Community Research and Development Information Service - CORDIS

DEVELOPMENT OF CORROSION RESISTANT COATINGS BY HIGH VELOCITY OXY-FUEL (HVOF) SPRAYING

The main objective of the project has been to establish high velocity oxy-fuel (HVOF) spraying as a new technology for corrosion resistant coatings. State-of-the-art HVOF spraying systems (Diamond Jet and JP5000, representing two of the most widely used commercial systems throughout Europe) have been employed. A range of experimental and commercially available spray powder compositions have been investigated, including the nickel based alloys Hastelloy C276 and Alloy 59, duplex stainless steel S32750, the cobalt based alloy Ultimet (UNS R31233) and the iron based alloy AE7228. The HVOF sprayed coatings have been deposited on carbon steel discs. The corrosion resistance of the coated samples has been determined electrochemically, primarily by potentiostatic polarisation measurements in 6% ferric chloride solution (ASTM G48) and substitute seawater (ASTM D1141), respectively.

The main results can be summarized as follows:

- Best practice information on the application of HVOF coatings by Diamond Jet hybrid and JP5000 systems has been developed both with respect to corrosion resistance and cost.
- Models have been developed for the JP5000 and Diamond Jet DJ2700 (propylene fuel) systems to predict improved spraying parameters.
- A significant improvement in the corrosion resistance of HVOF sprayed coatings has been achieved by optimisation of powder and spraying parameters.
- Specifically, Hastelloy C276 coatings sprayed on the DJ2600 (hydrogen fuel) system exhibit improved corrosion resistance. By narrowing the powder size distribution, similar corrosion properties can be obtained on the JP5000 system. However, the corrosion resistance of 0.3 mm thick HVOF coatings is generally inferior to the thicker weld overlay equivalents used as reference materials.
- A corrosion test cell and procedure has been developed for studying the corrosion behaviour of thermally sprayed coatings, allowing a large number of coated samples to be electrochemically characterised in an efficient way.

The improved spraying procedures developed in this project can now be applied by SMEs to produce coatings with improved corrosion resistance and at a reduced cost. The models developed for the JP5000 and Diamond Jet DJ2700 (propylene fuel) can be used to predict improved spraying parameters for materials not used in this project. In particular, the models have been applied to cermet coatings.

Reported by

SINTEF
Richard Birkelandsv 3A
7465 Trondheim
Norway
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