Preparation And Properties Of TiSiN Nanocomposite Hard Coatings

TiN is a well established coating material for cutting applications because of itsexcellent wear resistance and corrosion resistance performance. But TiN coatingsexhibit low hardness and poor oxidation resistance performance. The performance of TiNcoatings can be significantly improved by incorporating Si to form TiSiNnanocomposite structure coatings. However, the traditional sputtered TiSiN coatingsgenerally exhibit the loose structure, low adhesion and high deposition temperature, resulting in thelimited wide applications of films. High power impulse magnetron sputtering (HIPIMS) has beendeveloped recently and drawn much attentions due to the high density plasma and high ion energy,which benefits the formation of nanocomposite structure, and thus improves the coatingperformance and lowers depostion temperature. In this study, we investigated the deposition andcharacterization of TiN coatings by a home-made developed HIPIMS method, the effect of ionbormbardment on the deposited TiN coating was systematically studied. In addition, DCmagnetron sputtering (DCMS) was employed to synthesize TiSiN coatings and the filmstructure and properities were comparied with that by HIPIMS. The influence of N2flow rate on theplasma discharge, composition, microstructure and mechanical properties of TiSiN films byHIPIMS were also studied. The results provide us the new strategies and theories to fabricate thehard coatings prepared by HIPIMS technology.The research results indicated that the negative bias voltage has a significant influenceon the structure and properties of TiN coatings during HIPIMS process. TiN coatings exhibiteda trend of densification with the increase of bias voltage from-50to-400V, and thecrystal structure gradually evolved from (111) orientation to (200) orientation. Whenthe bias voltage was-300V, the minimum surface roughness value of10.1nm wasobtained, where the hardness and Young’s modulus of TiN coatings reached to themaximum value of17.4GPa and263.8GPa, respectively. Meanwhile, the highestadhesion of59N was obtained between coating and substrate. The results showed thatthe coatings in case of the fixed substrate holder showed the more dense structure, smoothersurface, higher crystal intensity, improved mechanical properties and corrosion resistance due tothe continued ion bombardment.HIPIMS technology presents the significant advantages in the deposition ofTiSiN nanocomposite coatings. Compared to the coating deposited by DCMS, samples deposited by HIPIMS illustrated a more textured TiN-phase with smallergrains, as well as the smoother and denser morphology. In spite of the lowercompressive stress, the TiSiN deposited by HIPIMS showed the higher hardness of33.21±1.19GPa than that by DCMS at30.09±0.65GPa. Moreover, the adhesion ofwas significantly improved from30N to45N comparing the films deposited byDCMS and HIPIMS. The HIPIMS TiSiN coatings exhibited better tribologicalproperty and corrosion resistance.With different flow rate of N2and the fixed deposition temperature of300℃, it was foundthat the TiSiN coatings by HIPIMS system formed nanocomposites structure, where the TiNnanocrystallines were embedded in an amorphous matrix of Si3N4. Increasing the flow rate of N2caused the decrease of deposition rate as expected, accompanying with the decreased compactness,discharge degree and ionization rate. Contrary to the changes of Ti content, Si content graduallyincreased with increasing the flow rate of N2, but the changing degree was slight. In addition, thepreferred orientation was changed from (200) orientation to (220) orientation and the grain sizeincreased gradually with increasing the flow rate of N2. Both the hardness and elastic modulus ofthe films decreased monotonically with increasing the flow rate of N2.