MICROSTRUCTURAL GRADIENTS IN THIN HARD COATINGS - TAILOR-MADE

Microstructural modifications resulting from time dependent variations of the bias voltage during the deposition of thin hard coatings are d iscussed. TiN-coatings are produced by reactive magnetron sputtering i n several modes: (a) stepwise increase of the bias voltage during the deposition, (b) alternating sputtering with and without substrate volt age and (c) pulsed bias voltage. On the basis of X-ray diffraction mea surements, it is demonstrated that residual stress gradients and textu re gradients can be designed tailor-made. Furthermore, results of micr ohardness measurements and scratch tests indicate an improvement of th e mechanical properties, especially for the application of a pulsed bi as voltage. (C) 1997 Elsevier Science S.A.