Vapor deposition of platinum alloyed nickel aluminide coatings

Platinum-doped NiAl coatings are widely used to increase the oxidation resistance of superalloys. These coatings are usually synthesized by a solid state reaction-diffusion process conducted at high temperature. It requires the chemical vapor deposition of aluminum on a nickel rich superalloy substrate that has been pre-coated with several microns of electrodeposited platinum. Here, we show that an electron beam directed vapor deposition (EB-DVD) technique can be used to deposit well bonded, structurally and chemically homogeneous NiAlPt bond coats of any composition onto superalloy substrates. The approach utilized a high voltage, rapid scan frequency electron beam to independently heat elemental nickel, aluminum and platinum melt pools to create three closely spaced vapor plumes. These vapor plumes were then entrained in an inert gas jet flow, which mixed and directed them to a substrate. By adjusting the electron beam current applied to each elemental source, homogeneous, dense, Pt alloyed β-phase NiAl coatings could be synthesized at substrate temperatures of 1050 °C. The width of the substrate–coating interdiffusion zone was controlled by the deposition temperature and time.