Furnace system and method of use
A sintering furnace can include an outer shell defining an internal volume a reactive agent inlet configured to introduce a reactive agent into the internal volume; an insulation chamber within the outer shell; and a retort configured to retain an object. A method of operating a sintering furnace can include sintering a part precursor within a retort arranged within a chamber, wherein the chamber defines an intermediate volume between the retort and the chamber, wherein a sintering byproduct is oxidized within the intermediate volume.
1 . A method for operating a sintering furnace, comprising,
receiving a part precursor in a retort of the sintering furnace, wherein the part precursor is adhered to a build plate by an adhesive material;
heating the retort to a first debinding temperature, wherein the retort is maintained at the first debinding temperature for a first debinding time, wherein the part precursor releases from the build plate during the first debinding time;
heating the retort to a second debinding temperature greater than the first debinding temperature, wherein the retort is maintained at the second debinding temperature for a second debinding time, wherein binder is removed from the part precursor during the second debinding time; and
at a sintering temperature that is greater than the second debinding temperature, sintering the part precursor to form a part;
wherein the retort is arranged within a chamber, wherein the retort defines a retort volume, wherein the chamber defines an intermediate volume between the retort and the chamber that excludes the retort volume, the method further comprising, during or after at least one of the first debinding time or the second debinding time, introducing an oxidizing agent into the intermediate volume, wherein between the first debinding time and the sintering time an oxidizing agent concentration within the intermediate volume is greater than an oxidizing agent concentration within the retort volume.
2 . The method of claim 1 , wherein heating the retort to the first debinding temperature comprises heating the retort at a first heating ramp rate to the first debinding temperature, heating the retort to the second debinding temperature comprises heating the retort from the first debinding temperature to the second debinding temperature at a second heating ramp rate, and heating the retort to the sintering temperature comprises heating the retort from the second debinding temperature to the sintering temperature at a third heating ramp rate, wherein the third heating ramp rate is greater than the first or the second heating ramp rate.
3 . The method of claim 2 , wherein the first heating ramp rate is between 1 and 10° C./minute, and wherein the second heating ramp rate is between 1 and 10° C./minute.
4 . The method of claim 1 , wherein the first debinding temperature is between 100° C. and 300° C., wherein the second debinding temperature is between 300 and 500° C., and wherein the sintering temperature is between 900 and 1400° C.
5 . The method of claim 1 , wherein an inert gas is introduced in the retort volume, wherein the inert gas is preheated by a tortuous path in the retort before being introduced in the retort volume.
6 . The method of claim 1 , wherein after the second debinding time, the oxidizing agent flow rate is decreased.
7 . The method of claim 1 , further comprising, measuring an oxidized byproduct concentration, wherein the oxidizing agent flow rate is determined based on the oxidized byproduct concentration.
8 . The method of claim 1 , wherein the oxidizing agent concentration within the retort volume is at most approximately 100 ppm, and wherein the oxidizing agent concentration within the intermediate volume is at most 1000 ppm.
9 . The method of claim 1 , wherein the first and the second debinding time and the sintering time are each at least 10 minutes.
10 . The method of claim 9 , wherein during the first or the second debinding time, a ramp rate of a temperature of the sintering furnace is between 0.5-2° C./min.
11 . The method of claim 1 , wherein the part precursor is manufactured from a metal paste comprising:
metal scaffold particles with a D50 particle size; and
metal infiltrant particles with a D50 particle size that fits within an interstitial space between metal scaffold particles.
12 . The method of claim 11 , wherein the D50 particle size of the metal scaffold particles is between 10 μm and 20 μm, and wherein the D50 particle size of the metal infiltrant particles is between 2 μm and 10 μm.