Fabrication of functionally graded oxides containing superalloy components by additive manufacturing

Functionally graded materials (FGM) belong to a class of advanced materials with properties that progressively vary over one or more dimensions. Since mid-1980, FGM has attracted both research and commercial interest due to its unique gradient and locally optimized material properties, which permits applications in harsh environments with high temperature gradient, wear and corrosion. High-performance heat resistant materials are used for coating high- temperature alloys for next-generation gas turbine engines. Typically, thermal barrier coatings (TBCs) of oxides are applied on the base material to;enhance the operating temperature of the engines. However, after a long-term exposure, the TBC breaks at various points due to high residual stress emanating from the large mis-match between the TBCs and the substrates, which leads to early failure of the substrate material.

It has been observed that functionally graded composites (FGCs) with spatial changes in the composition of the reinforcement and matrix can better accommodate the residual stresses and thermal shock during thermo-mechanical loading. Therefore, FGCs can be a suitable replacement for the thicker TBCs.

Among the;seven fundamental AM processes, laser powder bed fusion (L-PBF) is commonly used for producing metallic composites and requires further;investigation for preparing FGCs. This proposed research work is aimed to develop an innovative in-house developed approach to produce varying volume fraction of oxide dispersions in a given superalloy matrix. Extensive microscopy analysis and mechanical testing will be carried out on the printed FGCs to understand the role of oxide dispersions on the high temperature properties. It is also proposed to print a demonstrator component (gas turbine generator blade) using this approach to carry out in-service testing at the component level.