The machining of difficult-to-cut materials such as nickel-based alloys and austenitic steels are focus in a lot of investigations for a long time. When machining these materials, different effects are overlapping. Approaches to overcome the several problems when machining these materials can be an appropriate coating system for the cutting tool as well as innovative lubricants. Coatings are one of the most common possibilities to improve the cutting performance of tools, notably the tool life as well as the material removal rate. Aluminium oxide coatings made by Physical Vapour Deposition (PVD) technology is a promising coating material for cutting operations. Due to its outstanding characteristics, such as high hardness, high thermal stability and low tendency to adhesion aluminium oxide is a predestined material for the machining of difficult-to-cut materials. In combination with innovative environmental friendly lubricants, the performance of cutting tools is increasing significantly. The objective of this work is to study the wear mechanisms and the cutting performance of aluminium oxide based coated tools in turning, drilling and milling operations.