THERMAL-WAVE IMAGING OF INDENTED DIAMOND-COATED WC

Photothermal radiometry has been used to obtain thermal wave images in the vicinity of indentations in WC-6% Ni coated with chemical vapor d eposited (CVD) diamond. Features in the magnitude and phase of the the rmal signal profile are consistent with a one-dimensional thermal wave theory that assumes (i) an air gap extending well beyond the visibly observable indented region, and (ii) a thermal resistance interface be tween the diamond film and the substrate over the entire coated surfac e. The theory allows us to estimate the air gap thickness, which decre ases as the distance from the indented region increases. Air gap varia tions of tens of nanometers appear to be easily detectable.