Method for imaging inclusions in investment castings

Abstract

A method for imaging inclusions in metal or metal alloy castings is described. One embodiment of the present method first involves casting a metal or metal alloy article using an investment casting mold where the mold facecoat, and perhaps one or more of the mold backup layers, comprises an imaging agent distributed substantially uniformly throughout in amounts sufficient for imaging inclusions. The facecoat preferably comprises an intimate mixture of a refractory material and the imaging agent. Intimate mixtures can be produced in a number of ways, but a currently preferred method is to cocalcine the refractory material, such as yttria, with the imaging agent, such as gadolinia. The facecoat also can comprise plural mold-forming materials and/or plural imaging agents. The difference between the linear attenuation coefficient of the article and the linear attenuation coefficient of the imaging agent should be sufficient to allow imaging of the inclusion throughout the article. The metal or metal alloy article is then analyzed for inclusions by N-ray analysis. The method also can include the step of analyzing the metal or metal alloy by X-ray analysis. The imaging agent, typically a metal oxide or salt, comprises a material selected from the group consisting of boron, neodymium, samarium, europium, gadolinium, dysprosium, holmium, erbium, ytterbium, lutetium, iridium, physical mixtures thereof and chemical mixtures thereof.

We claim:  
     
         1 . A method for determining whether a metal or metal alloy article has inclusions, comprising: 
 providing a cast metal or metal alloy article made using a casting mold comprising ytterbium as an N-ray imaging agent in an amount sufficient for imaging inclusions; and    determining whether the article has inclusions by N-ray imaging.    
     
     
         2 . The method according to  claim 1  where the N-ray imaging agent is ytterbia.  
     
     
         3 . A method for casting a metal or metal alloy article, comprising: 
 providing a casting mold comprising an N-ray imaging agent which includes a material selected from the group consisting of lithium, boron, neodymium, samarium, europium, gadolinium, dysprosium, holmium, ytterbium, lutetium, iridium, physical mixtures thereof and chemical mixtures thereof; and    casting a metal or metal alloy article using the casting mold.    
     
     
         4 . The method according to  claim 3  where the N-ray imaging agent includes a material selected from the group consisting of samarium, gadolinium, dysprosium, physical mixtures thereof and chemical mixtures thereof.  
     
     
         5 . The method according to  claim 3  where the N-ray imaging agent includes gadolinium.  
     
     
         6 . The method according to  claim 5  where the N-ray imaging agent is gadolinia.  
     
     
         7 . The method according to  claim 3  where the casting mold includes a facecoat having a refractory material selected from the group consisting of yttria, zirconia, alumina, calcia, silica, zirconia, titania, tungsten, physical mixtures thereof, and chemical mixtures thereof.  
     
     
         8 . A method for determining whether a metal or metal alloy article has inclusions, comprising: 
 providing a cast metal or metal alloy article made using a casting mold comprising an imaging agent in amounts sufficient for imaging inclusions; and    determining whether the article has inclusions by N-ray analysis using a film image recorder.    
     
     
         9 . The method according to  claim 8  where the film image recorder is a camera.  
     
     
         10 . The method according to  claim 8  where the film image recorder is a light-emitting fluorescent screen.  
     
     
         11 . The method according to  claim 8  where determining whether the article has inclusions by N-ray analysis comprises using neutrons selected from the group consisting of fast, epithermal, thermal and cold neutrons, or combinations thereof.  
     
     
         12 . The method according to  claim 11  where the neutrons are cold neutrons.  
     
     
         13 . The method according to  claim 11  where the neutrons are epithermal neutrons.  
     
     
         14 . The method according to  claim 8  where the imaging agent is selected from the group consisting of lithium, boron, neodymium, samarium, europium gadolinium, dysprosium, holmium, ytterbium, lutetium, iridium, physical mixtures thereof, and chemical mixtures thereof, and the mold includes a facecoat refractory material selected from the group consisting of yttria, zirconia, alumina, calcia, silica, zircon, titania, tungsten, physical mixtures thereof, and chemical mixtures thereof.  
     
     
         15 . A method for real time detection of inclusions in a metal or metal alloy article, comprising: 
 providing a cast metal or metal alloy article made using a casting mold comprising an imaging agent in amounts sufficient for imaging inclusions; and    determining whether the article has inclusions by real time N-ray analysis.    
     
     
         16 . The method according to  claim 15  where determining comprises analyzing N-ray images produced in real time using an image displaying device.  
     
     
         17 . The method according to  claim 16  where the image displaying device is a light-emitting fluorescent screen.  
     
     
         18 . A method for real time detection of inclusions in a metal or metal alloy article, comprising: 
 casting a metal or metal alloy article using a mold having a facecoat comprising an imaging agent distributed substantially uniformly throughout in amounts sufficient for imaging inclusions; and    analyzing the article for inclusions by real time N-ray analysis.    
     
     
         19 . The method according to  claim 18  where the mold is an investment casting mold, and the imaging agent is distributed substantially uniformly in at least a facecoat layer.  
     
     
         20 . The method according to  claim 18  where the step of analyzing further comprises X-ray analysis.  
     
     
         21 . The method according to  claim 18  where the imaging agent includes a material selected from the group consisting of lithium, boron, neodymium, samarium, europium, gadolinium, dysprosium, holmium, erbium, ytterbium, lutetium, iridium, physical mixtures thereof and chemical mixtures thereof.  
     
     
         22 . The method according to  claim 21  where the imaging agent is a metal salt, a metal oxide, an intermetallic, a boride, or mixtures thereof.  
     
     
         23 . The method according to  claim 18  where the article comprises a titanium or a titanium alloy, the facecoat comprises yttria or zirconia, and the imaging agent is gadolinia.  
     
     
         24 . A method for real time detection of inclusions in a metal or metal alloy article, comprising: 
 forming an aqueous or non-aqueous facecoat slurry comprising an inclusion imaging agent;    applying the facecoat slurry to a pattern to form a mold facecoat comprising the imaging agent distributed substantially uniformly throughout in amounts sufficient for imaging inclusions;    serially applying plural backup layers to the pattern to form a mold for investment casting;    casting a metal article using the mold; and    analyzing the article for inclusions using real time N-ray analysis.    
     
     
         25 . The method according to  claim 24  where analyzing further comprises X-ray analysis.  
     
     
         26 . The method according to  claim 24  where the imaging agent includes a material selected from the group consisting of lithium, boron, neodymium, samarium, europium, gadolinium, dysprosium, holmium, erbium, ytterbium, lutetium, iridium, physical mixtures thereof and chemical mixtures thereof.  
     
     
         27 . The method according to  claim 26  where the article comprises a titanium or a titanium alloy and the facecoat further comprises a refractory material selected from the group consisting of yttria, zirconia, alumina, calcia, silica, zircon, titania, tungsten, physical mixtures thereof, and chemical mixtures thereof.  
     
     
         28 . The method according to  claim 24  where at least a portion of the metal or metal alloy article has a thickness of greater than about 2 inches.  
     
     
         29 . The method according to  claim 24  where at least a portion of the metal or metal alloy article has a thickness of greater than about 1 inch, the imaging agent is gadolinia, and alpha case in the article is less than or equal to that when the facecoat is yttria.  
     
     
         30 . A method for real-time detection of inclusions in a titanium or titanium alloy article produced by investment casting, comprising: 
 forming an aqueous or non-aqueous investment casting facecoat slurry comprising an intimate mixture of a mold-forming material selected from the group consisting of yttria, zirconia, alumina, calcia, silica, zircon, titania, tungsten, physical mixtures thereof, and chemical mixtures thereof, and an imaging agent in an amount sufficient to allow imaging of inclusions in the article, the imaging agent including a material selected from the group consisting of lithium, boron, neodymium, samarium, europium, gadolinium, dysprosium, holmium, erbium, ytterbium, lutetium, iridium, physical mixtures thereof and chemical mixtures thereof;    applying the slurry to a pattern to form a mold facecoat comprising the intimate mixture of the mold-forming material and the imaging agent distributed substantially uniformly throughout in amounts sufficient for imaging inclusions wherein a linear attenuation coefficient of the article and a linear attenuation coefficient of the imaging agent are sufficiently different to allow imaging of the inclusion throughout the article by real time N-ray analysis;    serially applying plural backup layers to the pattern and thereafter firing the pattern to form a mold for investment casting;    casting a titanium or titanium alloy article using the mold; and    analyzing the article for mold inclusions by real time N-ray analysis.    
     
     
         31 . The method according to  claim 30  where analyzing further comprises X-ray analysis.  
     
     
         32 . The method according to  claim 30  where at least one backup layer also comprises an imaging agent  
     
     
         33 . The method according to  claim 30  where the mold-forming material is yttria and the imaging agent is gadolinia.  
     
     
         34 . The method according to  claim 30  where the facecoat comprises yttria cocalcined with gadolinia.  
     
     
         35 . The method according to  claim 30  where the facecoat comprises a refractory material and plural imaging agents.  
     
     
         36 . A method for detecting inclusions in investment castings, comprising: 
 placing a solution of at least one imaging agent inside a cavity of an investment casting mold;    allowing the solution to remain in the cavity for a sufficient period of time to infiltrate at least the facecoat of the mold;    removing the solution from the cavity;    casting a metal or metal alloy article using the mold; and    analyzing the article for mold inclusions by N-ray imaging.    
     
     
         37 . The method according to  claim 40  where the imaging agent is selected from the group consisting of lithium, boron, neodymium, samarium, europium, gadolinium, dysprosium, holmium, erbium, ytterbium, lutetium, iridium, physical mixtures thereof and chemical mixtures thereof.  
     
     
         38 . The method according to  claim 36  where the imaging agent comprises gadolinium, the metal or metal alloy is titanium or a titanium alloy, and the facecoat comprises yttria.  
     
     
         39 . The method according to  claim 36  and further comprising analyzing the article for inclusions by X-ray imaging.  
     
     
         40 . The method according to  claim 36  where the solution comprises plural imaging agents.  
     
     
         41 . The method according to  claim 36  and further comprising placing the mold in a chamber and reducing the pressure in the chamber to facilitate solution infiltrating the mold.  
     
     
         42 . A method for detecting inclusions in investment castings, comprising 
 forming an investment casting mold facecoat about a pattern;    infiltrating at least a portion of the facecoat using an aqueous or non-aqueous solution of at least one imaging agent comprising a material selected from the group consisting of lithium, boron, neodymium, indium, samarium, europium, gadolinium, dysprosium, holmium, erbium, ytterbium, lutetium, iridium, physical mixtures thereof and chemical mixtures thereof;    casting a metal or metal alloy article using an investment casting mold having the facecoat; and    analyzing the article for inclusions by N-ray imaging.    
     
     
         43 . The method according to  claim 42  and further including 
 forming plural mold backup layers about the pattern; and  
 infiltrating at least one of the plural mold backup layers with the solution of the imaging agent.  
 
     
     
         44 . The method according to  claim 42  where infiltrating comprises immersing at least a portion of the pattern having the facecoat into an aqueous or non-aqueous solution comprising the imaging agent for a period of time sufficient to infiltrate the facecoat with imaging agent.  
     
     
         45 . The method according to  claim 42  where analyzing the article comprises using moderated neutrons.  
     
     
         46 . The method according to  claim 42  where analyzing comprises real time analysis.  
     
     
         47 . A method for determining whether a metal or metal alloy article has inclusions in real time, comprising: 
 providing a cast metal or metal alloy article made using a casting mold comprising an N-ray imaging agent in an amount sufficient for imaging inclusions; and    determining whether the article has inclusions by real time N-ray imaging using neutrons selected from the group consisting of fast, epithermal, thermal and cold neutrons.    
     
     
         48 . The method according to  claim 47  where the imaging agent comprises an intimate mixture of a refractory material and the imaging agent.  
     
     
         49 . The method according to  claim 47  where the casting mold is infiltrated using solutions of imaging agents.  
     
     
         50 . The method according to  claim 47  where the mold comprises a mold-forming material selected from the group consisting of yttria, zirconia, alumina, calcia, silica, zircon, titania, tungsten, physical mixtures thereof, and chemical mixtures thereof, and the imaging agent is selected from the group consisting of lithium, boron, neodymium, samarium, europium, gadolinium, dysprosium, holmium, erbium, ytterbium, lutetium, iridium, physical mixtures thereof and chemical mixtures thereof.