Fatigue strength of austempered ductile iron-to-steel dissimilar arc-welded joints

• Published in: Welding in the world Vol. 65; no. 4; pp. 667 - 689
• Main Authors: Meneghetti, G., Campagnolo, A., Berto, D., Pullin, E., Masaggia, S.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.04.2021; Springer Nature B.V
• Subjects: Arc welding; Austempered nodular iron; Bending fatigue; Chemistry and Materials Science; Crack initiation; Crack propagation; Design standards; Dissimilar material joining; Dissimilar materials; Dissimilar metals; Fatigue failure; Fatigue strength; Fatigue tests; Fracture mechanics; Fracture surfaces; Materials Science; Metal fatigue; Metallic Materials; Microhardness; Nucleation; Research Paper; Residual stress; Solid Mechanics; Theoretical and Applied Mechanics; Welded joints; Dissimilar welded joints; Arc welding; Fatigue strength; Austempered ductile iron; FAT value
• ISSN: 0043-2288; 1878-6669
• DOI: 10.1007/s40194-020-01058-z

Nowadays, the use of different classes of materials in the same structure is increased to keep pace with innovation and high structural performances. In this context, structural components made of different materials need to be joined together and a possible solution is given by arc welding. Dissimilar welded joints must often be able to withstand fatigue loads; however, Design Standards provide fatigue strength categories only for homogeneous welded joints. The aim of the present paper is to compare the fatigue behaviour of EN-GJS-1050 austempered ductile iron-to-S355J2 steel dissimilar joints to the categories of the corresponding homogeneous steel welded joints, as suggested in International Standards and Recommendations. For this purpose, experimental fatigue tests were performed on a selection of dissimilar welded details. First, the microstructure was identified by metallographic analysis; micro-hardness measurements were collected and residual stress profiles were obtained by using the X-ray diffraction technique on a selection of joints. Misalignments were quantified for all specimens. Then, experimental fatigue tests have been performed on a number of joint geometries subject to axial or bending fatigue loadings and tested in the as-welded conditions. The fracture surfaces of the joints have been analysed to locate fatigue crack nucleation sites.