Spark Plasma Sintering Cladding of Gray Cast Iron with Inconel 625

Cladding of Gray Cast Iron (GCI) components, such as engine blocks and forging dies, is of significant interest due to their high added value. However, material deposition via fusion techniques is problematic due to the formation of brittle phases, porosity generated by CO 2 formation and cracking resulting from thermal stresses. In this context, solid-state cladding presents a promising alternative. This research focuses on the processing of an Inconel 625 clad layer on a GCI substrate via Spark Plasma Sintering (SPS). Samples were processed at 1000 °C and 50 MPa for 10 and 12 min and cooled inside the equipment under vacuum atmosphere. The microstructure and mechanical properties of the cross-section were studied by optical microscopy, SEM, EDS and EBSD analysis, focusing on interface integrity and substrate changes before and after sintering. Vickers hardness tests were performed on the coating and the substrate in the as-received and after processing conditions. Scratch test was conducted at the interface to assess susceptibility to crack propagation. SPS processing reduced the substrate hardness due to an increased ferrite content in the matrix. The Inconel 625 coating exhibited higher hardness than the substrate and very low porosity (< 0.1 area %), indicating good consolidation. The interface proved to be continuous and sound, with minimum porosity, and with the formation of a diffusion layer characteristic of metallurgical bonding. A graphite-depleted diffusion region formed at the interface containing finely distributed NbC, larger Cr 7 C 3 and cementite particles, and acicular ferrite. Scratch tests up to 30 N revealed no cracks or visible delamination at the interface or within the coating. The study demonstrated that the SPS is an effective method for coating gray cast irons, with traditionally poor weldability and high susceptibility to defects, being a robust and reliable alternative method for coating and repairing gray cast iron components.