INVESTIGATION OF THERMAL DIFFUSIVITY-MICROHARDNESS CORRELATION EXTENDED TO SURFACE-NITRURED STEEL USING BOUBAKER POLYNOMIALS EXPANSION

This study sums up the authors recent works(1-6) on steel regarding non-destructive testing and evaluation achieved between 2000 and 2008. The main related items are the establishment of a polynomial correlation(4) between the thermal diffusivity and the Vickers' hardness HV using the recently established Boubaker polynomial expansion. This correlation is undoubtedly an efficient guide to set an NDT protocol to investigate steel-strengthened surface performance. Special attention is given to carburized steel material,(6) as the existence of any appropriated NDT photothermal technique is demonstrated(2,5,6) to be unavoidably subjected to some restrictive conditions. The perspectives of the new features of this recent technique are discussed, with special concern with differently treated material like nitrured and nitrocarburized quenched steel.