Interfacial Properties of Additively Manufactured M789 Steel on Wrought N709 Alloy

An additively manufactured M789 steel was deposited on wrought precipitation-hardening N709 steel to form a hybrid alloy using the laser powder bed fusion (LPBF) process. After tensile testing, failure in the as-printed (AP) state was detected in the M789 section with a peak strength of 1019 MPa, consistent with the nanoindentation measurement across the M789-N709 interface. The application of heat treatment of the hybrid alloy shifted the failure zone to the N709 alloy with a peak strength of 1600 MPa. The high strength of M789 after heat treatment was due to the formation of the η-phase during aging. A robust metallurgical bond was successfully formed between the two alloys since the fracture did not occur in the interface for both the AP and heat treated (HT) states during tensile testing.