Keeping pace with science and technology, radiographic inspection procedures also have been greatly improved and developed for meeting the demands of critical designs/specifications in modern industries. Different from conventional film radiography, Real-Time Radiography and Computed Tomography (CT) have been developed for more critical examination/flaw detection. Real-time radiography, independent of film and other consumable items, provides immediate display of the flaw images on a video screen and hence, is not influenced by too many parameters. The image can be enlarged and the test specimen can be manipulated as desired. Unlike conventional and real-time radiography, CT scan produces cross-sectional views instead of a planar projection. Moreover, underlying and overlying structures do not obscure the CT images. Being highly sensitive CT images are sharper than the radiographs. Further, differing from conventional radiography, Neutron Radiography provides improved contrast on low atomic number materials. Attenuation of neutrons through the material is more related to the specific isotope present than to density or atomic number. Hence, detection of certain light elements in high density materials is of great technological advantage in neutron radiography. Typically, neutrons are highly attenuated by hydrogen, lithium, boron etc. but very less by lead.

The present paper is based on conventional but critical radiographic inspection of investment cast Ni-base superalloy components. It can be seen that conventional radiography with special exposure techniques has been able to serve the purpose by satisfying the minimum requirements of the specification. Detection of defects of the order of 0.25 mm in thin aerofoils by conventional method appeared to be highly challenging. The aerofoils very in thickness and orientation from leading to trailing edge and also from root to the free end. Because of the typical orientation and close placing of the aerofoils on the hub, real-time radiography was considered to be difficult and very costly. In such cases, CT scan could be a perfect QC method. But, it is imperative to mention that the possibility of entrapment of light elements/ ceramic particles in investment cast Ni-base super alloy components indicates more reliable inspection by neutron radiography. Detailed schematic presentation will form the part of the text.