Enhancing mechanical properties and creep performance of 304H and inconel 617 superalloy dissimilar welds for Advanced Ultra Super Critical power plants

This investigation is conducted to find improvements in the mechanical properties of the dissimilar welds between austenitic stainless steel and Nickel superalloy used in the manufacturing of Advanced Ultra Super Critical (AUSC) power plants boiler components. Nickel superalloys (IN617) have excellent creep rupture properties, so they are employed in higher temperature regions (above 700 ◦C) of the boiler. In contrast, austenitic stainless steel (304H) is used in moderate temperature regions (up to 650 ◦C) part of the boiler, also striking off the economic balance need. The welding is carried out with manual multipass Gas Tungsten Arc Welding using an IN617 filler to compare 304H and IN617 weld without and with a buttering layer. Multiple attenuated buttering material layers are deposited at the 304H side, further machining the butter weld layer to the weld groove and closure weld to the IN617 part. The buttering technique improves mechanical properties and high-temperature creep rupture life through microstructure transformation. The dissimilar weld characterization shows a supplementary dendritic growth layer for the buttering deposition. The tensile strength is found to be 728.214 MPa with buttering higher than without buttering weld (620.25 MPa). The V-notch Charpy impact toughness value of the buttered weld sample is 66 J, greater than the non-buttered sample, i.e., 63.25 J. The creep rupture duration significantly increased with buttering. Strain hardening at higher applied stress helps to resist creep failure even at higher temperatures.

Publication year:2023

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