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Adhesive wear is one of the major reasons for short tool life during machining titanium alloys. This study presents a new kind of low adhesive wear TaO functional coating prepared by magnetron sputtering. The composite coating is composed by two layers of a solid solution TiAlTaN in bottom and a TaO (Ta 2 O 5 or TaO x ) on top. Tool life of the TiAlTaN/TaO coatings is increased more than triple the TiAlTaN single coating by titanium cutting experiments. Cutting performance of commercial TiAlN-based coated tool is increased 267% after coating the TaO on the surface. Friction and wear between the coatings and Ti6Al4V counterpart have been conducted. The results show that both the friction coefficient of the coatings (from 1.05 to 0.82) and surface roughness (from 12.2 ± 0.6 to 7.1 ± 0.1 nm) are decreased by increasing TaO thickness from 0 to 150 nm. The adhesive bonds between coating and titanium also reduce with increasing the TaO thickness. This leads to the significantly reduction of the adhesion at the cutting tool tip after coated the TaO coating. This is because that the titanium is not easy to bind with the TaO coating by the calculated positive interaction energy between the Ta 2 O 5 surface and pure Ti. [ABSTRACT FROM AUTHOR]

Research on the relationship of microstructure and properties of coated tools such as TiAlN and TiAlSiN plays a key role in obtaining the needed cutting performance in titanium machining. In this study, three kinds of coatings of TiAlN, TiAlSiN monolayer and TiAlN/TiAlSiN composite multilayer have been fabricated by magnetron sputtering method. It is found that the coating structure changes from columnar growth to nanocrystal growth by doping Si element. The TiAlN/TiAlSiN coating is composed by a coarse columnar TiAlN bottom layer and a fine nanocrystalline TiAlSiN top layer. Premature spalling problem (Lc2) is improved by forming the TiAlN/TiAlSiN multilayer structure. Titanium cutting experiment shows that the major wear mechanism of these coated tools is adhesive wear and chipping. The TiAlSiN coated tool has the longest cutting distance at various cutting speeds in these three kinds of coatings. This is because less built-up edge and chipping are generated at the cutting edge due to the dense nanocrystal structure, high hardness and good oxidation resistance of TiAlSiN coating. Therefore, the TiAlSiN coating with dense structure, high hardness and good oxidation resistance is recommended to use in high speed turning titanium. [ABSTRACT FROM AUTHOR]