The demand for high speed machining of Al-, Ti- and Ni- based alloys as well as the new MMC materials is ever growing. However, metallurgical reactions at the cutting interface lead to Built Up Edge (BUE) formation resulting in high cutting forces, high surface roughness and short tool lifetime. Novel TiAlCN/VCN coatings utilising nanoscale multilayer structure patented by Sheffield Hallam University [1], provide a solution to this problem.

Our research showed that during the growth of TiAlCN/VCN multilayer coating carbon dynamically segregates at the interfaces between the individual layers of the nanolaminated coating to form a lateral phase, which reduces their shear strength. This results in a dramatic change of the coating wear mechanism to a well-defined layer by layer wear on the nanometer scale, which turned out to be the key for prevention of thick built up layer formation when machining reactive Al- and Ti- based alloys [2].

TiAlCN/VCN nanoscale multilayer structured PVD coatings have been successfully produced by the combined High Power Impulse Magnetron Sputtering/ Unbalanced Magnetron Sputtering (HIPIMS/UBM) technique at SHU on various types of cutting tolls for machining of Al- and Ti- based alloys. The coatings were tested at the Fiat Research Centre and Airbus labs partnering in a multimillion European Project "ALTICUT" (download PDF).

In dry machining of Aerospace grade Al 7010-T 7651 alloy the coating showed factor of 4 longer tool life time as compared to state-of-the-art DLC coatings. In drilling of MMC materials at Airbus, TiAlCN/VCN coated drills produced 130 holes as compared to 2 holes produced with uncoated drills. Whereas in turning of Ti-alloys the TiAlCN/VCN coating produced 2-3 times more components, (orthopaedic implants) as compared to uncoated Cemented Carbide inserts.

[1]. P. Eh. Hovsepian, A. P. Ehiasarian, PVD Coated Substrate, GB0508485.0  filed 27 April 2005,  EP 1874981, 14.01.2009

[2]. Papken Eh. Hovsepian , Arutiun P. Ehiasarian , Anthony Deeming , Christian Schimpf . VMeCN Based Nanoscale Multilayer PVD Coatings Deposited by the Combined High Power Impulse Magnetron Sputtering/Unbalanced Magnetron Sputtering, (HIPIMS/UBM) Technology, Plasma Process. Polym. 2007, 4, S897-S901.