Ni3Al and Ni3Si-based intermetallics produced by the Osprey process

Abstract

Four NiAlbased and two NiSiTibased intermetallic compounds were spray-deposited using a nitrogen gas for atomization. The impurity contents, relative densities and microstructures of the alloys were investigated in the as-deposited condition.The oxygen content of the alloys varied from 20 to 90 ppm, and the nitrogen content ranged from 10 ppm in a binary Ni 3 AI compound to 90 ppm in NiAlCrFe alloy and to 150 ppm in the case of NiSiTi. No sign of nitrides or oxides was observed. The relative density of the alloys was higher than 99% and the majority of pores located at grain boundaries. The chromium free NiAI alloy had a single-phase, equiaxed and recrystallized structure (γ′), while the chromium containing NiAI alloys had a γ γ′ multiphase structure with 5–20% volume fraction of the disordered γ phase. The γ phase formed a network or a bimodal mixture of network and lamellar structures in the ordered γ′ matrix. The NiSiTi alloys showed a cell structure with cell interiors consisting of γ γ′ network structure and cell borders of the ordered γ′ phase. The mechanical properties were comparable with those of the previously spray-deposited Ni 3 Al-based alloys or with those of the NiSiTi based alloys of the present type.