DESIGN AND CHEMICAL VAPOR-DEPOSITION OF GRADED TIN/TIC COATINGS

Gradient materials offer the possibility of tailoring properties between a substrate and a functional surface. Continuously graded coatings based on the Ti-C-N system were designed and synthesized in a computer-controlled, hot-wall chemical vapor deposition (CVD) reactor at 1400 K and a total pressure of 10.7 kPa. In order to define processing parameters, Ti(C,N) monolithic coatings with C/C + N ratios in the range 0-1 were first deposited on a graphite substrate under the same conditions. The C/C + N ratio and the growth rate of the coatings increased with increasing CH4/CH4 + N2 ratio. The compositions of the monolithic coatings determined by X-ray diffraction were found to be between the thermodynamic and the kinetic predictions. These morphological, kinetic and compositional data were used to synthesize graded coatings with linear or exponential concentration profiles. The compositional profiles deduced from Auger line scans were found to be in good agreement with the designed profiles