Diffusion in Ti/TiC multilayer coatings

The present communication is concerned with the interdiffusion kinetics and the local concentration variations that take place in Ti/TiC multilayer system as a result of thermal anneals between 355 and 550 degreesC. Within this temperature range, carbon is the diffusing species. Carbon diffuses from the carbide layer into the adjacent Ti layers, depleting its concentration within the former and decreasing the width of the latter. Data extracted from diffraction patterns allowed to determine the changes that take place in the relative amount of the two phases as a function of time. By fitting the experimental data to a simple model, we were able to determine the diffusivities of carbon at different temperatures and hence, the activation energy, 132 kJ/moI. This value is significantly lower than expected from extrapolation of data obtained at elevated temperatures and can be attributed to the high defect content of micro-thick multilayers sputter-deposited at low temperature. (C) 2000 Elsevier Science B.V. All rights reserved.