Directed Energy Deposition on Structurally Low-density Substrate and its Effects on Microstructural and Interfacial Bonding Characteristics

This study investigated the deposited materials and interface characteristics exhibited when directed energy deposition (DED) was performed on a structurally low density substrate (SLDS) with a lattice structure. The heat transfer on the substrate during DED was studied for two types of substrates [solid substrate (SS) and SLDS samples]. Temperature-monitoring experiments demonstrated that the SLDS underwent rapid heating (during DED) and cooling (after DED). Therefore, in the transition zone formed in SLDS, excellent fusion occurred at the interface. In addition, the rapid cooling of the SLDS led to a dense microstructure and inhibited the Laves phase. Through bending tests, the adhesion of the deposited interface in relation to the substrate conditions were evaluated. Cracks in SLDS sample penetrated the substrate after crossing the interface, however, they did not propagate along the interface. In contrast, in the SS sample, a crack generated at the surface propagated to the interface, and separation of the deposits from the substrate was observed. This study showed that the SLDS had excellent interface bonding properties.