Development of Production Manufacturing Techniques for Application of Protective Coatings to Thoria Dispersion Strengthened Alloys.

This program was undertaken to develop a low cost manufacturing process for applying a duplex CrAl coating to TD Nickel based on existing coating technology. Several methods of depositing chromium and aluminum were evaluated. These included electroplating, slurry processes and atmospheric pack. The atmospheric pack cementation process was selected as being the most economical and reliable means of depositing the duplex CrAl coating. Other methods such as occluded particle electroplating to deposit a chromium-nickel solid solution layer chromizing exhibited considerable promise but required developmental effort outside the scope of this program. Procedures were developed for producing the duplex coating by atmospheric pack cementation on a scale-up production basis. The atmospheric pack process could repeatedly produce the desired levels of chromium and aluminum. Physical and mechanical properties of coated and uncoated TD Nickel were compared and actual coated TD Nickel engine hardware was engine tested to obtain a comparison between the coating produced in this program and existing commercial coatings. Side-by-side environmental gas turbine engine tests indicated that the performance of the program coating was comparable to commercially available coatings. In addition to a description of the work conducted under this program, a detailed process procedure is supplied which may be used as a base for establishing a commercial production facility.