Accession Number : ADA258027


Title :   Pack Cementation Aluminide Coatings on Superalloys: Codeposition of Cr and Reactive Elements (RE). Technical Report 1. Chromium and Reactive Element(RE)- Modified Aluminide Diffusion Coatings on Superalloys: Environmental Testing. Technical Report 2


Corporate Author : OHIO STATE UNIV COLUMBUS DEPT OF MATERIALS SCIENCE AND ENGINEERING


Personal Author(s) : Rapp, Robert A


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a258027.pdf


Report Date : Nov 1992


Pagination or Media Count : 115


Abstract : A single-step, chloride-activated pack cementation process has been developed for growing a Cr/RE (Y, Zr) -modified or a RE(Y,Zr,Hf)-doped aluminide diffusion coating on commercial Ni-base superalloys. The coatings consisted of an outward-grown, hypostoichiometric B-NiAl layer with a substantial enrichment in Cr and a low reactive element content. The Cr was both dissolved. in the B- NiAl matrix and precipitated as Alpha-Cr second-phase particles. Aluminide coatings grown outwards in a pack permitting powder contact with the substrate were embedded with Al203 and RE oxide pack particles. Physical separation of the substrates from the powder mixture eliminated powder entrapment, but reduced the growth rate and the amount of Cr enrichment in the coating. Isolation of the substrate from the pack introduced partial rate control by gaseous diffusion. Diffusion coating, Aluminizing/Chromizing, Reactive element.


Descriptors :   *ALUMINUM COATINGS , *DEPOSITION , *CEMENTS , *SUPERALLOYS , *CHROMIUM , *DIFFUSION , CONTROL , LAYERS , RATES , SUBSTRATES , PHASE , OXIDES , ALUMINIDES , YTTRIUM , ENRICHMENT , DOPING , NICKEL , ENVIRONMENTAL TESTS , ZIRCONIUM , SEPARATION , CHLORIDES , DIFFUSION COATING , CHROMIZING , PARTICLES , COATINGS , MIXTURES , ALLOYS , REACTIVITIES , ISOLATION , POWDERS


Subject Categories : Inorganic Chemistry
      Coatings, Colorants and Finishes
      Properties of Metals and Alloys


Distribution Statement : APPROVED FOR PUBLIC RELEASE