A non-destructive thermographic procedure for the evaluation of heat treatment in Usibor®1500 through the thermal diffusivity measurement

In this work, a laser thermographic method based on the anticorrelation between hardness and thermal diffusivity, to verify the effectiveness of heat treatments in boron steel in a non-destructive way and, also, a procedure to select the best experimental test parameters has been proposed. In particular, a finite element model has been developed and adopted, in conjunction with the response surface method (RSM), to study the resolution of the technique. The error done in the measurement of thermal diffusivity as a function of test parameters has been investigated, obtaining information about the influence of main experimental test parameters: pulse length, acquisition frequency and spatial resolution. Moreover, eight boron steel (Usibor® 1500) plates with different structures (ferritic-pearlitic and 100% martensitic) have been experimentally investigated to validate and verify the proposed method, which has also been verified in comparison with a well-established technique based on the use of a thermal plane source.