Design, Fabrication, and Characterization of Graded Transition Joints

作者：Sridharan N^*; Cakmak E; Jordan B; Leonard D; Peter W H; Dehoff R R; Gandy D; Babu S S

来源：Welding Journal, 2017, 96(8): 295S-306S.

• Graded Transition Joint
• Laser Direct Metal Deposition
• Characterization
• Electron Backscatter Diffraction
• X-ray Diffraction

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 55 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.

• 出版日期2017-8