Characterisation of CVD Niobium Carbide Coatings on Hard Carbide Substrate
Abstract
Hard coatings are often used for mechanical properties such as wear and friction resistance. The corrosion behaviour may also be an important criterion for industrial applications of these coatings. In this paper, the protective behaviour of niobium carbide coatings onto hard carbide substrate was investigated in 3% NaCl and 1M H2SO4 solutions. The corrosion behaviour of the carbide coatings depends not only on the intrinsic electrochemical properties of the coatings, but depends also by the surface defects such as roughness, deposited droplets during CVD process and mainly by pinholes, cracks and scratches. The experiments conducted to obtain thin layer of carbide through the vapour chemical deposition method have followed an original path to obtain NbC directly in the working room thus avoiding the import of these hazardous substances.
Characterisation of coating deposed by CVD method was done using scanning electron microscope (SEM), X-ray diffractometer (XRD) and Knoop hardness. Scanning Electron Microscope was used to investigate the coating morphology and interface structure. X-ray mapping were also performed to characterise the elements in a semi-quantitative analysis. Dron X-ray diffractometer with Mo Kα radiation operating was used for phase(s) identification. Microhardness value (Knoop hardness) measured in the coating layer was 30.000 MPa.
Downloads
References
[2]. M. D. Gavril (Donose), C. Gheorghies, A. M. Cantaragiu, D. C. Vladu (Radu), S. Donose - Effect of acidic environment on Cu-Al2O3 codeposition, The Annals of” Dunarea de jos “University of Galati, Fascicle IX. Metallurgy and Materials Science, No.4, (2011), ISSN 1453 – 083X, p.16.
[3]. P. Hagioglu, C. Gheorghies, A. M. Cantaragiu, Boiciuc, N. Tigau - Corrosion behaviour of Tombac used in cult objects manufacturing, The Annals of” Dunarea de jos “University of Galati, Fascicle IX. Metallurgy and Materials Science, No.2, (2009), ISSN 1453-083X, p.1159.
[4]. S. Constantinescu, T. Radu - Advanced methods of obtaining thin coats, Ed.Ştiinţifică F.M.R. ISBN 973-8151-25-2 Bucureşti, (2003).
[5]. S. Constantinescu - Studies on Thin Carbide and Nitride Layers Deposition on Metal Basis, Based on Chemical Reaction at High Temperatures, Academic Thesis, Galati, (1998).
[6]. S. Constantinescu, T. Radu, M. Vlad, L. Orac - Wearresistence of the WC-Co alloys used for short chip materials cutting, Proceedings GEOENV 2008, Geoenvironment and Geotechnics, Publisher by Heliotopus Conferences, ISBN 978-960-6746-01-7, Millos, Greece, (2008).
[7]. S.E. Rodil, J.J. Olaya, S. Muhl, B. Bhushan, G. Wei - Surf. Coat. Technol. 201 (2007) 6117.
[8]. S. Constantinescu - Nitride coatings on widia substrate for mechanical applications, Journal Surface Engineering vol., p. 77-81, (2009), ISSN 0267-0844, www.ingentaconnect.com.
[9]. M Tawfik., A. A. Alfantazi, E. Asselin - Corrosion of niobium in sulphuric and hydrochloric acid solutions at 75 and 95 °C, Corrosion Science, 49 (2007) 694-710.
[10]. A. Robin- Comparative study of Nb, Nb–10W, and Nb–16Ta–12W corrosion behavior in sodium hydroxide solutions, Electrochimica Acta, 49 (2004) 1915-1923.
[11]. A. Robin - Corrosion behaviour of niobium in sodium hydroxide solutions, Journal of Applied, Electrochemistry 34 (2004) 623-629.
[12]. L. Orac, V. Grechanyuc - Corrosion resistance of the composites Cu-Mo obtained by PVD method, METAL 2010, Ostrava, Czech Republic, p. 932-937.