Aluminizing, Aluminizing with Yttrium Incorporation and State of art Platinum Aluminizing of Additively Manufactured (AM) Inco 939 Alloy by High Temperature Low Activity (HTLA) Process

Abstract This study aims to establish a laboratory scale out of pack/above the pack diffusion coating system to produce sound aluminide coatings on AM Inco 939 substrates and incorporation of yttrium and platinum to the standard aluminide coatings. Since the introduction of additively manufactured parts into turbine engines have been increased more recently and there are limited investigations about protective coatings upon these alloys, the coatings were produced on Inco 939 SLM (Selective Laser Melting) samples. Successful plain aluminide coatings in terms of aeroengine parts coatings quality standards (growth type, total thickness, additive/IDZ ratio, % at. Al) have been produced in the laboratory conditions via out of pack/above the pack technique. The pack mixture is optimized as %20Al-Cr- %5NHCl and balance Al2O3. The process temperature is fixed as 1100°C during 4 hours and there is no post heat treatment. After aluminization optimization trials, co-deposition of yttrium to the aluminide coatings have been achieved by wt.%2 Y2O3 addition to the source powder mixture. The yttrium precipitates were detected in additive layer close to the interdiffusion zone (IDZ). Platinum aluminide coatings were produced by using previously Pt electroplated specimens and double phase platinum aluminide coatings were resulted. The effect of post heat treatment after platinum plating so called platinium diffusion treatment have been highlighted to eliminate continues PtAl2 layer. To sum up, Inco 939 SLM samples have been successfully coated with standard aluminide, yttrium aluminide and state of art platinium aluminizing techniques and this fills the gap about optimization of coatings on additively manufactured alloys. Turbine engine designers/manufacturers may consider application of these AM 939 alloys to the hot section of prototype engines and receive vaulable feedback from test campaigns.