Some Aspects Regarding the Fracture of Welding Joints Applied on Austenitic Steels and INCOLOY Alloys A. RADUTA 1 , M. NICOARA 1 and C. DEMIAN 1 1 “Politehnica” University of Timişoara, Faculty of Mechanics, Department for Material Science and Heat Treatments Bd. Mihai Viteazul nr. 1, 300222 Timişoara, Tel.: +40 256 403651; Fax.: +40 256 403652, e-mail: araduta@eng.upt.ro , mnicoara@eng.upt.ro , cdemian@eng.upt.ro ABSTRACT. Initial material structure, welding parameters as well as subsequent processing or loadings can drastically influence the durability of welded parts fabricated from austenitic steels or super-alloys. Metallographic analysis performed on a considerable number of TIG welded joints between parts fabricated from austenitic steels such as AISI 304, AISI 309, AISI 316 or INCOLOY 800 superalloy allowed identification of different fracture types caused by processing factors: inadequate geometry of the joint, flaws inside the joint or on the heat affected zone (HAZ). Another category of fracture causes is represented by the service conditions such as inter- crystalline corrosion or stress corrosion. The fracture mechanism has been analyzed also as in connection with the processing by mean of cold deformation that was applied after the welding. Some representative examples are presented by mean of metallographic analysis on samples that contained cracks or fractures produced during processing or in service. The analysis procedures, which were applied in different stages of the fabrication route, permitted the identification of specific causes that produced fracture or formation of cracks. INTRODUCTION Austenitic stainless steels are the most used materials for the production of sheathed heating elements, especially for the exterior parts that are required for specific safety conditions. In order to comply with these conditions some the steel has to satisfy several properties, the most relevant being behavior to welding and cold deformation, as well as a very good corrosion resistance inside the working environment [1]. If any of the above mentioned properties is not achieved cracks will occur and the heating element will go out of service as effect of sealing loss. Accordingly to the processing and functioning conditions, the shielding tubes are produced using austenitic stainless steel of the AISI 300 class (16-25 % Cr and 8-20 % Ni), or INCOLOY 800 (18-23 % Cr and 30-35 % Ni), which although is not actually a