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Tensile Strength of Ni 45 Al 45 Cr 7.5 Ta 2.5 ‐Coated Sapphire Fibers
Author(s) -
Hajas David E.,
Gebhardt Thomas,
Chen Hao,
Schneider Jochen M.
Publication year - 2008
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.1551-2916.2008.02754.x
Subject(s) - materials science , intermetallic , ultimate tensile strength , composite material , chemical vapor deposition , fiber , sapphire , coating , alloy , compressive strength , laser , physics , optoelectronics , optics
Continuous single‐crystal α‐Al 2 O 3 fibers were coated with Ni 45 Al 45 Cr 7.5 Ta 2.5 (IP75) alloy by physical vapor deposition (PVD). The strength of the coated fibers was evaluated by tensile testing and compared with the strength of uncoated fibers. The effect of temperature during diffusion bonding as well as the presence of a BN interlayer deposited by chemical vapor deposition (CVD) on the fiber strength was studied. Fibers coated with IP75, but without a BN interlayer, retained 23% of their initial strength after the PVD process and fractured during heat treatment. Evidence for thermal stress induced twin formation is presented. Fibers coated with a BN interlayer retained their initial strength during the coating processes. However, only 13% of their initial strength could be retained after the heat treatment. Here, chemical reactions cause morphological changes of the fiber surface. These may act as stress concentration sites, resulting in the extensive strength reduction reported here. These data are important for formulating future strategies avoiding or minimizing strength degradation during production of intermetallic matrix composites.