Abstract
Fully austenitic materials, such as nickel base alloys and several stainless steels, can be prone to hot cracking in the heat affected zone during welding. Such cracks, due to their small size commonly denoted as micro-cracks, were found in laser hybrid welds of a high nitrogen stainless steel (UNS S 34565 / German material no. 1.4565). Mechanical testing, such as tensile and Charpy V-notch tests as well as cyclic loading, has been carried out on hot crack afflicted laser plasma hybrid welds. The test results show that the ductility of the material is decreased, whereas the strength is not influenced at all. SEM micrographs of the fracture surfaces revealed that micro-cracks in the HAZ were associated with failure. For a thorough evaluation of the cracking mechanism, the orientation of the micro-cracks alongside the fusion line of the hybrid welds is of great importance. Thus, computer tomography using micro focus X-ray has been carried out. Using this new approach, the orientation of the cracks towards the fusion boundary was ascertained. It turned out that the critical strain emerged at specific sites of the hybrid weld. The critical strain was oriented tangentially to the fusion boundary and perpendicularly to the welding direction. X-ray cone beam computer tomography turned out as a very useful tool for the investigation of the crack distribution and hence, for getting qualitative information about the critical stress/strain distribution in real welds.
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© 2008 Springer-Verlag Berlin Heidelberg
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Stelling, K., Lammers, M., Meinel, D. (2008). Assessment of HAZ Hot Cracking in a High Nitrogen Stainless Steel. In: Böllinghaus, T., Herold, H., Cross, C.E., Lippold, J.C. (eds) Hot Cracking Phenomena in Welds II. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-540-78628-3_18
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DOI: https://doi.org/10.1007/978-3-540-78628-3_18
Publisher Name: Springer, Berlin, Heidelberg
Print ISBN: 978-3-540-78627-6
Online ISBN: 978-3-540-78628-3
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