Microstructure and mechanical properties of Ni-based superalloy foil with nanocrystalline surface layer produced by EB-PVD

Abstract

0.15 mm thick Ni-based superalloy foil with a nanocrystalline (NC) surface layer was produced via electron beam physical vapor deposition (EB-PVD) technique. The microstructure evolution of the Ni-based superalloy foil was characterised by using SEM, XRD and TEM analysis. Three-point bending tests were carried out on two sides of the Ni-based superalloy foil. Tensile test was examined at room temperature. The results indicated that three microstructural zones, i.e. the nanocrystalline (NC) surface layer, the transitional zone and the coarse-grained CG zone, were discernible. The grain size changed gradually from ∼40 nm in the NC surface layer to ∼4 μm in the CG zone due to the different distribution of Y 2O 3. Three-point bending tests resulted in different fracture characteristics for NC surface layer and CG zone. The fracture of the NC surface layer with many parallel cracks near the fracture showed plastic behavior. However, the brittle fracture was a typical characteristic of the CG zone and only a few of micro-cracks can be observed.