The excellent wear resistant properties of high velocity oxyfuel (HVOF) carbide coatings are well established. Good corrosion resistance can also be achieved with these coatings when optimum coating and substrate combinations are selected. Over the past decade, HVOF has been increasingly considered as an alternative to hard chrome plating for several applications, in particular those experiencing severe combined wear and corrosion [8] . Some of the advantages of HVOF coatings over hard chrome plating include:
- less environmental impact with no major ecological and health & safety concerns [4]
- WC/Cr/Co coating has abrasion wear resistance 4 to 5 times higher than hard chrome [5,6]
- coatings have negligible impact on substrate fatigue performance, whilst hard chrome plating reduces substrate fatigue performance by 30-50% [1]
- extended seal life on hydraulic components [3]
- requires less masking than hard chrome plating and offers improved deposition quality adjacent to holes and keyways [7]
- hard chrome plated high strength steels require heat treatment to prevent hydrogen embrittlement; this is not required with HVOF coatings [4]
- coating of a wide range of materials with coating material tailored to the application, e.g. WC/Co/Cr, WC/Co, Cr3C2/NiCr, WC/Ni coatings, and nickel-based corrosion resistant alloys
- whole-life cycle costs of carbide coatings estimated to be 50% of hard chrome plating [7]
HVOF coatings are already being considered for specific components including aircraft landing gear, propeller hubs and gas turbine journals. [1-3] The use of wear and corrosion resistant HVOF coatings is also proposed for hydraulic rams on heavy construction machinery such as earth moving equipment, for underwater marine hydraulic rams and for offshore applications such as valves and pumps. [4]
References
- B D Sartwell, P. M. Natishan, I.L Singer, K Legg, J. D Schell, J. P Sauer: Replacement of chromium plating using HVOF thermal spray coatings.
- J D Schell, M Rechtsteiner: Replacement of chromium plating using advanced material technologies on gas turbine components.
- K Legg, B Sartwell: Hard Chromium Alternative Team update - Improving performance while reducing cost.
- T Lester: Replacing hard chromium by thermally sprayed coatings, Welding & Metal Fabrication, August 1999.
- UKHealth & Safety Executive
- C Reignier, A Sturgeon, D Lee, D. De Wet: HVOF sprayed WC-Co-Cr as a generic coating type for replacement of hard chrome plating, to be published in the ITSC 2002 proceedings.
- M E Graham, K O Legg, T Bernecki: HVOF as a repair technology replacement for hard chrome, Proceeding of the 4th Thermal Spray Coatings organised by Gorham Advanced Materials Inc, 1997.
- B D Sartwell, K Legg, P E Bretz: status of HCAT/JG-PP program on replacement of hard chrome plating with HVOF thermal spray coatings on landing gear.
Further information
FAQ: What is hard chrome plating?
See further information about Materials & Corrosion Management.