I. Introduction
The steam generator (SG) tubes are used to transfer the heat generated by the nuclear fission in a primary loop to the turbine in a secondary loop. Metal-loss defects are partly produced in the SG tubes by the stress and heat, because the SG tubes are used under high temperature, high pressure and radioactivity [1], [2]. Tube wall defects, such as corrosion pits, acts as stress raisers, which leads ultimately to rupture [3]. So nickel sleeving is used for protecting the progress of metal-loss defect [4].