Systems and methods for additive manufacturing and repair of metal components

Abstract

Scanning Laser Epitaxy (SLE) is a layer-by-layer additive manufacturing process that allows for the fabrication of three-dimensional objects with specified microstructure through the controlled melting and re-solidification of a metal powders placed atop a base substrate. SLE can be used to repair single crystal (SX) turbine airfoils, for example, as well as the manufacture functionally graded turbine components. The SLE process is capable of creating equiaxed, directionally solidified, and SX structures. Real-time feedback control schemes based upon an offline model can be used both to create specified defect free microstructures and to improve the repeatability of the process. Control schemes can be used based upon temperature data feedback provided at high frame rate by a thermal imaging camera as well as a melt-pool viewing video microscope. A real-time control scheme can deliver the capability of creating engine ready net shape turbine components from raw powder material.

What is claimed is: 
     
         1 . An adaptive control system for scanning laser epitaxy comprising:
 a thermal imaging camera;   a processor; and   a memory containing instructions that, when executed by the processor, control the processor to:
 control the thermal imaging camera to capture thermal image data of a temperature of a melt pool of a material; 
 estimate a temperature of the melt pool based on at least a portion of the captured thermal image data; and 
 determine a difference of the estimated temperature of the melt pool and a desired temperature. 
   
     
     
         2 . The system of  claim 1  wherein the instructions, when executed by the processor, control the processor to estimate the temperature of the melt pool based on the captured thermal image data and an emissivity of the material. 
     
     
         3 . The system of  claim 1 , wherein the instructions, when executed by the processor, further control the processor to estimate a size of the melt pool from the thermal image data using at least one of Canny edge detection and connected contour labeling. 
     
     
         4 . The system of  claim 1  further comprising a scanning laser configured to create the melt pool of the material. 
     
     
         5 . The system of  claim 4 , wherein the instructions, when executed by the processor, further control the processor to:
 adjust a power of the scanning laser to adjust the estimated temperature of the melt pool toward the desired temperature.   
     
     
         6 . The system of  claim 5  further comprising:
 a machine vision camera, 
 wherein the instructions, when executed by the processor, further control the processor to:
 control the machine vision camera to capture visual image data of the melt pool; 
 estimate a size of the melt pool from at least a portion of the captured visual image data; and 
 adjust a scanning speed of the scanning laser to adjust the size of the melt pool toward a desired size. 
 
 
     
     
         7 . The system of  claim 5  further comprising:
 a machine vision camera, 
 wherein the instructions, when executed by the processor, further control the processor to:
 control the machine vision camera to capture visual image data of the melt pool; 
 estimate a shape of the melt pool from at least a portion of the captured visual image data; and 
 adjust a scanning pattern of the scanning laser to adjust a shape of the melt pool toward a desired shape. 
 
 
     
     
         8 . The system of  claim 6  further comprising:
 a strobe light, 
 wherein the instructions, when executed by the processor, further control the processor to:
 control the strobe light to repeatedly illuminate the melt pool; and 
 control the machine vision camera to capture the visual image data of the melt pool in synchronization with the strobe light. 
 
 
     
     
         9 . The system of  claim 6 , wherein the instructions, when executed by the processor, further control the processor to:
 filter a wavelength corresponding to the laser from the image data to reduce an appearance of the laser within the visual image data; and   estimate the size of the melt pool from the filtered visual image data.   
     
     
         10 . An adaptive control method for scanning laser epitaxy, the method comprising:
 capturing thermal image data of a melt pool of a material created by a scanning laser;   estimating a temperature of the melt pool based on at least a portion of the captured thermal image data; and   adjusting a power of the scanning laser to adjust the temperature of the melt pool toward a desired temperature.   
     
     
         11 . The method of  claim 10  further comprising:
 capturing visual image data of the melt pool; 
 estimating a size of the melt pool from at least a portion of the captured visual image data; and 
 adjusting a scanning speed of the scanning laser to adjust the size of the melt pool toward a desired size. 
 
     
     
         12 . The method of  claim 10  further comprising:
 capturing visual image data of the melt pool; 
 estimating a shape of the melt pool from at least a portion of the captured visual image data; and 
 adjusting a scanning pattern of the scanning laser to adjust a shape of the melt pool toward a desired shape. 
 
     
     
         13 . The method of  claim 10  further comprising:
 estimating the temperature of the melt pool based on the captured thermal image data and an emissivity of the material. 
 
     
     
         14 . The method of  claim 10 , further comprising estimating a size of the melt pool from the thermal image data using at least one of Canny edge detection and connected contour labeling. 
     
     
         15 . The method of  claim 11  further comprising:
 repeatedly illuminating, using a strobe light, the melt pool, 
 wherein the capturing the visual image data comprises capturing the image data of the melt pool in synchronization with the illuminating by the strobe light. 
 
     
     
         16 . The method of  claim 11  further comprising:
 filtering the visual image data to reduce an appearance of the scanning laser from the visual image data; and 
 estimating the size of the melt pool from the filtered visual image data. 
 
     
     
         17 . A system comprising:
 a concentrated energy source configured to selectively melt a material;   an adaptive control system comprising:
 a thermal imaging camera; 
 a processor; and 
 a memory containing instructions that, when executed by the processor, control the processor to:
 control the thermal imaging camera to capture thermal image data of a temperature of a melt pool of the material created by the concentrated energy source; 
 estimate a temperature of the melt pool based on at least a portion of the captured thermal image data; and 
 adjust a power of the concentrated energy source to adjust the temperature of the melt pool toward a desired temperature. 
 
   
     
     
         18 . The system of  claim 17 , wherein the thermal imaging camera is disposed behind the concentrated energy source substantially opposite a scanning direction of the concentrated energy source. 
     
     
         19 . The system of  claim 17 , wherein
 the adaptive control system further comprises a machine vision camera, and   the instructions, when executed by the processor, further control the processor to:
 control the machine vision camera to capture visual image data of the melt pool; 
 estimate a size of the melt pool from at least a portion of the captured visual image data; and 
 adjust a scanning speed of the scanning laser to adjust a size of the melt pool toward a desired size. 
   
     
     
         20 . The system of  claim 19  further comprising:
 a strobe light, 
 wherein the instructions, when executed by the processor, further control the processor to:
 control the strobe light to repeatedly illuminate the melt pool; and 
 control the machine vision camera to capture the visual image data of the melt pool in synchronization with the strobe light.