Effect of chromium content on microstructure and corrosion behavior of W--Cr--C coatings prepared on tungsten substrate

Abstract

W--Cr--C coatings with different chromium contents (0--3 wt.%) were fabricated on the tungsten substrates by spark plasma sintering (SPS) method from the graphite and chromium mixed powders. SEM and XRD were exploited to analyze the effect of Cr contents on the microstructure of coatings. It was found that the abnormal hollow WC grains disappeared with addition of Cr less than 2%, and the microstructures were largely refined and densified. With further increase of Cr addition, the grains changed slightly but the densification was reduced. The most dense coating was achieved at 1 wt.% Cr. Corrosion behavior of the W--Cr--C coatings were investigated by impedance spectrum and potentiodynamic polarization tests. Results suggested that the W--1Cr--C coated W sample exhibited the lowest corrosion current density and highest corrosion potential due to the most densified microstructure, indicating that the addition of Cr at 1 wt.% was optimal for WC coating against corrosion.

Keywords

W--Cr--C coating / spark plasma sintering (SPS) / corrosion resistance / electrochemical measurement

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Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (Grant Nos. 11075177 and 51101152) and the Tribology Science Fund of State Key Laboratory of Tribology (Grant No. SKLTKF12B13).

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2014 Higher Education Press and Springer-Verlag Berlin Heidelberg