Structure and mechanical properties of Ti-Si-N coatings

Abstract

In order to better define conditions under which ~{!0~}super-strengthening~{!1~} occurs in the Ti-Si-N system, we performed detailed experimental studies on how the structure and mechanical properties of Ti-Si-N coatings are influenced by the deposition temperature. Different series of Ti-Si-N specimens were prepared in an inductively coupled plasma (ICP)-assisted reactive sputtering system at both low and high temperatures. Coating compositions were measured by Rutherford backscattering spectrometry (RBS) technique, surface roughness was examined on an atomic force microscope (AFM), coating thicknesses were obtained by performing cross-sectional scanning electron microscopy (SEM), and their structure examined with transmission electron microscopy (TEM). Vibrational frequency results from Raman spectroscopy were related to the residual stresses within the coating, which was measured by using a multi-beam optical sensing (MBOS) technique. The extent of phase separation within Ti-Si-N coatings is probed by combining X-ray absorption spectroscopy and TEM. The influence of the extent of phase separation on mechanical properties is probed by instrumented nanoindentation. The nanocomposite structure and hardness of Ti-Si-N coatings were examined as a function of the coating deposition temperature. Models for hardness enhancements in the Ti-Si-N system are discussed in light of the present experimental results. Our experiments showed that the hardness of Ti-Si-N coatings was higher than that of B1-TiN, and that the deposition temperature significantly influences the nanoscale structure and mechanical properties of Ti-Si-N coatings.