Dynamic mechanical properties of ZrO2/NiCoCrA1Y composite coatings

The dynamic mechanical analyzer (DMA) was utilized systematically to invest igate the temperature dependence of the dynamic mechanical properties of as -sprayed ZrO2/NiCoCrAlY composite coatings. The dynamic storage modulus of graded coatings varied in a graded and linear manner from 30-400 degrees C. An increase of modulus was observed for the 100 wt.% NiCoCrAlY and graded coatings at 400-650 degrees C, while 100 wt.% ZrO2 coating exhibited linear behavior from 30-900 degrees C. This stress-induced and thermally activate d structural relaxation of the coatings at 400-650 degrees C was attributed to the amorphous-to-crystalline transition of NiCoCrAlY phase. The relaxat ion effect responsible for the modulus increase is the diffusion of nickel atoms with activation energy of 248.3 kJ/mol and a frequency factor of 5.9 x 10(16) s(-1). (C) 2000 Elsevier Science S.A. All rights reserved.