INTERFACIAL REACTIONS OF TANTALUM THIN LAYER ON HIGH STEEL SUBSTRATE

Yazid Hadjar ,  Rachid Halimi 

Université de Constantine, Laboratoire des Couches Minces et Interfaces, Route de Ain El-Bey, Constantine 25000, Algeria

Abstract

Interfacial reactions between a tantalum thin layer (4 µm thickness) and a high steel substrate (containing 1% of carbon) on vacuum annealing from 600 to 1100C were investigated by X- ray diffraction (XRD), secondary ion mass spectroscopy (SIMS), Auger electron spectroscopy (AES) and scanning electron microscopy (SEM). The product phases identified by X-ray diffraction are Ta2C and TaC in a temperature range 800-900C. At T≥ 900C no more unreacted tantalum is detected and the stable phase TaC grows at the expense of the binary carbide Ta2C. SIMS and AES analyses show that the adapted thermal annealing allows the diffusion of the carbon atoms from high steel substrate towards the thin layer of tantalum, and causes thereafter the transformation of this last into tantalum carbide. It is found, that the interfacial reaction of coating with steel substrate start at 600C, and the formed carbides grow from steel substrate to the free surface of coatings. Observation of surface and cross section morphology by SEM shows a good adhesion of formed coating layer. Finally, we discuss the mechanisms that may account for the considerable performance of these coatings.

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Presentation: poster at E-MRS Fall Meeting 2005, Symposium F, by Yazid Hadjar
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-05-03 15:37
Revised:   2009-06-07 00:44
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