Hard coatings deposited by plasma spray can dissipate vibratory energy as well as enhance the ability of turbine components to withstand the environment. However, with no other dissipative mechanism, reducing system quality factors (Q) in bending vibration to a target of 100 while increasing thickness no more than 10% requires a material loss modulus of at least 3.7 GPa (0.54 Mpsi) at strains of interest. Such ceramics as magnesium-aluminate spinel, alumina, titama-alumina, and yttria stabilized zirconia have been found to have loss moduli of only 1 -2 GPa. Preliminary work has shown that vacuum infiltrating alumina with a viscoelastic material (VEM) chosen for effectiveness at about 200F (93C) increased the loss modulus at strains of 400 ppm by a factors of 2 at room temperature and 3 at the design temperature. Infiltration of plasma-sprayed titania-alumina with the same VEM showed increases of factors of 3 and 4, respectively. An infiltrate with a higher glass transition temperature enables high damping at higher temperatures. In current work, particles of high temperature viscoelastic material (HTVEM) are co-sprayed with yttria stabilized zirconia. Preliminary results at low levels of strain suggest that the loss modulus of such materials at 1000-1400F (540-760C) may be as much as four times that obtained with the low temperature infiltrate at 93C.
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