Advanced Microstructure Control in the Directed Energy Deposition Process

Robotically integrated gas metal arc welding (GMAW) directed energy deposition (DED) has been garnering much attention for its promise to reduce manufacturing lead times and decrease material buy to fly ratios. In addition this same technology that can be used to manufacture near-net shape components that can be used to modify, construct, and or repair objects in the field. The use of wire feedstock make this technology one of the most promising for expedite deployment to industry as the filler materials or wires are widely available and they have been develop to be deposited by arc welding.

Due to the epitaxial nucleation and competitive growth associated to welding and similar processes, like metal additive manufacturing, a common issue arising in fusion based additive manufacturing is the development of enlarged grain structures with a strong crystallographic texture component aligning parallel to the build direction. This can result in a number of adverse effects including material property anisotropy between the Z & XY axes, decremented static tensile strength, and unexpected ultrasonic waves propagation which can compromise the effectiveness of non-destructive testing for manufacturing and service defects identification and characterization. In addition to the characteristic microstructure and texture, the fast solidification and elevated temperature gradient nature of arc welding develops high residual stress fields which can cause severe distortion, inhibit manufacturability and produce further variation in mechanical and environmental performance.

A number of avenues have shown promise in supporting the production of equiaxed grain structure via the AM process in response to these issues. Some of them include post process heat treatment, alloy modification, nucleating particles addition, hot and cold working, and ultrasonic stimulation of the weld pool.

Industry Sponsor: UNNPP

Faculty: Antonio Ramirez (OSU)

Graduate Students: Jacob Rindler

Industry Contact: Robert Hamlin