White Papers

Design, Fabrication, and Characterization of Graded Transition Joints

Source: Welding Journal. August 2017 

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 Inconel­82 alloys by functionally grading them with 316L. Optical and electron microscopy showed extensive cracking in the graded regions. Calculations using Scheil­Gulliver techniques attributed the cracking to the expansion in the solidification range of Inconel­82. To circumvent solidification cracking, another transition joint between SA 508 Grade 22 and SS 316L was designed and fabricated with coaxial powder­blown additive manufacturing using an SS 410­SS 316L grading. After fabrication, the joint was characterized using optical and scanning electron microscopy, wavelength dispersive spectroscopy, as well as electron backscattered and x­ray 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 12­Cr steels could potentially be used to fabricate transition joints without any hot cracking.

Read the Full Paper

Gain Access to these articles by subscribing to the Welding Journal Here!

Leave a Comment