Effect of Boron Content on Hot Ductility and Hot Cracking Susceptibility in 316L Austenitic Stainless Steel for Welding
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JMEPEG https://doi.org/10.1007/s11665-018-3640-z
Effect of Boron Content on Hot Ductility and Hot Cracking Susceptibility in 316L Austenitic Stainless Steel for Welding Components G. Tran Van, D. Carron, P. Le Masson, V. Robin, A. Andrieu, and J. Stodolna (Submitted November 10, 2017; in revised form June 14, 2018) Liquation cracking may occur in the heat-affected zone during welding. Two factors influence this phenomenon: the tensile stresses generated during welding and the potential loss of ductility due to the presence of a liquid film at grain boundaries depending on their chemical composition. Gleeble hot ductility tests have been used to study the combined effect of boron content and holding time on ductility drop in the liquation temperature range of a 316L type austenitic stainless steel. It is shown that high boron contents and short holding times promote the loss of ductility in this temperature range. Secondary ion mass spectrometry has been used to correlate mechanical results to boron distribution either at grain boundaries or in the bulk. Other welding tests have been performed to confirm the influence of boron content on hot cracking sensitivity of AISI 316L stainless steels. Results indicate that cracks appear on all specimens but at different strain levels. The higher the boron content is, the more the specimen exhibits tendency to hot cracking. Keywords
boron, hot cracking, liquation, stainless steel, welding
1. Introduction Many welded components of pressurized water reactors are made of austenitic stainless steels. During welding of these materials, hot cracking can be encountered due to solidification cracking and/or liquation cracking. The influence of harmful elements such as sulfur, phosphorus, boron, silicon, niobium and titanium on fully austenitic stainless steel cracking sensitivity is well documented (Ref 1-3). With a very low solubility in austenite at high temperature and its tendency to form low-melting eutectics with iron and nickel, boron has a particularly unfavorable influence on hot cracking resistance of austenitic stainless steel (Ref 1, 3) and nickel-based superalloys (Ref 4-7). Even at very low contents, boron favors the phenomenon of heat-affected zone (HAZ) liquation cracking which occurs when both intergranular liquid films and suffi-
This article is an invited submission to JMEP selected from presentations at the Symposium ‘‘Joining,’’ belonging to the Topic ‘‘Processing’’ at the European Congress and Exhibition on Advanced Materials and Processes (EUROMAT 2017), held September 17–22, 2017, in Thessaloniki, Greece, and has been expanded from the original presentation. G. Tran Van, Univ. Bretagne Sud, UMR CNRS 6027, IRDL, rue de Saint-Maude´, 56100 Lorient, France; and EDF – R&D, 6 Quai Watier, 78400 Chatou, France; D. Carron and P. LeMasson, Univ. Bretagne Sud, UMR CNRS 6027, IRDL, rue de Saint-Maude´, 56100 Lorient, France; V. Robin, EDF – R&D, 6 Quai Watier, 78400 Chatou, France; and A. Andrieu and J. Stodolna, EDF – R&D, Site des Renardie`res, 77818 Moret sur Loing, Franc
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