US Patent 7645485 Chromiumm diffusion coatings

There is provided a method for applying an improved chromium diffusion coating on an industrial item such as a turbine blade of a gas turbine engine. Chromium and other active metals are combined to form an alloy coating. Active elements include silicon, hafnium, zirconium, yttrium, tantalum, and rhenium. For producing the modified coatings through pack cementation chromium and a master alloy are mixed into a packing along with inert material and a halide activator. The packing surrounds a target in a diffusion box. The metals are then deposited by diffusion onto a target surface by pack cementation methods. The diffusion of the desired metals takes place during a coating thermal cycle. Alternatively, the diffusion can take place using an out-of-pack arrangement. Such modified coatings are utilized as improved performance coatings for environmental resistance applications over the current chromium diffusion coatings.