Interfacial characterization and bonding performance of additively manufactured GH4169/cast iron bimetal

Bimetal has excellent potential for high-power density cylinder heads due to its design flexibility, functionality, and economy. Interfacial characterization and bonding performance affect the reliability of the bimetal in service. In this paper, the GH4169/cast iron bimetal has been manufactured by the Laser Powder Bed Fusion (L-PBF). The morphology, microstructure, and phases of the GH4169/cast iron bimetallic bonding interface were characterized, and the element distribution was analyzed qualitatively and quantitatively. The nano-hardness and nano-elastic modulus of the GH4169/cast iron bimetallic bonding interface were tested. Shear tests were used to characterize the bonding strength of the GH4169/cast iron bimetallic bonding interface. The results show that the bonding interface of the GH4169/cast iron bimetal is wavy and shows excellent metallurgical bonding. Traces of cyclic flow formed at the bonding interface due to the low energy density and the rapid solidification rate of the molten pool, which prevent the elements from mixing and diffusing sufficiently. As the energy density increases, the traces of cyclic flow at the bonding interface gradually decrease, and the width of the bimetallic diffusion zone (DZ) grows. The bonding of the GH4169/cast iron bimetal is mainly accompanied by the melting and diffusion of Ni, Fe, and C elements to form Ni–Fe compounds, carbides, etc. Spearman correlation analysis reveals that the shear strength shows an apparent positive correlation with the nano-hardness of the DZ, and higher nano-hardness of the DZ improves the bonding strength of the bimetallic bonding interface. The morphology, element distribution, and properties of the bonding interface are all factors that affect the bonding performance. This study can provide data support and a theoretical basis for applying the GH4169/cast iron bimetal from the material to the structural level.