Microstructural evolution of TiC/a-C nanocomposite coatings with pulsed magnetron sputtering

The microstructure and property of magnetron Sputtered coatings are strongly affected by the intensity of concurrent ion impingement, in particular, by the energy distribution of impinging ions and the flux ratio between impinging ions and depositing atoms. In this paper, we report some striking results in the microstructure manipulation and residual stress control of TiC/a-C nanocomposite coatings with pulsed-DC magnetron sputtering. Ion mass/energy spectrometry of plasma diagnostics reveals that, depending on the waveform, frequency and width of pulses, pulsing the magnetrons can control the flux and energy distribution of Ar+ ions over a very broad range, in comparison with DC Sputtering. The latter delivers only low energy Ar+ ions and also less flux. With increasing pulse frequency, the nanocomposite coatings exhibit evolutions in the morphology of growing interface from rough to smooth and in the microstructure from strongly columnar to non-columnar. AFM, SEM, HR-TEM and nanoindentation are employed to characterize the deposited coatings, supported with plasma diagnostic experiments for a better understanding of the pulsed sputtering process.