Damping Coatings for Gas Turbine Compression System Airfoils

The use of monolithic airfoil structures in static and rotating components such as one-piece integrally bladed rotors (IBR''s) in military turbine engines has created an increased risk of high cycle fatigue(HCF). The Phase I and Phase II SBIR efforts demonstrated that plasma sprayed ceramic coatings infiltrated with viscoelastic (VEM) polymers exhibited over six times the damping of typical plasma sprayed damping coatings at low dynamic strains and close to twice the damping at higher strains. Elevated temperature (200 to 400°F) spin pit and fatigue tests were conducted with no indication of macro creep of the VEM. It was observed that there was about a 10% decrease in the fatigue strength of the coated specimens as compared to the bare specimens. However, due to the increase in damping it is believed that this is very acceptable. The Phase II expansion research studies will allow for improvements to the plasma spray coating cell, continued plasma spraying studies to optimize coating process, the development of application methods necessary to apply the plasma sprayed damping coatings to a variety of aircraft engine airfoil configurations, and the evaluation of optimized plasma sprayed damping coatings on airfoils and blisks to determine the coating parameters, such as coating thickness, location, and surface finish to satisfactorily provide the necessary damping,engine performance and structural durability.