Analysis of stainless steel welded joints: a comparison between destructive and non-destructive techniques

Welding is a joining procedure that offers some benefits over mechanical fasteners such as weight reduction and absence of notches induced by machining operations. Adversely, welding generally involves heating the two parts to be joined, but heating can entail local modifications with loss of material characteristics. The welded zone may also include defects such as gas bubbles, or spurious materials with deleterious effects on the material strength and durability. Thus, each welded joint should be non-destructively tested for quality assurance. In the present work two kinds of joints, lap and butt, are analysed. The joints are obtained from both similar and dissimilar materials, which are plates of AISI304 and AISI430. Two different autogenous (i.e. without filler material) fusion–welding processes are employed, which are the conventional tungsten inert gas (TIG) and the CO2 laser beam. Joints are investigated with destructive and non-destructive techniques to evaluate the presence and the extension of the so-called heat-affected zone and/or the occurrence of defects. Non-destructive evaluation is performed with infrared lockin thermography and results are compared to macrographs and micro-hardness destructive measurements.