A B C D E F G H I J K L M N O P Q R S T U V W X Y Z All
Aravind, M.
- Study on Effect of Weld Cooling Rate on Fusion Zone Microstructure and Solidification Cracks in 316L Austenitic Stainless Steel
Authors
1 Department of Mechanical Engineering, SSN College of Engineering, Kalavakkam - 603 110, IN
2 Metallurgy and Materials Group, IGCAR, Kalpakkam - 603 102, IN
Source
Indian Welding Journal, Vol 52, No 1 (2019), Pagination: 56-63Abstract
A study on effect of cooling rate on mode of solidification and microstructure was carried out on austenitic stainless steel welds. A tube and plug of 316L stainless steel was joined using Gas Tungsten Arc Welding (GTAW) and laser welding processes. The welds were characterized using optical and Scanning Electron Microscope (SEM). The results indicate that cooling rate of the weld has significant effect on solidification mode, microstructure and solidification cracking. 316L weld joints prepared using GTAW process shows duplex microstructure of vermicular ferrite and austenite in the fusion zone. Whereas, the fusion zone of laser joint shows only single phase austenite microstructure. From these observations, it is clearly understood that the changes observed in the fusion zone microstructures of GTAW and laser welds are due to change in the mode of solidification as a result of change in the weld cooling rates. The predicted mode of solidification for GTA welds for 316L composition used in this study was Austenite-Ferrite (AF) and it was also confirmed through the microstructural observations. In laser joint, the weld has solidified in fully austenitic mode which deviates from the mode of solidification predicted by the conventional constitutional diagrams and hence modified weldability diagram was used. From this investigation, it was also found that the rapid solidification during laser welding is not completely partition less because segregation of sulphur was found using Scanning Electron Microscope – Energy Dispersive Spectroscope (SEM-EDS) along the dendrite boundaries of laser welds. High cooling rate during weld solidification which influences fully austenitic mode of solidification and micro segregation of impurities along the grain boundaries contribute to solidification cracking of welds in laser joints.
Keywords
Solidification Mode, Solidification Cracking, Cooling Rate, Energy Dispersive Spectroscopy, Laser Welding, Gas Tungsten Arc Welding.
References
- Rafal M M, Paradowski K, Brynk T, Ciupinski L, Pakiela Z, Krzysztof J Kurzydlowski (2009); Measurement of mechanical properties in a 316L stainless steel welded joint, Int. Journal of Pressure Vessels snd Piping, (86), pp. 43-47.
- Sarkar R, Chellapandi P, Chetal SC (2012); A design approach for establishing creep strength reduction factor for repaired welds for fast reactor fuel pin end plugs, Nuclear Engineering and Design, (252), pp. 192–200.
- Petretis Br, Balciuniene M (2005); Peculiarities of laser welding of metals. Lithuaniam J Phys, 45(1): pp. 59–69.
- Metals Handbook, Welding, Brazing and Soldering, ASM, 1993. ISBN0-87170-007.
- Kaul R, Ganesh P, Ittoop MO and Nath AK (2002); End Plug Welding of PFBR Fuel tubes with a 2.5 kW CW CO2 Laser, BARC Newsletter, Founder's Day Issue 2002.
- Lienert TJ and Lippold JC (2003); Improved weldability diagram for pulsed laser welded austenitic stainless steels, Science and Technology of welding and joining, pp. 1-9.
- Lippold JC (1994); Solidification Behavior and Cracking Susceptibility of Pulsed Laser Welds in Austenitic Stainless Steels; Welding Research Supplement, pp. 129-139.
- David SA, Vitek JM, Reed RW and Hebble TL (1987); Effect of Rapid Solidification on Stainless Steel Weld Metal Microstructures and Its Implications on Schaeffler Diagram, Welding Research, pp. 289-300.
- Suutala N (1983); Effect of solidification conditions on the solidification mode in austenitic stainless steel, Metallurgical and Materials Transactions, pp. 191-197.