Synthesise, Characterization And Properties Of TiSiN Nanocomposite Ceramic Materials

The development of high-speed and dry cutting ofmachine work demands higher hardness and better thermal stability of cutting tools and its protective coatings. TiSiN coating which have been reported possess high hardness, excellent thermal stability and corrosion-resistance has a good application prospect. Howerver, little system work have been focused on the microstructure, properties and applications. In this paper,TiSiN coating and multilayer composite coating are deposited by cathodic arc ion plating in pure N2atomosphere using alloy targets with different silicon content. The microstructure is characterized by SEM, XRD, XPS, TEM, AFM technologies and mechanical properties and friction propertiesare tested by nano-indentation and wear test. The relationships between properties and technical parameters have been discussed. Besides, the effects of multi-layer composite on microstructure and properties have been studied. The high temeperature oxidation resistance, corrosion resistance, and property of resistance to irradiation damage are explored in this paper. The potential applications in high temperature oxidation and corrosionareas are discussed and mechanism of irradiation damage is proposed. In addition,3-D bulk TiSiN has been successfully synthesized by SPS technique. The enhanced mechanisms in microstructure and hardness have been innovative explored.Main conclusions are summarized as follows:(1) Nano-composite TiSiN coatings with high hardness and lower friction coefficient have been successfully synthesized by CAIP technic in pure N2atomsphere by TiSi alloy targets. The N2pressure can greatly influence the chemical composition. As N2pressure increased, orientation of TiN crystalline transferred from (111) to (200) and the grain size decreased. As a result, the hardness and resistor decreased while the friction coefficient increased. The poisoning phenomenon occurred in target when the pressure increased to 2.5Pa. As the Si content in targets increase, the Si content in coating increase and become stable and the orientation of TiN crystalline transferred from (111) to (200). The grain size dually decreases from 18.9nm to 5.6nm and hardness increases to the maximum 40.7GPa as the silicon content in target reach 20 at.%. The studies on TiN/TiSiN multilayer suggest that the interface between the TiN and TiSiN coating can greatly increase the hardness and decrease the friction coefficient. The variation of rotation speed in CAIP technique changes the modulation period of multilayer. As the modulation period decreased, the intensity of (111) increased. The maxium hardness 3413HV and minimium frixtion coefficient 0.49 are observed in TiN/TiSiN coating with a modulation period of 23nm.(2) The friction coefficient and wear rate of TiSiN coatings are lower than that of TiN coating, which increase with the silicon content in target. As silicon content increased, the abrasion mechanism transferred from combination of adhesive abrasion and debris abrasion to debris abrasion. TiSiN coating reveals excellent corrosion resistance which increased with the increase of silicon content. The long time immersion test suggests that the particles and pinholes in surface would be preferred corroded and lead to the xorrosion of interlayer and substrate which results in exfoliation of TiSiN coating. The oxidation experiment in high temperature indicate TiSiN coating aould be applied under 800 "C. The dense amorphous Si3N4 and fine grain retard the diffusion of alloy elements from substrate and O from air and slow down the oxidation process.(3) After irradiation test, amorphization have been obtained in TiSiN coating and lead to decrease in hardness and Young's modulus. The study reveals that the irradiation resistance of TiSiN coating is improved as the grain size decrease. The reason should be related to TiN-Si3N4 boundaries which could promote the recombination of interstitial and vacancies which produced during irradiation. However, an optimization grain size exists.(4) The microstructure of 3-D bulk TiSiN is also nanocrystal TiNsurrounded by amorphous Si3N4. As the Si3N4 content increase, the relative density and grain size decrease while the hardness and Young's modulus increase. But, a critical proportion of Si3N4 exists for the enhanced effects in microstructure and mechanical properties. The enhanced effects in microstructure and mechanical properties are attributed to the amorphous Si3N4 which could retard recombination of TiN grains and dislocation motion. However, increased proportion of Si3N4 leads to a higher temperature for TiSiN to form dense structure. For TiSiN synthesized with fixed temperature, porous structure and decrease in relative density would be observed as the Si3N4 proportion exceeds the critical value, which induced decrease in hardness.