Description
The machining of difficult-to-cut materials such as titanium plays a key role in several industries such as aerospace or medical. Approaches to overcome many difficulties when machining these materials, such as the long-chipping behaviour and tool wear due to the work hardening of titanium, can be an appropriate coating system for cemented carbide cutting tools. However, the atmosphere under which machining takes place, influencing the chemical tool wear, has not been taken into consideration. This work examines the tribochemical wear resistance of TiN, TiAlN and CrAlN coated carbide tools under different atmospheric conditions when cutting Ti6Al-4V. Air, technically pure argon and silane-doped argon is used to determine the influence of different oxygen levels on the wear behaviour of the tools. It has been found that oxidation of tools and tool coatings plays a significant role in tool wear when dry cutting titanium. Best results were generated using CrAlN and uncoated inserts where an increase in tool life up 60 % can be achieved when cutting in oxygen levels corresponding to extreme high vacuum (XHV) adequate atmospheres by using silane-doped argon. The benefits of XHV adequate atmospheres also have an effect on TiAlN- and TiN based coatings, but the chemical interaction of Ti element in the coating with the workpiece material, which presumably reduces wear resistance of cutting tools, cannot be outweighted or equalised by applying oxygen free atmospheres.
