GRAIN SIZE INSPECTION OF A GAS TURBINE COMPONENT BY X-RAY REFRACTION

1 . A method of inspecting a grain size of a cast alloy component while maintaining the structural integrity of the cast alloy component comprising:

recording a radiographic image of the component;

identifying areas of the component to be inspected;

locating one or more lines having a pre-determined length on the radiographic image at one of the areas to be inspected;

calculating a total number of intersections of grain boundaries with the one or more lines; and

calculating an average grain size.

2 . The method of claim 1 , wherein the cast alloy component is a turbine blade or turbine vane.

3 . The method of claim 2 , wherein the cast alloy component is cast with an equiax grain or directionally-solidified structure.

4 . The method of claim 3 , wherein the areas of the cast alloy component to be inspected are located along an airfoil.

5 . The method of claim 4 , wherein the areas to be inspected along the airfoil are spaced at different radial locations.

6 . The method of claim 1 , wherein the pre-determined length of the one or more lines is approximately 0.5 inches.

7 . The method of claim 1 , wherein the average grain size is calculated based on the ratio of the length of the line to number of intersections.

8 . The method of claim 2 , wherein multiple lines are located within a single radial section of the airfoil.

9 . The method of claim 1 , wherein the method is capable of identifying a chill grain as small as 0.020″ in the cast alloy component.

10 . The method of claim 1 , wherein calculating the number of intersections is determined by an operator upon visual inspection of the radiographic image.

11 . The method of claim 1 , wherein the areas of the component to be inspected are determined by an operator.

12 . A non-destructive radiographic inspection technique for determining a grain size of a gas turbine casting comprising:

identifying inspection areas from a radiographic image of the casting;

locating one or more lines having a pre-determined length on the radiographic image at a radial orientation on the casting; and,

determining a total number of intersections of grain boundaries with the one or more lines;

wherein an average grain size is calculated based on the ratio of line length to total number of intersections.

13 . The inspection technique of claim 12 , wherein the inspection areas are located generally along an airfoil portion of the turbine casting.

14 . The inspection technique of claim 12 , wherein the one or more lines extend a length of approximately 0.5 inches.

15 . The inspection technique of claim 12 , wherein determining the total number of intersections of grain boundaries with the one or more lines is made by an operator.

16 . The inspection technique of claim 12 , wherein the cast alloy is an equiax casting.

17 . A computer readable media for determining a grain size of a cast turbine component comprising:

recording a radiographic image of the component;

identifying areas of the component to be inspected;

locating one or more lines having a pre-determined length on the x-ray image at one of the areas to be inspected;

calculating a total number of intersections of grain boundaries with the one or more lines; and

calculating an average grain size.

18 . The computer-readable media of claim 17 , wherein calculating the average grain size is calculated based on a ratio of line length to total number of intersections.

19 . The computer-readable media of claim 17 , wherein the inspection areas are located generally along an airfoil portion of a turbine casting.

20 . The computer-readable media of claim 17 , wherein calculating the total number of intersections of grain boundaries with the one or more lines requires input from an operator.