STRESSES IN SPUTTER DEPOSITED THICK COATINGS OF CHROMIUM AND ZIRCONIUM DIBORIDE ON POLYMERIC COMPOSITES

Moldable fiber impregnated composites are currently used to fabricate high temperature radomes, compressor vanes, and other structural parts for aerospace applications. When severe erosion and dust type environments are encountered, surface protection in the form of a hard erosion resistant coating is required. The purpose of this work is to estimate the total induced stress in chromium and zirconium diboride coatings deposited on fiber impregnated polyimide composites by magnetically enhanced direct-current (dc) sputtering. Process variables were sputtering pressure, power density, and coating thickness. Estimates of the various stress components were obtained using the bending-beam method where stress is calculated from the deflection of the composite beam formed by the combination of the substrate and coatings. The equivalent stiffness (EI) method was used to determine the relationship between the estimated stress components and the coating deposition parameters. It was observed that the coatings were in compression and the magnitude of the compressive stress was greatest in coatings deposited in an argon partial pressure of 2.0 mTorr. Compressive stress was found to increase with increased power density and coating thickness. © 1990, American Vacuum Society. All rights reserved.