The effect of structure and chemistry on the strength of FeCrAl(Y)/sapphire interfaces: II. Strength of interfaces

The interfacial strengths of the FeCrAl/Al2O3 and FeCrAlY/Al2O3 interfaces in both as-deposited and annealed state were measured quantitatively by the laser spallation technique. The results show that in the as-deposited state, the presence of Y significantly improved the interfacial strength from 330 +/- 31 to 686 +/- 36 MPa. However, after annealing the films at 850 degreesC for 16h, the interfacial strength of the Y-free samples increased to 545 +/- 68 MPa, while the interfacial strength of Y-containing sample decreased to 599 +/- 22 MPa. The increase in the interfacial strength of the Y-free films was attributed to an improvement in the crystalline quality of the interface. The decrease in interfacial strength of the annealed Y-containing film in spite of the improvement in the crystalline quality of the interface was attributed to the depletion of Y at the interface due to formation of yttrium oxide precipitates. This is further proved that the presence of Y improves the strength of FeCrAl/Al2O3 interfaces significantly. (C) 2002 Elsevier Science B.V. All rights reserved.