High corrosion resistant ZrC films synthesized by ion-beamassisted deposition
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High corrosion resistant ZrC films synthesized by ion-beamassisted deposition Xiao-Ming He and Li Shu Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545
Hai-Bo Li and Duan Weng Department of Materials Science and Engineering, Tsinghua University, Beijing, 100084, People’s Republic of China (Received 13 February 1998; accepted 1 June 1998)
ZrC films with high hardness were deposited on A3 steel by ion-beam-assisted deposition and had a corrosion rate more than two orders less and a corrosion potential 0.19 V greater than those of the bare A3 steel. The corrosion current of ZrC films was 10 times less and the polarization resistance at least 7.82 times higher than those of both Teflon and ZrN films, respectively. The experimental results confirmed that ZrC films notably enhanced the corrosion resistance of steels. I. INTRODUCTION
The transition metal compound, zirconium carbide (ZrC), is of increasing interest for a number of applications that take advantage of its refractory properties, extremely high hardness, good metallic conductivity, and chemically stability.1–4 Recently, ZrC has been shown to improve the field emission stability and beam confinement while it was coated on the field emitter cathodes.1,2 Several deposition techniques, such as reactive magnetron sputtering,4 chemical vapor deposition,5 and vacuum plasma spray process,6 have been used to prepare ZrC films on high temperature (.380 ±C) substrates for electronic and mechanical investigations. However, the corrosion resistance of ZrC films prepared on low temperature substrates has rarely been investigated. High hardness ZrC with high corrosion resistance would be potentially used as a surface coating, especially for the surface modification of unclear materials. In this paper, the ZrC films synthesized by ion-beam-assisted deposition (IBAD) were demonstrated to have a remarkable enhancing behavior on corrosion resistance, as compared with the A3 steel as well as ZrN and Teflon coatings. To the best of our knowledge, the present work is the first report that ZrC films synthesized on steels by IBAD exhibit excellent corrosion resistance. II. EXPERIMENTAL
The commercial A3 steel in annealing condition was selected as the substrate. The composition of A3 steel is as follows: Element wt. %
C 0.18
Si 0.16
Mn 0.54
P S O Fe ,0.045 ,0.055 ,0.006 Balance
All steel samples of 12 3 12 3 2 mm3 in size were finely ground by silicon carbide papers, and then cleaned
ultrasonically in acetone, methanol, and de-ionized water, followed by air drying. ZrC films were prepared by using a multifunctional IBAD system with three Ar1 beam interactions, that is, two Ar1 beams to sputter a zirconium target and a graphite target separately to c-deposit the ZrC film while a third Ar1 beam was directed at the substrate to provide ion-assisted bombardment. In this unique processing, two sputtering Ar1 beam densities were adjusted to deposit the film with a desired ZryC atomi
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