Vacuum arc deposition of Ni-Ti gradient coatings

The vacuum are discharges in the vapour of the cathode material. When several cathodes are used. the possibility exists to control each discharge independently from the others because no reactive gas is needed which can lead to interaction among the discharges of individual cathodes. The deposition rate of each component can be changed during the deposition process in situ. It permits gradient coatings to be produced. In this work, Ti and Ni were deposited onto silica glass substrates in a chamber having two separated vacuum are sources. The discharge power P for both cathodes was gradually changed during the deposition process. Depth profiling of the coatings produced was made with the aid of secondary ion mass spectroscopy. The concentration of Ni is maximal close to the substrate and decreases gradually towards the surface of the coating. The concentration of Ti is least at the substrate and maximal on the surface. The slope of the concentration profiles depends on the distance L between the substrate and cathodes. The concentration gradient can be controlled both by changing P and L. (C) 1998 Elsevier Science S.A.