Tailoring the mechanical properties of additively manufactured Custom 465 martensitic stainless steel through heat treatment modification

Custom 465 (C465) is a martensitic stainless steel known for its high strength, toughness and corrosion resistance, widely used in aerospace, automotive and medical industries. However, limited work has been conducted on its additive manufacturing (AM) and no dedicated heat treatments have been developed for AM’ed C465 to optimize its strength-ductility trade-off. In this work, the C465 was fabricated via laser powder bed fusion. The effect of hot isostatic pressing, solid solution, cryogenic treatment (-78.5℃) and aging on the composition homogenization, austenite-to-martensite transition, Ni3Ti precipitation were systemically investigated. The APT analysis reveals that Mo atoms accumulate on Ni3Ti precipitate surfaces and inhibits the Ni3Ti growth, contributing to the enhanced strength of C465. The modified heat treatment for AM’ ed C465 reaches comparable tensile strength with the wrought counterpart, yielding an UTS of 1773 MPa, YS of 1686 MPa, and El of 6.5%. A yield strength calculation model was proposed and was validated with measured strength under various heat treatments, providing valuable insight for heat treatment design towards diverse industrial applications.