Design, Fabrication, and Characterization of Graded Transition Joints

Journal Article · Tue Aug 01 00:00:00 EDT 2017 · Welding Journal

OSTI ID:1410953

Gandy, David ^[1]; Sridharan, Niyanth ^[2]; Babu, Suresh S. ^[2]; Peter, William H. ^[3]; Leonard, Donovan N. ^[3]; Cakmak, Ercan ^[3]; Dehoff, Ryan R. ^[3]; Jordan, Brian H. ^[3]

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1. Electric Power Research Institute (EPRI), Charlotte, NC (United States)
2. Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Dissimilar welds between austenitic and ferritic steels suffer from premature failure driven by interfacial stresses and material degradation, brought about by mismatch in the co-efficient of thermal expansion and carbon migration from ferritic steels to the interface, respectively. Tri-metallic transition joints using graded composition between ferritic and austenitic alloys are considered as a viable pathway to address this issue. However, hot cracking may occur during welding nickel alloys to stainless steel. This research attempts to reduce the hot cracking susceptibility of Inconel-82 alloys by functionally grading them with 316L. Optical and Electron microscopy showed extensive cracking in the graded regions. Calculations using Scheil-Gulliver techniques attributed the cracking to the expansion in the solidification range of Inconel-82. To circumvent solidification cracking another transition joint between SA 508 Gr 22 and SS-316L has been designed and fabricated with co-axial powder blown additive manufacturing using a SS 410-SS 316L grading. After fabrication, the joint was characterized using optical and scanning electron microscopy, wavelength dispersive spectroscopy, and electron back scattered and x-ray diffraction techniques. Characterization showed a successful transition joint with minor porosity. The measured composition gradients agree with the designed composition gradients. This study shows that 12-Cr steels could potentially be used to fabricate transition joints without any hot cracking.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 1410953
• Journal Information: Welding Journal, Journal Name: Welding Journal Journal Issue: 8 Vol. 96; ISSN 0043-2296
• Publisher: American Welding Society
• Country of Publication: United States
• Language: English

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42 ENGINEERING