Developmental Thermal Barrier Coating Bond Coats

Thermomechanical Behavior of Developmental Thermal Barrier Coating Bond Coats

Authors: Amit Pandey 1, 2, Vladimir K. Tolpygo 3,  Kevin J. Hemker 1

1. The Johns Hopkins University, Department of Mechanical Engineering

2. Oak Ridge National Laboratory, Materials Science and Technology Division

3. Honeywell Aerospace, Materials and Process Engineering

 
Abstract

Thermal expansion, microtensile, and stress relaxation
experiments have been performed to contrast and compare the thermal and
mechanical response of two experimental (L1 and H1) coatings provided by
Honeywell Corporation. Thermal expansion experiments
reveal that both coatings have coefficients of thermal expansion (CTE)
that vary with temperature and that the CTE mismatch between the
coatings and superalloy substrate is significant in the case of L1 as
compared to H1. Values of the 0.2% offset yield stress (YS), Young’s
modulus (E), and hardening exponent (n) are reported.
Room-temperature microtensile experiments show higher strain hardening
and a very low value of failure strain for L1 as compared to H1. At
elevated temperatures, there is a significant decrease in the YS of
as-received L1 for (924 MPa at room temperature to 85 MPa at 1000°C) as
compared to H1. Finally, a power law creep description for
high-temperature stress relaxation is developed and the measured values
of the stress exponent (n = 3) and activation energies (Qcreep = 200–250 kJ/mol) are shown to be consistent with power law creep.