AVS 46th International Symposium
    Thin Films Division Thursday Sessions
       Session TF-ThA

Paper TF-ThA5
Structural Determination of Wear Debris Generated from Sliding Wear Tests on Ceramic Coatings Using Raman Microscopy

Thursday, October 28, 1999, 3:20 pm, Room 615

Session: Ex-situ Characterization
Presenter: C.P. Constable, Sheffield Hallam University, UK
Authors: C.P. Constable, Sheffield Hallam University, UK
J. Yarwood, Sheffield Hallam University, UK
P. Hovsepian, Sheffield Hallam University, UK
L.A. Donohue, Sheffield Hallam University, UK
W.-D. Münz, Sheffield Hallam University, UK
Correspondent: Click to Email
During sliding, the high pressure at the point of contact can contribute to high flash temperatures, which are not accurately measurable. The magnitude of these flash temperatures has been quoted as being up to several hundred degrees Celsius for some systems but remains a topic for debate. Tribologists interested in ceramic coatings are realising that the wear debris can bear the signature of the wear process and the composition of the debris can enable an estimate of these contact temperatures. Raman microscopy is utilised here for the identification of compounds, especially oxides, generated during the wear process to endeavour to gain a better understanding of tribochemical reactions. A series of PVD ceramic hard coatings; CrN/NbN, CrN, NbN, TiAlN/VN, TiAlCrYN and TiCN have been deposited on steel substrates using the cathodic arc/unbalanced magnetron deposition technique. Ball-on-Disk sliding wear tests against corundum were performed for all the above coatings. The debris generated were characterised using vibrational spectroscopy; namely Raman microscopy. The high spatial resolution (2µm), in-situ capability, sensitivity to structural changes and non-destructive nature make this technique ideal for the study of such small amounts of wear debris. Previous work has centred on TiN coatings. This paper attempts to broaden the discussion to include other more complex monolithic and multilayered superlattice coatings. Under dry sliding conditions of 5N normal load, 10cms@sup -1@ in ambient air (humidity ~33%) titanium based alloy coatings were found to provide TiO@sub 2@ (rutile) debris. However the addition of fine layers of VN to the TiAlN system provided lower friction coefficient, wear rate and less debris through the possible formation of a lubricious surface oxide. CrN and NbN based coatings were also found to produce debris with Raman bands corresponding to various oxides.