Abstract
Thermochemical analyses were undertaken for a series of pack powder mixtures for depositing aluminide coatings on γ-TiAl by the pack cementation process. Particular attention was focused on the effects of halide activators on the deposition characteristics of the pack powder mixtures. The activators investigated included the halide salts NH4F, NH4Cl, AlF3 and AlCl3. Based on the results of the analyses, a series of coating deposition experiments was carried out to identify optimum pack powder mixtures for depositing adherent and coherent aluminide coatings on γ-TiAl. It was observed that aluminide coatings consisting of an outer TiAl3 layer and an inner TiAl2 layer with a coherent structure free from microcracking could be deposited on γ-TiAl via inward diffusion of aluminium at 1000 ° C using pack powder mixtures containing 4 wt-%Al or less and 2 wt-%AlCl3 with Al2O3 as the inert filler. A discussion is presented on the conditions that need to be carefully controlled to ensure the deposition of aluminide coatings on γ-TiAl with a coherent structure free from microcracking by the pack cementation process. The oxidation resistance and the thermal stability of the aluminide coatings deposited were evaluated in air at temperatures up to 850 ° C. The results are discussed in relation to the oxide scale formation process and the high temperature stability of the diffusion triplet of TiAl3/TiAl2/TiAl.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
