When a destructive examination of static equipment, piping, etc. cannot be performed, the replica technique offers an interesting solution to perform a metallographic examination in situ.
Replica investigation is a technique to make a print of the material’s microstructure of a prepared surface. To perform this technique the material to be investigated does not need to be removed and stays intact, in contrast to a “normal” metallographic examination. Replica investigation is the most appropriate inspection technique to follow up creep (changes in structure).
Preparation is done by removing the coating or paint layer over a surface of about 10 x 10cm. Thereafter the surface is treated by grinding and polishing until a mirror finish. To visualize the microstructure the material is etched (depending on the material type different chemicals are used). By means of acetate foil and acetone a replica (negative) is made of the prepared surface. Finally this print is studied in the laboratories.