Multi-layered of IN625 cladding by DED on the AISI 304: metallurgical and mechanical approach

This study investigates the effect of cladding thickness, controlled by increasing the number of deposited layers, on the microstructural and mechanical behavior of IN625 cladding deposited on AISI304 stainless steel using the Directed Energy Deposition (DED) process. The observed microstructural evolution and localized refinement in the cladded region are believed to contribute to the improvement in mechanical behavior. The average microhardness of the cladded region increased from 234 HV in the thinnest specimen to 270 HV in the thickest specimen, while the overall hardness of the clad/substrate system decreased from 482 H.B. to 438 H.B. due to reduction in hardness gradient across the interface. Residual stress measurements revealed that thinner cladded specimens experienced higher internal stresses because of steep thermal gradients, whereas thicker multilayer deposits promoted stress relaxation and improved thermal distribution. The highest shear strength was obtained for the specimen with approximately 4100 μm cladding thickness, reaching 812.24 MPa at room temperature, accompanied by dominant ductile fracture behavior. In contrast, specimens with 2000 μm and 9711 μm thickness exhibited interfacial failure associated with void formation and delamination near the interface. Fractography confirmed strong metallurgical bonding in optimized conditions, with failure occurring predominantly in the substrate. These findings demonstrate the critical role of deposition thickness and process optimization in improving interfacial integrity and mechanical performance of DED-fabricated SS304-IN625 cladding systems.