Developments in the Harmonic Analysis Method for the Nondestructive Determination of Case Depth of Carburized Steel

摘要

The investigation concerned with the nondestructive determination of case depth of carburized steel by the harmonic analysis method was continued. The test method and instrumentation used in this investigation were described in detail in a previous Springfield Armory Technical Report, SA-TR19-1514 (AD-626 602). The harmonic analysis instrument developed previously in the program was utilized to study the effect of sample dimensions, chemical analysis, and the feasibility of employing a probe-type test coil. Results of this investigation demonstrated that the method was effective for measuring deep cases through .075 inch and shallow cases on samples having small cross-sectional areas. The effect of the demagnetizing factor was found to influence only the sensitivity of results, and substantial variations in alloying elements produced only minor differences in harmonic measurements. Correlation between case depth and harmonic phase shift was similar on samples heat-treated by either the gas or liquid-carburizing process. The ability to use a probe-type test coil for measuring case depth by this method was demonstrated by a prototype design. (Author)