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This paper deals with the development and characterisation of functionally graded MoNiCr-316L materials manufactured by directed energy deposition with laser beam and wire feedstock (DED-LB/W). The work verifies the feasibility of joining a nickel-based MoNiCr alloy, developed by COMTES FHT a.s. for high-temperature molten-salt applications, with austenitic stainless steel 316L. Cubic blocks of 20 mm x 20 mm x 20 mm were produced in two deposition sequences: MoNiCr deposited on 316L and 316L deposited on MoNiCr. The samples were evaluated in the as-built state and after heat treatment at 1100 °C and 1200 °C, as well as after hot isostatic pressing at 1200 °C and 150 MPa. The interface was assessed by metallography, EDS line analysis and HV1 hardness profiling. The results show that the deposition sequence has a decisive effect on interface morphology. Deposition of MoNiCr on 316L produced a sharply defined transition, whereas deposition of 316L on MoNiCr resulted in a wider mixed zone. This behaviour is attributed to the lower solidus and liquidus temperatures of MoNiCr and to local remelting during subsequent deposition. Heat treatment and HIP promoted recrystallisation and reduced hardness gradients across the interface. The results confirm that DED-LB/W enables stable MoNiCr-316L multimaterial structures with an interface that can be tailored by deposition order and post-processing.
Keywords: Functionally graded materials, MoNiCr nickel alloy, 316L stainless steel, DED-LB/W, heat treatment© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.