Selective laser melting / sintering using powdered flux
An additive manufacturing process ( 110 ) wherein a powder ( 116 ) including a superalloy material and flux is selectively melted in layers with a laser beam ( 124 ) to form a superalloy component ( 126 ). The flux performs a cleaning function to react with contaminants to float them to the surface of the melt to form a slag. The flux also provides a shielding function, thereby eliminating the need for an inert cover gas. The powder may be a mixture of alloy and flux particles, or it may be formed of composite alloy/flux particles.
1. A process comprising:
placing a first layer of powder comprising alloy material and flux material on a surface;
indexing an energy beam across the first layer of powder to selectively melt a region of alloy under an overlying layer of slag;
allowing the alloy and slag to solidify;
removing the slag; and
repeating the placing, indexing and removing steps with a pattern of indexing effective to form a desired component shape;
wherein the alloy material comprises a superalloy composition beyond a zone of weldability defined on a graph of superalloys plotting titanium content verses aluminum content, wherein the zone of weldability is upper bounded by a line intersecting the titanium content axis at 6 wt. % and intersecting the aluminum content axis at 3 wt. %; and
wherein the process is performed at an ambient room temperature without preheating the surface, and the slag acts as a blanket that causes the region of alloy to cool slowly and evenly.
2. The process of claim 1 , further comprising forming the layer of powder as a mixed layer of alloy particles and flux particles wherein a mesh size range of the alloy particles and a mesh size range of the flux particles overlap.
3. The process of claim 1 , further comprising forming the layer of powder as a layer of composite alloy and flux particles comprising particles of the alloy material coated with the flux material.
4. The process of claim 1 , further comprising post weld heat treating the component shape without inducing reheat cracking.
5. The process of claim 1 performed without providing a protective cover of inert gas.
6. The process of claim 1 , wherein the flux material is formulated to contribute to a deposit chemistry of the solidified region of alloy.
7. The process of claim 1 , wherein the energy beam is a laser beam, and the flux material provides an energy absorption and trapping function that converts the laser beam into heat energy and facilitates control of heat input within 1-2%.
8. An additive manufacturing process wherein the improvement comprises:
selectively heating respective regions of successive layers of powder comprising alloy material and flux material to form molten and solidified regions of alloy covered by molten and solidified slag; and
removing the solidified slag before heating each next successive layer;
wherein the alloy material comprises a superalloy composition beyond a zone of weldability defined on a graph of superalloys plotting titanium content verses aluminum content, wherein the zone of weldability is upper bounded by a line intersecting the titanium content axis at 6 wt. % and intersecting the aluminum content axis at 3 wt. %; and
wherein the process is performed without providing a protective cover of inert gas, and the slag shields the molten and solidified regions of alloy from the atmosphere.
9. The process of claim 8 , wherein the layer of powder comprises mixed alloy particles and flux particles wherein a mesh size range of the alloy particles and a mesh size range of the flux particles overlap.
10. The process of claim 8 , wherein the layer of powder is a layer of composite alloy and flux particles comprising particles of the alloy material coated with the flux material.
11. The process of claim 8 , further comprising:
repeating the heating and removing steps to form a desired component shape; and
post weld heat treating the component shape without inducing reheat cracking.
12. The process of claim 8 , wherein the flux material is formulated to contribute to a deposit chemistry of the solidified regions of alloy.
13. The process of claim 8 , wherein the energy beam is a laser beam, and the flux material provides an energy absorption and trapping function that converts the laser beam into heat energy and facilitates control of heat input within 1-2%.
14. A process comprising:
forming a powder comprising a superalloy material and a flux material;
using the powder in an additive manufacturing process to form a desired component shape in a sequence of layers; and
removing slag from each layer before forming the next layer;
wherein the alloy material comprises a superalloy composition beyond a zone of weldability defined on a graph of superalloys plotting titanium content verses aluminum content, wherein the zone of weldability is upper bounded by a line intersecting the titanium content axis at 6 wt. % and intersecting the aluminum content axis at 3 wt. %;
wherein the slag provides a heat blanket that controls the heat input, and the flux is formulated to produce a shielding gas, wherein the process is performed without the use of an inert gas flow, hot box, or chill plate.
15. The process of claim 14 , further comprising forming the powder to comprise particles of the superalloy material coated with the flux material.