The Fabrication And Properties Of Tantalum Aluminium Nitride Films

TiAlN and TiAl/TiAlN multilayer films with different microstructure and mechanical properties were synthesized on stainless steel(SS) substrate by Filter Cathodic Vacuum Arc (FCVA) technique. The films thickness was tested by AMBIOS Xp-2 profile meter. The microstructure was characterized with X-ray diffraction (XRD). The mechanical properties, such as microhardness, wear resistance and the adhesion strength between films and substrate, were characterized with HXD～1000 microhardness meter, CSEM pin-on-disk wear test apparatus and WS-97 scratch tester respectively. The oxidation resistance was tested by SK2-6-42 opened electrical heated stove. The effect of temperature, bias voltage, N₂ influx and TiAl sublayer on TiAlN microstructure and properties were studied.The characterization results of TiAlN films showed that crystalline FCC-TiAlN was obtained in pre-heated at 350℃while there was amorphous prepared at room temperature (RT), 17.5sccm N₂ influx and -200V DC bias voltage. The microhardness and wear-resistance of TiAlN with FCC microstructure were improved. In addition, films deposited in heating environment had lower coefficient of friction and had better anti-oxidation capability compared to these synthesized at RT because of improvement of microstructure and intensity.At RT, when bias voltage changed from -50V to -200V, microstructure turned to amorphous completely with lower hardness, in spite of improved wear resistance. But at 350℃, Increasing bias voltage from -50V to -100V crystallinity was improved evidently. The film deposited at -100V showed higher hardness and better wear-resistance. No oxidation was observed after 800℃treatment. The change tendency of microstructure and performance with bias were different at different temperature, which depended mainly on the different activity of the ions, and therefore determined the crystal orientation and film properties.Sufficient flow of N₂ is prerequisite condition for forming TiAlN crystal. Amorphous is usually produced when the N₂ gas is insufficient, which lead to low mechanical properties. On the other hand, excessive N₂ gas can be harm to the properties of coating, since the higher the pressure of gas is in the chamber , the lower the atom energy is due to the collision. And which decrease the density of the synthesized film, accordingly, the performances such as wear-resistance and anti-oxidation is decrease.The TiAl intermediate layer between SS substrate and TiAlN film is helpful to improve the adhesion strength of the film. the maximum of 50N was obtained for the film with TiAl intermediate layer, while the adhesion strength of TiAlN film without TiAl intermediate layer is about 20N.