Aluminum foam core piston with coaxial laser bonded aerogel/ceramic head

Abstract

A method of forming an insulated composite piston head may include: creating a preformed aluminum or aluminum alloy foam core; suspending the preformed foam core in a piston head mold; forming a molded piston head and removing it from the mold; depositing an insulating material on at least one surface of the molded piston head; performing at least one machining operation on the molded piston head so it conforms to a predetermined specification for the insulated composite piston head; and optionally applying a lubricious piston coating to at least a portion of the outer surface of the insulated composite piston head.

What is claimed is: 
     
         1 . A method of forming an insulated composite piston head, the method comprising:
 creating a preformed aluminum or aluminum alloy foam core;   suspending the preformed foam core in a piston head mold;   injecting or casting molten aluminum or an aluminum alloy into the mold through gates or traps to form a metallic layer that at least partially encapsulates the foam core, thereby, forming a molded piston head;   removing the molded piston head from the mold;   depositing an insulating material on at least one surface of the molded piston head;   performing at least one machining operation on the molded piston head such that the molded piston head conforms to a predetermined specification for the insulated composite piston head; and   optionally, applying a lubricious piston coating to at least a portion of the outer surface of the insulated composite piston head.   
     
     
         2 . The method according to  claim 1 , wherein the insulating material is an aerogel, a ceramic material, or a mixture thereof. 
     
     
         3 . The method according to  claim 2 , wherein the insulating material comprises an aerogel that is encapsulated by a ceramic or aluminum shell. 
     
     
         4 . The method according to  claim 1 , wherein the metallic layer has a thickness of about 4 mm or more. 
     
     
         5 . The method according to  claim 1 , wherein the insulating material exhibits a thickness that is about 1 mm or less. 
     
     
         6 . The method according to  claim 1 , wherein the foam core has a porosity that is between about 20% to about 50%. 
     
     
         7 . The method according to  claim 1 , wherein the piston head further comprises a lubricious piston coating on at least a portion of the outer surface of the insulated composite piston head. 
     
     
         8 . The method according to  claim 7 , wherein the lubricious piston coating is a silicone or polytetrafluoroethylene. 
     
     
         9 . The method according to  claim 1 , wherein the insulating material is applied using a coaxial laser deposition process. 
     
     
         10 . The method according to  claim 9 , wherein the coaxial laser deposition process comprises:
 providing a high pressure gas source;   placing a metal powder in a feeder container;   placing the molded piston head into a closed chamber;   allowing the high pressure gas to force the metal powder from the feeder through a spray nozzle onto a surface of the molded piston head in the closed chamber;   using a coaxial laser to fuse the powder that is applied to the surface of the molded piston head; and   removing excess powder from the closed chamber.   
     
     
         11 . The method according to  claim 10 , wherein the coaxial laser deposition process further comprises: rotating the molded piston head and indexing the coaxial laser and spray nozzle using a robotic arm and a pyrometer to control the temperature of the surface on the molded piston head. 
     
     
         12 . The method according to  claim 10 , wherein the coaxial laser deposition process further comprises: using a separator to isolate excess metal powder that is reused by mixing the excess metal powder with the metal powder in the feeder container.