MIM braze preforms
A method of making a braze preform includes: providing a mixture of a brazing alloy in metallic powder form and a binder; melting the binder and forming the mixture into a preform having a preselected shape; removing a majority of the binder from the preform; and heating the preform to remove the remainder of the binder and to sinter the metallic powder together. The preform may include a wear-resistant material therein. Such preforms may be used to form a braze joint between two metallic components, or to produce a metallic component with a wearcoated surface.
1. A method of assembling a swirler assembly by brazing, comprising:
providing a flare cone, a swirl cup, a deflector and a dome plate;
providing a mixture of a brazing alloy in metallic powder form and a binder;
melting the binder and forming the mixture by metal injection molding into a first preform, a second preform, and a third preform;
after the step of melting the binder and forming the mixture into performs, leaching the preforms to remove a majority of the binder from the preforms;
after the step of removing a portion of the binder from the preforms, heating the preforms to a temperature below the liquidus temperature of the metallic powder but high enough to cause the metallic powder to fuse together to simultaneously remove the remainder of the binder and sinter the metallic powder together;
after the step of heating the preforms to fuse together the metallic powder, holding the preforms at the temperature to consolidate the preforms;
placing the first preform between the flare cone and an inner cylindrical surface of the swirl cup, placing the second preform into an annular groove defined by the swirl cup, and placing the third preform at a juncture of the deflector and the dome plate;
heating the flare cone, swirl cup, deflector and dome plate and the preforms to a temperature below the melting point of the flare cone, swirl cup, deflector and dome plate and above the melting point of the preforms to cause the braze alloy to melt and flow; and
allowing the braze alloy to cool to form a bond between the flare cone and swirl cup and the deflector and dome plate.
2. The method of claim 1 further comprising performing a hot isostatic pressing treatment on the preforms after the heating step and before placing the preforms adjacent to or within the joints.
3. The method of claim 1 wherein the binder is leached by washing the preforms with a solvent selected to dissolve the binder but not the metallic powder.
4. The method of claim 1 wherein the heating is carried out in a chamber having a controlled composition atmosphere.
5. The method of claim 4 wherein the atmosphere is an inert gas.
6. The method of claim 4 wherein the atmosphere is a reducing atmosphere.
7. The method of claim 1 wherein the metallic powder is an alloy of nickel or cobalt.
8. The method of claim 1 wherein the metallic powder includes a melting point suppressant.