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Multifunctional Reaction‐Bonded Alumina Coatings for Porous Continuous Fiber‐Reinforced Oxide Composites
Author(s) -
Mechnich Peter,
Braue Wolfgang,
Schneider Hartmut
Publication year - 2004
Publication title -
international journal of applied ceramic technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.4
H-Index - 57
eISSN - 1744-7402
pISSN - 1546-542X
DOI - 10.1111/j.1744-7402.2004.tb00185.x
Subject(s) - materials science , composite material , porosity , thermal shock , ceramic , ceramic matrix composite , oxide , composite number , thermal stability , chemical engineering , metallurgy , engineering
Highly porous, alumina‐based ceramic matrix composites (CMCs), without additional fiber‐matrix interphase, display excellent high‐temperature stability, damage tolerance, and thermal shock resistance. However, the very high gas permeability and the rough CMC surface associated with the winding pattern may give rise to problems in a variety of applications. The solution for these problems is the application of additional functional coatings based on reaction‐bonded alumina (RBAO). RBAO topcoats for porous alumina‐based CMCs were fabricated by a simple painting and firing process. The RBAO topcoats display excellent adherence and provide smoothing and stabilization of the surface and, hence, protection against erosion and wear. The pore structure of the RBAO coats particularly depends on the RBAO starting materials. The gas permeability of RBAO coated CMCs is reduced by several orders of magnitude with respect to uncoated CMCs if optimized ratios between Al and Al 2 O 3 in the RBAO starting compositions are employed. The RBAO coatings also work as suitable bond‐coats for additional plasma‐sprayed environmental barrier coatings.