Researchers at the International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI) in Hyderabad, an autonomous institute under India’s Department of Science and Technology (DST), have built a crack-free bi-metallic structure joining stainless steel and a nickel-based superalloy through PBF-LB/M additive manufacturing.

The team deposited stainless steel (SS316L) directly onto a surface-ground Inconel 718 (IN718) plate, producing an interface free of visible cracks or porosity. Micro-hardness testing recorded a peak of about 310 HV at the interface, and tensile testing measured an ultimate tensile strength of 550 ± 30 MPa, with failure occurring on the softer stainless steel side rather than at the junction, pointing to a sound bond across the interface.

Combining the toughness and corrosion resistance of stainless steel with the high-temperature strength and creep resistance of nickel-based superalloys in one component addresses a longstanding fabrication problem, according to DST. 

Different zones of a single gas turbine part can be exposed to temperatures near 2000 degrees Celsius alongside far cooler sections, but conventional welding of SS316L to IN718 is complicated by mismatched chemical composition, melting points and thermal expansion, which typically cause solidification cracking, porosity and brittle phases at the joint.

DST reported the process could reduce the amount of costly superalloy needed in a component by confining it to the sections exposed to the highest thermal loads, lowering reliance on imported material.

Uses span aerospace, nuclear and energy sectors

The institute cited boiler tubes and heat exchangers for nuclear and ultra-supercritical (USC) coal-fired plants, along with other energy systems, nuclear reactors, and oil and gas processing equipment, as possible applications where corrosion resistance and high-temperature strength are both needed. 

In aerospace, a bi-metallic part could combine a steel load-bearing section with an Inconel side for heat resistance, while additive manufacturing allows superalloy to be placed only where a part faces extreme thermal exposure, rather than throughout the entire structure.

The research was published in the journal Progress in Additive Manufacturing.