Effect of filler addition on solidification behaviour and hot tensile properties of GTA-welded tube joints of Super 304H austenitic stainless steel

• Published in: International journal of mechanical and materials engineering Vol. 10; no. 1; pp. 1 - 11
• Main Authors: Vinoth Kumar, M., Balasubramanian, V., Gourav Rao, A.
• Format: Journal Article
• Language: English
• Published: Singapore Springer Singapore 01-12-2015; Springer Nature B.V
• Subjects: Austenitic stainless steels; Borocarbides; Copper; Engineering; Gas tungsten arc welding; Mechanical Engineering; Original Article; Oxidation resistance; Structural Materials; Tensile properties; Theoretical and Applied Mechanics; Tube joints; Welded joints; Gas tungsten arc welding; Solidification behaviour; Super 304H; Segregation; Hot tensile properties
• ISSN: 1823-0334; 2198-2791
• DOI: 10.1186/s40712-015-0051-x

Background
Super 304H austenitic stainless steel tubes containing 2.3 to 3 (wt.%) of Cu are mainly used in superheaters and reheaters of ultra super critical boilers due their excellent corrosion and oxidation resistance. Cu addition causes precipitation strengthening effect by fine Cu-rich precipitates which evolve during creep conditions and results in increased creep strength. The microstructural evolution of stainless steels during welding significantly affects the material properties.
Methods
In this work, solidification mode microstructure and hot tensile properties of autogenous and filler-added Super 304H gas tungsten arc (GTA) welded tube joints were correlated.
Results
Autogenous welds of Super 304H solidified as austenite with 1.57 % delta ferrite and intercellular (Fe,Cr)
23
(C,B)
6
borocarbides. In filler-added welds, the higher Ni equivalent and addition of carbide stabilizing elements (Nb,Mo) eliminated δ ferrite and segregation of B as borocarbides.
Conclusions
The filler-added welds exhibited superior tensile strength than autogenous welds at both room and high temperature.