PROTECTIE COATINGS FOR ALUMINUM ALLOYS IN A BALLISTIC PROJECTION ENVIRONMENT

ENHANCED GUN TUBES AND PROPELLANT TECHNOLOGY HAVE GREATLY INCREASED PROJECTILE VELOCITIES, DYNAMIC FORCES, AND AERODYNAMIC HEATING OF TANK-LAUNCHED PROJECTILES. IN MANY INSTANCES THE STRENGTH AND TEMPERATURE LIMIATIONS OF ALUMINUM ALLOY FINS HAVE BEEN EXCEEDED UNDER TANK GUN IN-BORE PROJECTION AND IN-FLIGHT CONDITIONS AND HAVE RESULTED IN DEGRADED OR COMPROMISED WEAPON SYSTEM PERFORMANCE. NEW EROSION RESISTANT COATING MATERIALS AND APPLICATION PROCESSES MUST BE DEVELOPED WHICH WILL PERMIT UNCOMPROMISED OPERATION OF HIGH PERFORMANCE LARGE CALIBER TANK-LAUNCHED PROJECTILES WITH ALUMINUM ALLOY FINS, WHETHER FIXED FIN OR FOLDING FIN OR T-TAIL. THESE COATINGS MUST SURVIVE AT THE IN-BORE COMBUSTION GAS TEMPERATURES AND AT THE FREE-FLIGHT RECOVERY TEMPERATURES WITHOUT EVAPORATING, CRACKING, OR SPALLING. PCRL WILL DIAGNOSTICALLY EVALUATE SEVERAL CANDIDATE FIN COATING MATERIALS AND ASSOCIATED APPLICATION TECHNIQUES TO ALUMINUM ALLOY TEST SPECIMENS IN ITS BALLISTIC COMPRESSOR DYNAMIC PRESSURE GENERATING SYSTEM, UP TO TEMPERATURES OF 3000 DEG C AND FLOW VELOCITIES OF 3750 FT/SEC. CANDIDATE COATINGS INCLUDE ZIRCONIUM OXIDE-YTTRIUM OXIDE; GROUP VIII NOBLE METALS (PT, RU, RH); AND SYNTHETIC DIAMOND. WEIGHT LOSS MEASUREMENTS AND PHOTOMICROGRAPHS OF THE COATING SURFACE WILL PROVIDE QUANTITATIVE INFORMATION ON THE EROSION RESISTANCE OF THE CANDIDATE COATINGS.