Researchers at the International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad, an autonomous institute of the Department of Science and Technology (DST), have developed a breakthrough in manufacturing crack-free bi-metallic structures using laser-based powder bed fusion (PBF-LB/M) additive manufacturing. This technology addresses the challenge of joining stainless steel (SS316L) and nickel-based superalloy (IN718), which are traditionally difficult to weld due to differences in chemical composition, melting temperatures, and thermal expansion coefficients that often lead to solidification cracking, porosity, segregation of Nb/Mo-rich phases, and formation of brittle intermetallics.
The bi-metallic structure was fabricated by building SS316L directly onto a surface-ground IN718 plate using additive manufacturing, resulting in no visible cracks or porosity at the interface. The material demonstrated exceptional mechanical properties with a peak hardness of approximately 310 HV at the interface and an ultimate tensile strength (UTS) of 550 ± 30 MPa. Notably, failure occurred on the softer SS316L side away from the bi-metallic junction, demonstrating superior interfacial integrity.
This development enables the fabrication of multi-material components for demanding industrial environments where different sections experience varying temperature and stress conditions. Potential applications include boiler tubes and heat exchangers for nuclear and ultra-supercritical (USC) coal-fired power plants, advanced energy systems, nuclear reactors, and oil and gas processing industries where corrosion resistance and high-temperature strength are simultaneously required. In aerospace applications, the bi-metallic structure can use steel as the load-bearing component while the Inconel side provides high-temperature resistance. The technology allows strategic placement of superalloys only in regions subjected to extreme thermal exposure, reducing overall use of expensive superalloys and decreasing import dependency.
The research was published in the journal Progress in Additive Manufacturing by researchers S. Narayanaswamy, Gururaj Telasang, Nokeun Park, and Ravi Bathe. The development is particularly significant for India's manufacturing sector as it reduces dependency on imported superalloys while enabling more efficient component design for high-temperature applications across multiple critical industries.