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Strength Degradation and Failure Mechanisms of Electron‐Beam Physical‐Vapor‐Deposited Thermal Barrier Coatings
Author(s) -
Ruud James A.,
Bartz Andi,
Borom Marcus P.,
Johnson Curtis A.
Publication year - 2001
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.2001.tb00875.x
Subject(s) - materials science , thermal barrier coating , yttria stabilized zirconia , composite material , delamination (geology) , electron beam physical vapor deposition , yttrium , fracture toughness , coating , physical vapor deposition , cubic zirconia , degradation (telecommunications) , temperature cycling , chemical vapor deposition , metallurgy , thermal , oxide , ceramic , paleontology , telecommunications , tectonics , physics , optoelectronics , meteorology , biology , computer science , subduction
Failure mechanisms were determined for electron‐beam physical‐vapor‐deposited thermal barrier coating (TBC) systems from the degradation of mechanical properties and microstructural changes in a furnace cycle test. Bond strength degradation for TBCs resulted from the initiation and growth of interfacial delamination defects between the yttria‐stabilized zirconia topcoat and the thermally grown alumina (TGO). It is proposed that defects started from concave depressions in the bondcoat surface created by the grit‐blast‐cleaning process and that defect growth was driven by the reduction in compressive strain in the TGO as the alumina deformed into and displaced the bondcoat during the cooling cycles. Inclusion of yttrium in the substrate resulted in a doubling of the furnace cycle life of the TBCs because of enhanced fracture toughness of the TGO‐bondcoat interface.