Layer that provides the coating's main function, such as wear, insulation, abradability or corrosion resistance, applied over a bond coat. Examples include zirconia over MCrAlY in thermal barriers and alumina-titania or chrome oxide over nickel-aluminum on wear parts. Top coat thickness, porosity and microstructure are usually the most tightly specified properties on the drawing.
Top coat has to be 0.012 to 0.016 after grind, so shoot it to 0.020 and leave stock.
Also heard as
- topcoat
- functional coat
- ceramic top
Related terms
Bond coat
The first layer sprayed on a substrate to help the following coat stick and sometimes protect the metal.
YSZ
Yttria-stabilized zirconia: the standard ceramic for thermal barrier top coats.
Thermal barrier coating
A ceramic coating system that insulates hot-section metal parts from combustion gas temperatures.
Grind stock
Extra coating thickness sprayed beyond the final size so it can be ground or machined to finish.