Contrast Enhancement for NDT Images of Turbine Blades by Means of X-ray/Neutron Radiography

Obstruction of turbine blade in different turbines can lead to dangerous accidents, and it is important to check these blades during construction and operation. Due to blockage of air channels, hot spots can lead to blade damage. In this research, X-ray and neutron radiography are used to examine the blades. Reviews of radiographs show that neutrons produce better images, and internal canals and defects are better seen in these images than X-ray images. It is worth emphasizing that neutron radiography with gadolinium tagging can determine the obstruction of blade and evaluate the density of ceramic materials inside the blade. Regarding neutron radiography with film, it can be emphasized that in addition to determining the obstruction of air ducts, the density of ceramic materials inside the ducts can also be evaluated. Also, by tagging with neutron absorbing materials, the contrast of the remaining materials from the ceramic muscle can be increased. Boron, indium and gadolinium can be named as important neutron absorbers. To improve the quality of neutron radiography images, Gadolinium is mainly used as a high neutron absorber. Although the contrast has increased in the reconstructed images, the reconstructed images from neutron radiography still show their superiority in showing the ducts and channel blockages. Different image processing methods can be implemented for the contrast enhancement. In this research, Gaussian convolution method is used to increase the contrast of the radiographs. Although contrast has increased in the reconstructed images by the Gaussian convolution method, the reconstructed images from neutron radiography show the blade structure and its channel blockages accurately. The opinion of radiography specialists also shows that the neutron radiography method gives 60% more information than the X-ray method, and the reconstructed images increased the contrast of the images between 10 to 20%.