WC based cermet coatings have been considered as alternative replacements to the more
traditional hard chrome plating for improved surface properties of aircraft landing gear.
While these coatings are used in engineering applications requiring superior hardness and
improved wear resistance, little is known about the corrosion resistance.
In this study, three WC based composite coatings were deposited onto ferritic stainless steel
substrates using high velocity oxy fuel (HVOF) technology. Salt spray testing and
potentiodynamic scanning studies in a saline environment were conducted on the coatings.
Characterisation of the coating structure, composition and morphology, was carried out,
prior to and after corrosion testing, using optical microscopy, scanning electron microscopy
and EDX elemental analysis.
The results showed that poor corrosion performance was exhibited by all three coatings.
This was attributed to the high levels of porosity and the presence of micro-cracks within the
coatings, resulting in attack of the substrate directly by the saline environment and possible
galvanic coupling effects between the substrate and the coating. Dissolution and / or erosion
of specific phases within the coating, resulting in the formation of micro-channels and
increased number / size of voids may have accelerated corrosion of the system.
Nascimento, M. P., Souza, R.C., Miguel, I.M, Pigatin, W. L. and Voorwald, H. J. , 2001,
“Effects of Tungsten Carbide Thermal Spray Coating by HP/HVOF and Hard Chromium
Electroplating on AISI 4340 High Strength Steel”, Surface and Coatings Technology,
Vol. 138, pp. 113-124.
Natishan, P. M., Lawrence, S. H., Foster, R. L. and Sartwell, B. D., 2002, “Atmospheric
Corrosion Study of Electrodeposited Hard Chromium and High-Velocity Oxygen-Fuel
Thermal Spray Coatings”, Corrosion, Vol. 58, Ed. 2, pp. 119-123.
Perry, J. M., Neville A. and Hodgkiess, T., 2002, “A Comparison of the Corrosion
Behaviour of WC-Co-Cr and WC-Co HVOF Thermally Sprayed Coatings by In Situ
Atomic Force Microscopy (AFM)”, Journal of Thermal Spray Technology, Vol. 11, Ed.
4, pp. 536-541.
Godoy, C., Lima, M. M., Castro, M. M. R. and Avelar–Batista, J. C., 2004, “Structural
Changes in High Velocity Oxy – Fuel Thermally Sprayed WC-Co Coatings for Improved Corrosion Resistance”, Surface and Coatings Technology, Vol. 188-189, pp. 1-6.
Aw, P.K., Tan, A. L. K., Tan, T. P. and Qiu, J., 2008, “Corrosion Resistance of Tungsten
Carbide Based Cermet Coatings Deposited by the High Velocity Oxy Fuel Spray
Process”, Thin Solid Films, Vol. 516, pp. 5710-5715
Espallargas, N., Berget, J., Guilemany J. M., Benedetti, A. V. and Suegama, P. H., 2008,
“Cr3 C2–NiCr and WC–Ni Thermal Spray Coatings as Alternatives to Hard Chromium for Erosion–Corrosion Resistance”, Surface & Coatings Technology, Vol. 202, pp. 1405–1417.
Liu, Z., Cabrero, J., Niang, S. and Al-Taha, Z. Y, 2007, “Improving Corrosion and Wear
Performance of HVOF-Sprayed Inconel 625 and WC-Inconel 625 Coatings by High
Power Diode Laser Treatments”, Surface & Coatings Technology, Vol. 201, pp. 7149–
Zhang, S. H., Yoon, J. H., Li, M. X., Cho, T. Y., Joo, Y. K. and Cho, J.Y., 2010,
“Influence of CO2 Laser Heat Treatment on Surface Properties, Electrochemical and Tribological Performance of HVOF Sprayed WC–24%Cr3C2–6%Ni Coating”, Materials Chemistry and Physics, Vol. 119, pp. 458–464.
Cho, J. E., Hwang, S. Y. and Kim, K.Y., 2006, “Corrosion Behaviour of Thermal
Sprayed WC Cermet Coatings Having Various Metallic Binders in Strong Acidic
Environments, Surface and Coatings Technology, Vol. 200, pp. 2653-2662.
Koon, A. P., Hee, T. B., Taylor, M. , Western M. and Yip, J., 1999, Hard Chrome
Replacements by HVOF Sprayed Coatings, SIMTech Technical Report (Pt/99/002/ST),
Surface Technology Group, Process Technology Division.
Stokes, J., 2008, The Theory and Application of the HVOF Thermal Spray Process,
Dublin City University, ISBN 1-87232-753-2, ISSN 1649-8232 <
Warsono, R., 2004, Development of HVOF Sprayed Tungsten Carbide Nickel Coatings
Deposited on Stainless Steel Substrates for Corrosion Protection in the Aerospace
Environment, Internal Report, RMIT University, Melbourne.