Graphite boats and trays are the standard carrier in sintering and heat treatment furnaces, but bare graphite reacts with the parts it carries. A plasma sprayed zirconia layer solves this: it is stable at high temperature and does not stick to the sintered product, so the boat can be used again and again.
In this video a six-axis robot holds the plasma gun and follows a programmed path across the boat. Robot motion gives a much more even coating thickness than manual spraying, which matters when a boat has deep pockets and complex walls.
Typical coating thickness is 0.05 to 0.3 mm. We also coat graphite crucibles, mandrels and fixtures with zirconia, alumina and yttria.
