Abstract
Dissimilar welds between austenitic and ferritic steels suffer from premature failure driven by interfacial stresses and material degradation brought about by a mismatch in the coefficient of thermal expansion and carbon migration from ferritic steels to the interface, respectively. Trimetallic transition joints using graded composition between ferritic and austenitic alloys are considered a viable pathway to address this issue. However, hot cracking may occur when 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 Grade 22 and SS 316L was designed and fabricated with coaxial powder-blown additive manufacturing using an SS 410-SS 316L grading. After fabrication, the joint was characterized using optical and scanning electron microscopy, wavelength dispersive spectroscopy, as well as electron backscattered and x-ray diffraction techniques. Characterization showed a successful transition joint with minor porosity. The measured composition gradients agreed with the designed composition gradients. This study showed that 12-Cr steels could potentially be used to fabricate transition joints without any hot cracking.
| Original language | English |
|---|---|
| Pages (from-to) | 295S-306S |
| Journal | Welding Journal |
| Volume | 96 |
| Issue number | 8 |
| State | Published - Aug 2017 |
Funding
The authors gratefully acknowledge Electric Power and Research Institute for funding this work. Research at the Manufacturing Demonstration Facili ty, Oak Ridge National Laboratory, was sponsored by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office, under contract DE-AC05-00OR22725 with UT- Battelle LLC. The authors would also like to thank Tom Geer for metallo graphic sample preparation and optical microscopy measurements.
Keywords
- Characterization
- Electron backscatter diffraction
- Graded transition joint
- Laser direct metal deposition
- X-ray diffraction
