The Preparation And Performance Of TiAlON Hard Film

The composite hard films of TiAlON/TiAlN/TiAl and TiAlON/TiAl are depositedon high speed steel substrates by multi arc ion plating (MAIP) technology using thealloy targets of Ti-50Al(at%). The surface composition is controlled by changing thefractional gas flow of reaction gas nitrogen, oxygen. The surface and cross-sectionmorphology, surface composition and composition distribution in cross-section, phasestructure of the two kinds of films are measured and characterized. The hardness of thefilms, the adhesive force between the film and the substrate, and the thermal shockresistance at650℃are tested and analyzed.The results show that TiAlON composite film is consisted of four elements Ti,Al, N, O.With oxygen flow rate decreasing during the test, the oxygen content of thefilm was reduced, and the content ratio of Al/Ti in the film is smaller than which inthe target. X-ray diffraction analysis show that TiAlON composite film is consisted ofTixAlyN、TixAlyand a little of Al or Ti oxide. The films have columnar crystalorganization and there are no defects between the film and substrate obviously. Thethickness of the two kinds of films is about2.0-2.8um and it is found that the thicknessof TiAlON/TiAl composite film is a little lower than TiAlON/TiAlN/TiAlcomposite film.TiAlON/TiAlN/TiAl and TiAlON/TiAl composite film both have a good adhesionbetween film and substrate (adhesive force>200N), superior to TiAlON monolayerfilm and TiAlON/TiAlN double-layer film which are reviewed before.Under the conditions of a certain range oxygen flow, the hardness of TiAlONcomposite film increases by adding oxygen flow at first, and then there exists a sharpdecline in the hardness, it reveals that there is a micro-hardness maxima in that oxygenflow range. And the maxima can reach4000HV extremely, higher than the hardness ofTiAlN monolayer significantly.TiAlON composite film shows a better thermal shock resistance than TiAlN film.The maximum cycle times of TiAlON/TiAlN/TiAl composite film to resist thermalshock at650℃can reach to13-14times, and the number of TiAlON/TiAl composite film is about10-11times. Oxidation, corrosion and abscission on the surface of thefilm are the main failure mode for TiAlON composite film.Based on the mechanical properties comparison between the TiAlON/TiAlN/TiAland TiAlON/TiAl composite film, it is found that the best preparation to get theoptimal mechanical properties of TiAlON/TiAlN/TiAl and TiAlON/TiAl compositefilm, is when the oxygen gas flow reaches to12sccm (partial pressure of oxygen is0.610-1Pa), the bias voltage is150V. And the microhardness of the two kinds ofTiAlON composite film are4163HV and4315HV respectively, the cycle times to resistthe thermal shock are13and10, the adhesive force of the two kinds of films both canreach to200N.