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Improved mechanical performance and structural properties of bias induced reactively sputtered Si doped TiAlC nanocomposite coatings
No full textSi doped TiAlC nanocomposite coatings consisting of nanocrystallineTiC phase embedded in amorphous matrix of a-C/a-Si/a-Al4C3 have been deposited on stainless steel and silicon (100) substrates using four cathode reactive unbalanced direct current magnetron sputtering at Tsub= 300οC. The effects of substrate bias ǀVbǀon the microstructure, surface morphological, compositional, mechanical and frictional properties have been carried out by using X-ray diffraction (XRD), field-emission scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, nanoindentation hardness tester and nano-scratch measurements. XRD analysis reveals that the coating exhibits fccNaCl type TiC (111) preferential orientations. Moreover, micro-Raman spectroscopy study indicates the existence of graphitic rich layer of a-C in the coating as the bias voltage increases. Substrate bias causes a subsequent change in the microstructure from fine granular to a denser morphology. High rate of ion bombardment induces a transformation from columnar to a non-columnar microstructure as the bias voltage increases. Coatings prepared at an optimum ǀVbǀ=50 V, exhibit the excellent hardness and Young’ modulus value of ~ 33 and 280 GPa, respectively. The friction co-efficient measurements show a decrease from ~ 0.55 to 0.24 as the bias voltage increases from ǀVbǀ= 25 to 150 V