Induction thermography as an alternative to conventional NDT methods for forged parts

Abstract

Dye penetrant inspection and magnetic particle inspection are widely used in industry, to inspect metallic components. These non-destructive testing methods are highly efficient but they induce possible risks for operators’ health (use of chemicals, exposure to solvent vapors and to electromagnetic fields, etc.) and for the environment (generation of effluents, significant energy consumption for drying or magnetization operations, etc.). As they are faced with tougher environmental rules, increasing numbers of manufacturers take a real interest in environmentally-friendly alternative inspection methods capable of giving similar results. CETIM, the French technical center for the mechanical industry, has been involved in the development of active infrared thermography for several years, especially induction thermography on forged components. After tests on a car ball joint previously published, we will present a comparison between induction thermography and magnetic particle inspection on a batch of 26 cracked wheel hubs. Destructive metallographic analyses confirm that induction thermography is able to reveal more defects which are invisible to the naked eye than magnetic particle inspection, yet considered as the reference method. A second application of induction thermography will be presented on non-magnetic components. Tests results on artificial hip joints made of titanium, austenitic steel and cobalt-based alloy will be presented in comparison with dye penetrant inspection results. Finally, the advantages and drawbacks of induction thermography will be discussed compared to those of magnetic particle inspection and dye penetrant inspection.