AVS 58th Annual International Symposium and Exhibition
    Advanced Surface Engineering Division Thursday Sessions
       Session SE+PS-ThA

Paper SE+PS-ThA6
Structure Evolution and Wear Mechanism in TiAlCN/VCN Nanoscale Multilayer Coatings Deposited by Reactive High Power Impulse Magnetron Sputtering Technology

Thursday, November 3, 2011, 3:40 pm, Room 104

Session: Pulsed Plasmas in Surface Engineering
Presenter: Papken Hovsepian, Sheffield Hallam University, UK
Authors: P. Hovsepian, Sheffield Hallam University, UK
A.P. Ehiasarian, Sheffield Hallam University, UK
G.K. Kamath, Sheffield Hallam University, UK
R. Haasch, University of Illinois at Urbana Champaign
I. Petrov, University of Illinois at Urbana Champaign
Correspondent: Click to Email
2.5 µm thick TiAlCN/VCN coatings were deposited by reactive HIPIMS process. XTEM showed gradual evolution of the structure of the coating with thickness. The initial structure is nanoscale multilayer with sharp interlayer interfaces. This transforms to nanocomposite of TiAlCN and VCN nanocrystalline grains surrounded by C-rich tissue phase and finally changes to an amorphous carbon rich Me-C phase. In contrast deposition in similar conditions using standard magnetron sputtering produces a well defined nanoscale multilayer structure. Depth profiling by AES showed that the carbon content in the HIPIMS coating gradually increased from 25% at the coating substrate interface to 70% at the top thus supporting the TEM observations.

Energy-resolved mass spectrometry revealed that HIPIMS plasma is a factor of 10 richer in C1+ ions, and therefore more reactive, as compared to the plasma generated by standard magnetron discharge at the same conditions. The peculiar structure evolution in HIPIMS is discussed in relation to target poisoning effect and carbon outward diffusion during coating growth.

Highly abrasive AlSi9Cu1 alloy was dry machined using TiAlCN/VCN coated 25 mm diameter end mills to investigate the coating-work piece material interaction. Green (532 nm excitation) and UV (325 nm excitation) Raman spectroscopy was employed to identify the phase composition of the built up material on the cutting edge and swarf surfaces produced during machining. These analyses revealed formation of lubricious Magnèli phases namely V2O5 and graphitic carbon as well as highly abrasive SiO2 and Al2O3 thus shedding light on the wear processes and coating tribological behaviour during machining.