AVS 52nd International Symposium
    Advanced Surface Engineering Monday Sessions
       Session SE-MoM

Invited Paper SE-MoM9
Established Protective Cutting Tool Coatings for Difficult Machining Operations

Monday, October 31, 2005, 11:00 am, Room 201

Session: Nanocomposites and Coatings with Enhanced Thermal Stability
Presenter: K. Bobzin, RWTH Aachen University, Germany
Authors: K. Bobzin, RWTH Aachen University, Germany
M. Maes, RWTH Aachen University, Germany
C. Pinero, RWTH Aachen University, Germany
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This paper presents a review of the most important thin coatings developed for the protection of cutting tools. Special attention was given to the development of promising coatings for difficult machining operations. Because of the increasing of the complexity in the aircraft and nuclear industry and the elevated operating temperatures, super alloys were developed from simple nickel-chromium matrix to multi-element, multi-phase systems. These new nickel-based super alloys are specially favored for their exceptional thermal resistance and ability to retain mechanical properties at elevated temperatures. However, they are classified as difficult-to-machine materials due to their high shear strength, work hardening tendency, highly abrasive carbide particles in the microstructures, strong tendency to weld and form built-up edges. Also, their tendency to maintain a high strength at the elevated temperatures generated during machining because of their low thermal conductivity constitutes an important challenge. Nowadays, TiAlN is well known because of its excellent overall performance in cutting operations. Also crystalline Al@sub 2@O@sub 3@ shows a high potential for the protection of cutting tools due to its very good chemical and thermal properties. However an adequate coating system for machining super alloys was not found yet. In order to obtain the appropriated properties combination in a single coating system, different TiAlN + @gamma@-Al@sub 2@O@sub 3@ coating system combinations were deposited on cemented carbide cutting inserts and characterized by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). Surface energy of the coated samples was measured. Tribological and chemical properties were analyzed at room and high temperatures.