Co-precipitation of M2B on ZrO2 in a Ni-base superalloy with B & Zr additions

Polycrystalline superalloys are high-performance materials with complex microstructures often affected by micro-alloying elements B, C, or Zr added to control mechanical properties during manufacturing and in-service. This requires precise compositional control and makes increasing recycling rates challenging. One example is Zr in scrap used for making Rene ' 41. Zr is incorporated due to comparably higher concentration in Waspaloy commonly mixed with Rene ' 41 scrap. Increasing recycling rates therefore requires a detailed understanding of the impact of Zr on the microstructure of superalloys. High B and High B&Zr variants of the Ni-based superalloy Rene ' 41 are compared using analytical electron microscopy, focused ion beam, and transmission electron mi-croscopy techniques. We show that morphology and dispersion of C16-M2B borides are affected by Zr. C16-M2B, TiC, (Ti,Zr)C, and gamma ' Ni3(Al,Ti) co-precipitate on m-ZrO2. The lattice mismatch between C16-M2B and m-ZrO2 is mitigated with an (012)ZrO2 || (200)M2B orientation relationship allowing epitaxial growth. This demonstrates how the C16-M2B morphology and dispersion is affected by Zr additions in polycrystalline superalloys.