method of claim 1 wherein the preform object composite has a volume packing of the particulate of greater than 90%.