Characterization and Performance Evaluation of Pack Cementation and Chemical Vapor Deposition Platinum Aluminide Coatings

Metallurgical evaluation of platinum aluminide coatings applied to industrial gas turbine components, for oxidation and high temperature hot corrosion protection, were conducted. Coatings were processed by electroplating a thin layer of platinum followed by aluminizing using either the pack cementation or the chemical vapor deposition (CVD) processes. Laboratory and field data on the performance of these coatings are presented. Results from these tests showed that both aluminizing processes produced coatings that provided adequate environmental protection. However, the CVD coating experienced less coating growth during engine service and was therefore determined to be thermally more stable than the pack cementation coating in this application.

Simultaneous Chromizing-Aluminizing Coating of Nickel and Nickel-Base Superalloys

ABSTRACTNi and Ni-base alloys have been simultaneously chromized-aluminized by a halide-activated pack cementation coating process. The computer program SOLGASMIX was used to calculate the equilibrium partial pressures of the gaseous species. Chloride-activated packs are predicted to be chromizingaluminizing while fluoride-activated packs are not. Codeposition of Cr and Al occurs in packs containing 90–95 w/o Cr in the masteralloy and either NaCl, CrCl2 or NH4 C1 as the halide salt activator at 1273K.