NANOMETER WEAR MEASUREMENT BY ULTRA-THIN SURFACE LAYER ACTIVATION

SPIRE HAS DEVELOPED A SURFACE LAYER ACTIVATION (SLA) TECHNIQUE FOR MEASURING MATERIAL LOSS DUE TO WEAR, EROSION OR CORROSION TO AN ACCURACY OF .1 MICROMETERS. BECAUSE THE TECHNIQUE IS NONDESTRUCTIVE AND IS EASILY APPLIED IN SITU AND ON-LINE, IT HAS ENJOYED NOTABLE SUCCESS, PARTICULARLY IN SITUATIONS WHERE CONVENTIONAL WEAR MEASUREMENT TECHNIQUES ARE COSTLY OR IMPRACTICAL. THE REMARKABLE ACCURACY OF SLA IS PARTLY LIMITED BY THE FACT THAT THE TECHNIQUE REQUIRES THE USE OF CONVENTIONAL LABORATORY MEASUREMENTS TO DETERMINE A CALIBRATION PROFILE OF THE ACCELERATOR INDUCED ACTIVATION WHICH IS TYPICALLY DISTRIBUTED OVER SEVERAL MICROMETERS. SPIRE PROPOSES TESTING METHODS OF ACTIVATION, WHICH WILL RESTRICT THE ACTIVATION TO AN EXTREMELY SHALLOW, UNIFORM DISTRIBUTION ALLOWING AN IMPROVED ACCURACY OF WEAR MEASUREMENTS. THE ALTERNATIVE METHODS TO BE TESTED INCLUDE DIFFUSION OF TRACER RADIONUCLIDES INTO THE SURFACE, DIFFUSION OR ION IMPLANTATION FOLLOWED BY NEUTRON ACTIVATION OF SURFACE LAYER ELEMENTS, AND USING PARTICLE BEAMS AT OBLIQUE ANGLES. IN ADDITION TO APPLICATIONS OF WEAR MEASUREMENT IN WHICH EXTREME ACCURACY IS REQUIRED, SUCH AS MAGNETIC RECORDING DEVICES, PRECISION GRYOSCOPES, ETC., NANOMETER ACCURACY WOULD ALLOW PRECISE TIMING OF WEAR. FOR EXAMPLE, IF IT IS KNOWN THAT WEAR OCCURS ONLY DURING SOME BRIEF ENGINE TRANSITION PERIOD, THIS WOULD ALLOW THE DETERMINATION OF EXACTLY WHEN DURING OPERATION THE PROBLEM OCCURS. THE METHOD COULD THEREFORE SERVE AS A REAL-TIME DIAGNOSTIC TOOL FOR ENGINEERING AS WELL AS MATERIALS SCIENCE APPLICATIONS.