TWI Industrial Member Report Summary 539/1996
M D F Harvey
High velocity oxyfuel (HVOF) spraying provides an exciting new opportunity for producing high quality ceramic coatings. A method is described for the deposition of functionally graded metal- ceramic coatings, which are designed to improve ceramic coating stability on metal substrates.
Oxide ceramics have a wide range of properties, eg wear resistance, chemical inertness and resistance to electrical conduction and thermal heat transfer, which makes them attractive as coatings. Thermal spraying, and in particular plasma spraying, is well established as a process for depositing ceramic coatings, but the HVOF process provides a new route for depositing ceramic coatings with potentially superior properties.
It is standard practice to improve ceramic coating adhesion and resistance to thermally-induced stresses by applying a bondcoat. Occasionally, an additional metal-ceramic interlayer may be used. This study establishes the feasibility of depositing multilayer metal-ceramic coatings by the TOPGUN HVOF system. Two coatings were selected to offer wear and corrosion resistance in low temperature (<300 degrees C) aqueous and high temperature (up to 800 degrees C) gaseous environments, i.e. Al-Al2O3 and NiAl-Al2O3.
- To demonstrate the feasibility of co- spraying a metal and ceramic powder simultaneously, by HVOF spraying, and to deposit metal-ceramic layers of controlled composition.
- To demonstrate the feasibility of depositing a graded Al-Al2O3 coating.