Mechanical behavior of bimetallic stainless steel and gray cast iron repairs via directed energy deposition additive manufacturing
The utility of gray cast iron in engine components remains tied to the mechanical performance and cost. Repair and remanufacturing of castings offer economical and sustainable benefits; however, high thermal input from traditional fusion-based welding is unable to restore the original mechanical quality owing to brittle microstructures and porosity formed in situ. Directed energy deposition (DED) is an additive manufacturing method that has received considerable interest for repairs owing to the highly controllable nature of the process. Despite this, few works have connected the effect of DED parameters on actual interfacial strength. Consequently, distinct DED parameter combinations were identified to maximize the strength and fatigue life of the repaired cast iron. Further, high speed melt pool imaging and residual stress measurements are provided to aid in the understanding of the metallurgical quality and strength seen in these structures. In general, higher scanning speeds and lower thermal gradients promoted comparable tensile strength to that of the original gray cast iron. The results presented here provide a foundation to tune in the DED process to generate the required mechanical quality as a starting point for future process advancements.