A novel approach to the production of NiCrAlY bond coat onto IN625 superalloy by selective laser melting

Abstract : The present study investigated for the first time the feasibility of producing by Selective Laser Melting (SLM) a NiCrAlY bond coat material directly onto an IN625 substrate itself produced by SLM. A typical parameters optimization was conducted by varying laser power (P) and scanning speed (v). Single-line scanning tracks and two-layer coatings were carried out and analyzed for 15 different P/v conditions. Several criteria were defined for the selection of appropriate SLM parameters. The results showed significant remelting of the underlying substrate, which is a typical feature of SLM manufacturing. This led to the formation of an intermediate dilution zone characterized by substantial mixing between IN625 superalloy substrate and NiCrAlY bond coat suggesting excellent metallurgical bonding. Optimum processing conditions were found for P =  250 W and v = 800 mm/s. It produced a dense 242 µm thick bond coat including a 36% dilution zone. The SLMed < NiCrAlY-IN625> system exhibited a smooth microhardness profile slightly increasing from 275 Hv in the bond coat to 305 Hv in the substrate. A progressive Al concentration distribution between the phases and low residual stress levels were found in the system. This suggested that SLM might be a valuable alternative manufacturing process for bond coat systems promoting excellent adhesion for high temperature applications.