Sinterable article with removable support structures

Abstract

Support structures are used in certain additive fabrication processes to permit fabrication of a greater range of object geometries. For additive fabrication processes with materials that are subsequently sintered into a final part, an interface layer may be fabricated between the object and support in order to inhibit bonding between adjacent surfaces of the support structure and the object during sintering. Interface layers suitable for manufacture with an additive manufacturing system may resist the formation of bonds between a support structure and an object during subsequent sintering processes.

What is claimed is: 
     
         1 . An article comprising:
 an object formed of a build material, the build material including a sinterable powdered material for forming a final part at a sintering temperature, wherein the build material includes a binder system containing one or more binders retaining the sinterable powdered material in a net shape of the object prior to densifying the sinterable powdered material into the final part;   a support structure for the object, the support structure positioned adjacent to a surface of the object to provide mechanical support during processing of the object into the final part, the support structure formed of a second material having a shrinkage rate during processing matched to the build material; and   an interface layer disposed between the support structure and the surface of the object, the interface layer containing a composition that resists bonding of the support structure to the surface of the object through the interface layer during sintering, wherein the composition of the interface layer includes a ceramic powder having a sintering temperature substantially higher than the build material.   
     
     
         2 . The article of  claim 1  wherein the one or more binders retain the net shape of the object during processing of the object into the final part, wherein processing of the object into the final part includes debinding the net shape to remove at least a portion of the one or more binders and sintering the net shape to join and densify the sinterable powdered material. 
     
     
         3 . The article of  claim 1  wherein the sinterable powdered material includes a metallic powder. 
     
     
         4 . The article of  claim 1  wherein the second material is the build material. 
     
     
         5 . The article of  claim 1  wherein the second material of the support structure contains the ceramic powder of the interface layer. 
     
     
         6 . The article of  claim 1  wherein the interface layer and the support structure are formed of substantially the same composition. 
     
     
         7 . The article of  claim 1  wherein the ceramic powder has a substantially smaller mean particle size than the sinterable powdered material for forming the final part, and wherein the ceramic powder is distributed interstitially between particles of a second sinterable powdered material on an outer surface of the support structure to resist necking between the sinterable powdered material of the build material and the second sinterable powdered material of the support structure around the outer surface during sintering at the sintering temperature, thereby providing the interface layer. 
     
     
         8 . The article of  claim 7  wherein the ceramic powder has a mean particle size of less than one micron. 
     
     
         9 . The article of  claim 8  wherein the sinterable powdered material has a second mean particle size of about fifteen to thirty-five microns. 
     
     
         10 . The article of  claim 7  wherein the ceramic powder has a mean particle size at least one order of magnitude smaller than a similarly measured mean particle size of the sinterable powdered material. 
     
     
         11 . The article of  claim 1  wherein the interface layer physically excludes the support structure and the object, wherein the ceramic powder has a substantially greater mean particle size than the sinterable powdered material of the object, and further wherein the ceramic powder is disposed in a second binder system that retains a shape of the interface layer. 
     
     
         12 . The article of  claim 11  wherein the second binder system retains a shape of the interface layer during an onset of a thermal sintering cycle at the sintering temperature. 
     
     
         13 . The article of  claim 1  wherein the build material includes a powdered metallurgy material. 
     
     
         14 . The article of  claim 1  wherein the binder system includes submicron particles selected to facilitate sintering of the sinterable powdered material. 
     
     
         15 . The article of  claim 14  wherein the submicron particles include an element selected for alloying with the sinterable powdered material. 
     
     
         16 . The article of  claim 14  wherein the submicron particles of the binder system have a composition substantially identical to the sinterable powdered material and a size distribution with a mean particle size at least one order of magnitude smaller than the sinterable powdered material. 
     
     
         17 . The article of  claim 1  wherein the sinterable powdered material has a distribution of particle sizes with a mean diameter of between ten and fifty microns. 
     
     
         18 . The article of  claim 1  wherein the interface layer includes a selective embrittlement material selected to introduce crack defects into at least one of the support structure and the object at the interface layer during sintering into the final part. 
     
     
         19 . The article of  claim 18  wherein the sinterable powdered material includes an alloy of at least one of aluminum, steel, and copper, and wherein the selective embrittlement material includes at least one of antimony, arsenic, bismuth, lead, sulfur, phosphorous, tellurium, iodine, bromine, chlorine, and fluorine. 
     
     
         20 . The article of  claim 1  wherein the interface layer includes a preceramic polymer that decomposes into a ceramic during sintering at the sintering temperature.