IN-SITU FORMATION OF Ni-Cr-Al-R. E. ALLOY BY LASER CLADDING WITH MIXED POWDER FEED.

Oxidation resistant materials for service at elevated temperatures must satisfy two requirements: diffusion through oxide scale must occur at the lowest possible rate and oxide scale must resist spallation. The formation of an Al//2O//3 protective scale fulfills the former requirements but its adherence is poor. Rare earths such as Y or Hf are added to improve adhesion. In this paper, in situ Ni-Cr-Al-Hf alloy has been developed by laser surface cladding with mixed powder feed. A 10 kW CO//2 laser was used for laser cladding. Optical, SEM, and STEM microanalysis techniques were employed to characterize the different phases produced during laser cladding process. Microstructural studies showed a high degree of grain refinement, increased solid solubility of Hf in matrix and Hf rich precipitates. The paper deals with the microstructural development during laser cladding process.