INFLUENCE OF N2 FLOW RATE ON STRUCTURES AND MECHANICAL PROPERTIES OF TiSiN COATINGS PREPARED BY HIPIMS METHOD

Over the past years, TiSiN coatings have gained increasing importance in the field of cutting tool coatings due to its enhanced hardness and superior oxidation resistance properties produced by the nanocomposite microstructure of TiN nanocrystals embedded in an amorphous Si3N4 matrix. Many methods have been developed to prepare TiSiN coatings, typically named by the DC magnetron sputtering (DCMS) technique and cathodic arc ion plating (AIP), whereas limited studies have been carried out on the deposition of nanocomposite coatings using the high power impulse magnetron sputtering (HIPIMS) approach. The TiSiN coatings were reactively magnetron sputtered in mixed Ar/N-2 precursor gases in a new BERMS system with different flow rate of N-2 in this work. The deposition rate, crystal structure, composition, surface morphology, microstructure and mechanical properties were investigated systematically by surface profilometer, XRD, XPS, SPM, SEM, HRTEM and nano-indentation and the plasma discharge also was studied. The results show that increasing the flow rate of N-2 caused the decrease of deposition rate as expected, accompanying with the change of preferred orientation from (200) orientation to (220) orientation and the decreased compactness, discharge degree and ionization rate. Contrary to the changes of Ti content, Si content gradually increased with increasing the flow rate of N-2, but their changing scale were small. Combined with XRD and XPS analysis, the results indicated that the coatings were composed of crystalline TiN, amorphous Si3N4 and free Si. Besides, free Si disappeared with further increasing the flow rate of N-2. This nanocomposite structure can ultimately be assessed by HRTEM where individual grains and the amorphous regions can be distinguished. In addition, the grain size increased gradually with increasing the flow rate of N-2. Furthermore, both the hardness and elastic modulus linearly decreased with increasing the flow rate of N-2.