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Open AccessArticle

The Effects of Nitrogen Gas on Microstructural and Mechanical Properties of TIG Welded S32205 Duplex Stainless Steel

1
Faculty of Engineering, Metallurgical and Material Engineering Department, Kırıkkale University, 71450 Kırıkkale, Turkey
2
Faculty of Technology, Metallurgical and Material Engineering Department, Gazi University, 06500 Ankara, Turkey
*
Author to whom correspondence should be addressed.
Metals 2018, 8(4), 226; https://doi.org/10.3390/met8040226
Received: 26 January 2018 / Revised: 19 March 2018 / Accepted: 28 March 2018 / Published: 1 April 2018
Duplex stainless steels are gaining greater interest due to their increasing amounts of application fields. Accordingly, there is a need for awareness of problems associated with improper microstructural distributions such as δ-ferrite (delta-ferrite), austenite and other important intermetallic phases that may form in these steel weldments. Since δ-ferrite versus austenite ratio profoundly influences corrosion and mechanical properties, optimum δ-ferrite ratios must be kept approximately within 35–65 vol % and balance austenite to maintain satisfactory corrosion and mechanical properties on welding of these steels. Cooling rates of welds and alloying elements in base metal are the major factors that determine the final microstructure of these steels. In this work, 3 mm thickness of 2205 duplex stainless-steel plates were TIG (Tungsten Inert Gas) welded with various amounts of nitrogen gas added to argon shielding gas. Specimens were joined within the same welding parameters and cooling conditions. As nitrogen is a potential austenite stabilizer and an interstitial solid solution hardener, the effects of nitrogen on mechanical properties such as hardness profiles, grain sizes and microstructural modifications are investigated thoroughly by changing the welding shielding gas compositions. Increasing the nitrogen content in argon shielding gas also increases the amount of austenitic phase while δ-ferrite ratios decreases. Nitrogen spherodized the grains of austenitic structure much more than observed in δ-ferrite. The strength values of specimens that welded with the addition of nitrogen gas into the argon shielding gas are increased more in both austenitic and delta-ferritic structure as compared to specimens that welded with plain argon shielding gas. The addition of 1 vol % of nitrogen gas into argon shielding gas provided the optimum phase balance of austenite and δ-ferrite in S32205 duplex stainless-steel TIG-welded specimens. View Full-Text
Keywords: duplex stainless steels; TIG welding; nitrogen gas effects duplex stainless steels; TIG welding; nitrogen gas effects
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Başyiğit, A.B.; Kurt, A. The Effects of Nitrogen Gas on Microstructural and Mechanical Properties of TIG Welded S32205 Duplex Stainless Steel. Metals 2018, 8, 226.

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