Study of diamond adhesion behavior on chromium and titanium for obtaining adherent diamond coatings on steel
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J. Gra´cio Department of Mechanical Engineering, University of Aveiro, 3810 Aveiro, Portugal
E. Pereira Department of Physics, University of Aveiro, 3810 Aveiro, Portugal
N. Alia) and W. Ahmed Department of Chemistry and Materials, Manchester Metropolitan University, John Dalton Building, Chester Street, Manchester M1 5GD, United Kingdom (Received 29 March 2000; accepted 24 July 2000)
It is known that diamond films display poor adhesion on metals such as copper and steel. One solution to overcome the poor adhesion is to use interlayer materials. In this study we report results of an investigation of the adhesion behavior of diamond on pure chromium (Cr) and titanium (Ti) substrates. Cr and Ti are promising interlayer materials for adhering diamond to stainless steel. The coating adhesion was studied using indentation tests combined with acoustic emission signals during loading. It was found that a 105-N load indentation caused the film to delaminate from the Cr substrate, while the diamond film remained attached to the titanium even after the indentation at 180 N. Micro-Raman spectroscopy was used to monitor the film stress. The diamond films grown on Ti substrates were found to be less stressed than the films grown on Cr substrates. Therefore, Ti was used in thin-film form to obtain adherent diamond coatings on steel.
I. INTRODUCTION
Diamond displays an excellent combination of properties that make it suitable for a range of industrial applications.1–4 As a result, researchers have endeavored to fabricate diamond using a number of deposition methods. Diamond deposition using chemical vapor deposition (CVD) has been widely reported. However, low diamond nucleation densities and poor diamond adhesion on metals such as steel and copper have been an ongoing concern for diamond researchers at large. As the majority of the applications of diamond demands sufficiently dense and adherent coatings, it becomes important to optimize both diamond nucleation density and coating adhesion. Diamond deposition on strong carbide-forming materials (e.g., silicon) usually produces adherent coatings. In contrast, diamond deposited directly on strong carbondissolving materials, such as steel, or on noncarbon affinity materials, like copper, displays poor adhe-
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J. Mater. Res., Vol. 15, No. 11, Nov 2000 Downloaded: 16 Mar 2015
sion.5–10 A number of researchers have attempted to improve the adhesion of diamond coatings on such metals.11,12 The ductile nature of Ti and Cr, together with the fact that both materials are carbide forming, makes them promising candidates for use as interlayer materials. Metallic intermediate layers, including Cr and Ti, have been used by some workers to enhance diamond adhesion on copper and steel substrates.13,14 However, there have been no reports of comparative study on the adhesion of diamond films grown directly on pure bulk Cr and Ti substrates. Diamond coating adhesion can be assessed usin
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