Post-fabrication forging treatment

Abstract

A method of modifying a grain structure of a metal article includes disposing at least a portion of a metal article in a molten salt bath in a pressure vessel. The molten salt bath has bath temperature that is below a melting point temperature of the metal article. The method also includes pressuring the molten salt bath in the pressure vessel to a forging pressure sufficient to cause pressure-driven grain changes in the metal article.

What is claimed is: 
     
         1 . A method of modifying a grain structure of a metal article, the method comprising:
 disposing at least a portion of a metal article in a molten salt bath in a pressure vessel, the molten salt bath at a bath temperature that is below a melting point temperature of the metal article; and   pressurizing the molten salt bath in the pressure vessel to a forging pressure sufficient to cause pressure-driven grain changes in the metal article.   
     
     
         2 . The method of  claim 1 , further comprising, after maintaining the molten salt bath at the forging pressure for a forging period, disposing at least the portion of the metal article in a quench medium. 
     
     
         3 . The method of  claim 2 , wherein disposing at least the portion of the metal article in the quench medium comprises:
 extracting molten salt from the pressure vessel; and   introducing the quench medium into the pressure vessel.   
     
     
         4 . The method of  claim 3 , further comprising venting, from the pressure vessel, gases released by the quench medium. 
     
     
         5 . The method of  claim 2 , further comprising, after disposing at least the portion of the metal article in the quench medium, heat treating the metal article in the molten salt bath at a pressure less than the forging pressure. 
     
     
         6 . The method of  claim 5 , wherein heat treating the metal article in the molten salt bath comprises:
 extracting the quench medium from the pressure vessel; and   introducing molten salt into the pressure vessel.   
     
     
         7 . The method of  claim 1 , further comprising, before disposing at least the portion of the metal article in the molten salt bath, fabricating the metal article using one or more of an additive manufacturing process, a casting process, or a machining process. 
     
     
         8 . The method of  claim 1 , wherein the bath temperature is greater than a recrystallization temperature of the metal article. 
     
     
         9 . The method of  claim 1 , wherein the pressure-driven grain changes include grain boundary alignment. 
     
     
         10 . A system for modifying a grain structure of a metal article, the system comprising:
 a pressure vessel sized to receive a metal article;   a molten salt tank configured to store molten salt; and   a first pump coupled to the molten salt tank and to the pressure vessel and configured to provide the molten salt to the pressure vessel to at least partially submerge the metal article in a molten salt bath at a bath temperature that is below a melting point temperature of the metal article and to pressurize the molten salt bath to a forging pressure sufficient to cause pressure-driven grain changes in the metal article.   
     
     
         11 . The system of  claim 10 , further comprising a mold or a die defining a target feature shape for the metal article and configured to be coupled to the metal article while the metal article is at least partially submerged in the molten salt bath. 
     
     
         12 . The system of  claim 10 , further comprising:
 a controller coupled to the first pump, the controller including a processor and a memory, the memory storing instructions that are executable by the processor to cause the processor to send one or more first control signals to the first pump to control operation of the first pump.   
     
     
         13 . The system of  claim 12 , wherein the instructions define a process recipe associated with the metal article, wherein the process recipe specifies the bath temperature, the forging pressure, and a forging time based at least on a metal or alloy of the metal article. 
     
     
         14 . The system of  claim 13 , wherein the process recipe is further based on target grain characteristics of the metal article. 
     
     
         15 . The system of  claim 12 , further comprising:
 a quench medium tank configured to store a quench medium; and   a second pump coupled to the quench medium tank and to the pressure vessel, the second pump configured to provide, responsive to one or more second control signals from the controller, the quench medium to the pressure vessel to at least partially submerge the metal article in a quench bath.   
     
     
         16 . The system of  claim 15 , further comprising a vapor control system coupled to the pressure vessel and configured to vent, from the pressure vessel, gases released by the quench medium. 
     
     
         17 . The system of  claim 15 , further comprising:
 one or more temperature sensors disposed in the pressure vessel and coupled to the controller to provide one or more temperature feedback signals to the controller; and   one or more pressure sensors disposed in the pressure vessel and coupled to the controller to provide one or more pressure feedback signals to the controller.   
     
     
         18 . A forging pressure vessel comprising:
 one or more insulated walls defining an interior region and configured to withstand pressure, within the interior region, of at least five thousand pounds per square inch;   one or more molten salt ports through the one or more insulated walls and configured to transport molten salt into the interior region, out of the interior region, or both, to subject a metal article within the interior region to a molten salt bath at a bath temperature that is below a melting point temperature of the metal article and at a forging pressure sufficient to cause pressure-driven grain changes in the metal article; and   one or more quench medium ports through the one or more insulated walls and configured to transport a quench medium into the interior region, out of the interior region, or both.   
     
     
         19 . The forging pressure vessel of  claim 18 , further comprising:
 a temperature sensor disposed in the interior region and configured to provide a temperature signal to a first connector that is external to the one or more insulating walls; and   a pressure sensor disposed in the interior region and configured to provide a pressure signal to a second connector that is external to the one or more insulating walls.   
     
     
         20 . The forging pressure vessel of  claim 18 , further comprising one or more vapor ports through the one or more insulated walls and configured to vent gases released by the quench medium.