Translated Abstract
The research direction of this thesis is pertain to the surface engineering. Surface engineering is a system engineering that includes surface coating, surface modification, or surface hybrid treatments. The purpose is to change the morphology, chemical composition, structure and stress condition of metal or non-metal surfaces that could obtain the required performance. As the most important branch of surface engineering, hard coating has been widely used in many domains include mechanical processing, mold manufacture, anti-friction, anti-corrosion and so on. However, with the rapid development of industrial technology, the complexity and diversity of service environment has brought many new requirements, such as super high temperature resistance, super hard, super anti-friction, super anti-corrosion etc. In this thesis, we have developed a series of multilayer coatings for the requirments of precision machining, die making and corrosion protection. The main work is as follows:
During the machining process of high-temperature component of aircraft engine, the service environment of cutting tools is very harsh, the selected coatings must be high toughness, high hardness, high temperature resistance, high oxidation resistance, and many other properties. A lot of studies show that the hard coating with nanoscale multilayer structure has superior mechanical properties. On this basis, we first proposed depositing multilayer structure hard coatings using multi arc ion plating technical, both the sub-layers (TiAlN coating and ZrN coating) show high toughness and high temperature resistance. The sample which showed the best comprehensive performance was composed of a symmetrical multilayer structure (modulation ratio of 1:1). The analytic results show that the TiAlN/ZrN multilayer coating not only has the superhard effect that arised from nanometer multilayer structure, also integrates the toughness of the two sub-layers. Most importantly, it raises the service temperature to 850 ℃ or even higher, that is 50 ℃ higher than TiAlN single layer coating and 100 ℃ higher than ZrN single layer coating respectively, and that greatly improves the service life of the cutting tools.
Based on the studying of the effect of the gas flow ratio (N2:CH4) on the wear-resistace property of TiAlCxN1-x single layer coatings, a series of TiAlN/TiAlC0.37N0.63 nanoscale multilayer coatings were designed for responsing to the request of tools and moulds in wear-resisting. During the deposition process of TiAlC0.37N0.63 sub-layer, the working gas is a mixture of Ar(12 sccm), N2(35sccm) and CH4(35sccm), and the single layer structure TiAlC0.37N0.63 coating has high content of hard phase (Ti-C, 18.2%), the highest content of lubrication phase (graphite, 6.8%), the optimal adhesive strength (~53 N), the lowest coefficient of friction (COF=0.53) and the highest factor of H3/E2 (0.63). For the multilayer coatings, when the modulation ratio is 1:1 the highest hardness (thickness:3.5 μm, HV0.10=2793) and lowest friction coefficient (COF=0.46) were obtained, and its comprehensive performance is greatly superior than any single-layer structure coatings.
As one of the most important metal structure materials, 304 stainless steel has been widely used in many fields. However, when served in an environment, in which the content of chloride ion is above 25 ppm, the stress corrosion, pore erosion and intergranular corrosion would occurred inside the 304 SS. However, the chloride ion is widely distributed in body fluids, seawater and soil. To further expand the application areas of 304 stainless steel, a corrosion-resistant oxide (ZrO2) coating were deposited using multi arc ion plating. On this basis, a super corrosion-resistant ZrN/ZrO2 multilayer coating were deposited on the surface of 304 SS. The corrosion resistance of the samples were characterized in hydrochloric acid solution with potentiodynamic polarization method, the results show that the multilayered ZrN/ZrO2 coating not only has an excellent adhesive strength and high toughness, but also, it can be used as protective coating for 304 stainless steel to resist the erosion of various solutions including 3.5 wt % NaCl, 10 wt % HCl and 20 wt % HCl, which greatly expanded the application fields of 304 stainless steel.
Translated Keyword
[Multi Arc Ion Plating, Multilayer Coatings, TiAlN, ZrN, ZrO2]
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