Composite intermediate layer for CVD diamond film on steel substrate
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Composite intermediate layer for CVD diamond film on steel substrate Andre Contin1, Getúlio de Vasconcelos2, Djoille D. Damm1, Vladimir J. Trava-Airoldi1, Raonei A. Campos3, Evaldo J. Corat1 1
National Institute for Space Research, São José dos Campos, SP, 12227-010, Brazil. Institute for Advanced Studies, São José dos Campos, SP, 122288-001, Brazil. 3 Federal University of South and Southeast of Pará, PA, 68507-590, Brazil. 2
ABSTRACT The union of the unique diamond properties with steel (most common substrate material) provides a new solution for machine parts under critical mechanical conditions and severe environmental. However, CVD diamond coating directly on steel comes with several issues. The fundamental reasons for the lack of adhesion are an iron catalytic effect, the high carbon solubility in iron and high mismatch in thermal expansion coefficient of diamond and steel. The use of interlayer may solve these issues acting as a diffusion barrier, for both iron and carbon, and match thermal expansion coefficients. Several articles describe the PVD deposition or electroplated interlayer. In the present study, the diamond film coated steel with an intermediate barrier deposited by laser cladding process. In this novel technique, laser irradiation melts the powder (preplaced) and the substrate surface to create the coating on a steel substrate. We used the SiC/Ti and SiC/Cu powder mixtures to create the intermediate barrier. Diamond film deposition was carried out in an HFCVD reactor (Hot Filament Chemical Vapor Deposition). The samples characterization included X-ray Diffraction (XRD); Field Emission Gun - Scanning Electron Microscopy (FEG-SEM) and Raman Scattering Spectroscopy (RSS). Results showed that laser incidence dissociated partially the SiC powder, forming FeSi, Cu3Si phases. Further, the composite layer assisted the high thermal stress relief in steel/diamond interface. INTRODUCTION Diamond physical properties present niche industrial applications. Diamond is the hardest known natural material, its most attractive physical property. In addition, it withstands aggressive environment and shows the low coefficient of friction. At tools, the single crystal diamond tool would be the most wear resistance one, on the other hand, the diamond tool would not show fracture toughness, leading to disastrous failure under extreme working conditions [1]. Steel is the most widely used metal material in the industrial applications and presents high fracture toughness. Thus, by depositing CVD diamond film on steel substrates, the high steel toughness combined with high diamond hardness may result in excellent wear resistance, making it ideal for various applications. However, there is a lack of adhesion between diamond film grown directly on steel, because of three main problems. First, the iron catalytic effect at CVD temperatures leads to graphitic soot creation at substrate surface. Second, the high carbon solubility in iron results in a prolonged time for diamond nucleation. Third, there is a large mismatch in th
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