PVD DEPOSITION OF HAFNIUM IN ALUMINIDE COATINGS
The paper presents comparison of microstructures of hafnium modified aluminide coatings deposited in two different ways on pure nickel. In the first way a hafnium layer was deposited by the EB-PVD method, subjected to the diffusion treatment for 6 hours and than aluminum was deposited by the CVD method. In the second method, double layers of hafnium (3 μm thick) and aluminum (3 μm thick) were 0 deposited by the EB-PVD method on the nickel substrate. The double layers were subjected to diffusion treatment at 1050 C for 6 h. The obtained coatings were examined by the use of an optical microscope (microstructure and coating thickness) and a scanning electron microscope (chemical composition on the cross-section of the modified aluminide coating). In aluminide coatings deposited by the CVD process, an outward nickel diffusion via the hafnium layer and inward aluminum diffusion to the surface of nickel lead to the formation of a diffusion zone. Hafnium forms a layer of intermatallic phases with nickel in the diffusion zone. Diffusion treatment for 6 h of nickel with hafnium and aluminum layer leads to formation of the Ni5Hf phase.