TITLE:
Corrosion Behaviour of Modified HVOF Sprayed WC Based Cermet Coatings on Stainless Steel
AUTHORS:
L.P. Ward, B. Hinton, D. Gerrard, K. Short
KEYWORDS:
HVOF, WC, Structure, Characterisation, Salt Spray Testing, Potentiodynamic Scanning
JOURNAL NAME:
Journal of Minerals and Materials Characterization and Engineering,
Vol.10 No.11,
September
12,
2011
ABSTRACT: 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.