Weldability Evaluation for Alloy Design and Wire Arc Additive Manufacturing of Functionally Graded Materials for Harsh Service Environments

This study sought to evaluate the solidification cracking susceptibility in filler metals designed for wire arc additive manufacturing (WAAM) of a functionally graded pipe component for the harsh service conditions in olefin furnaces. Three filler metals corresponding to the outer diameter (OD), inner diameter (ID), and bulk (Core) regions of the tubular cross-section were developed based on previous computational design work. Cast pin tear testing (CPTT) was performed in this study to rank the solidification crack susceptibility among the three filler metals. CPTT samples were subsequently characterized by scanning electron microscopy (SEM) to propose potential mechanisms for the differences in crack susceptibility observed between the filler metals. Large, blocky Cr-rich carbides forming during solidification were identified as potential bad actors for solidification cracking susceptibility. The nature/amount of liquid ahead of the formation of these carbides was proposed to play a critical role in the difference in crack susceptibility observed among the three filler metals.