Investigations on the Diffusion of Platinum between CMSX-4 Superalloy and Platinum-Enriched Bond Coat

Mingwen Bai, Ying Chen, Ping Xiao

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Abstract

The depletion of Pt in Pt-enriched bond coats due to inter-diffusion with superalloys has been a critical concern for the long-term oxidation resistance of thermal barrier coatings. This study investigated the diffusion behaviour of Pt between CMSX-4 superalloys and two commercial Pt-enriched bond coats comprising intermetallic γ′/γ-phase or β-phase, with the aim to understand the mechanism that leads to the depletion of Pt at high temperatures. The results demonstrated that the diffusion of Pt in superalloy disrupts its phase equilibrium, causes a significant lattice parameter misfit between the γ-phase and γ′-phase, and results in the formation of large γ′-grains with irregular shapes and random orientations. In addition, by using the Thermo-Calc software, Pt was found to have negative chemical interactions with both Al and Ta that stabilise Pt by decreasing its chemical activity. The depletion of Al due to the growth of Al2O3 scale during oxidation increases the activity of Pt and therefore accelerates the inwards depletion of Pt towards superalloys
Original languageEnglish
Article number441
Number of pages14
JournalCoatings
Volume11
Issue number4
DOIs
Publication statusPublished - 11 Apr 2021

Bibliographical note

This article is an open access article distributed under the terms and
conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

Keywords

  • Bond coat
  • Diffusion
  • Platinum
  • Thermal barrier coatings
  • Thermodynamic

ASJC Scopus subject areas

  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry

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