Patent ID: 6468648
Filing Date: 2002-10-22
Classification: C04B,C23C,F01D,F05D,Y10T

Abstract:
A product formed by the process of plasma spraying a mullite coating onto a surface of a ceramic substrate, said process comprising the steps of:providing a ceramic substrate having a surface to be sprayed; maintaining a plasma spray gun nozzle outlet within a predetermined distance from said surface to be sprayed, wherein a flame exits from said outlet and at least temporarily resides against said surface to be sprayed; moving said surface to be sprayed and said outlet relative to one another to limit the residence time of the flame against said surface; introducing a fused and crushed mullite powder of a predetermined particle size into the flame at a predetermined powder feed rate wherein said mullite powder has a crystallization temperature; maintaining the substrate at a temperature below the mullite powder crystallization temperature; selecting said particle size, said powder feed rate, said predetermined nozzle outlet distance and the speed at which said nozzle outlet and said surface move relative to one another, such that the mullite powder particles are not heated to such a high temperature as to cause excessive dissociation of the mullite within the flame but sufficiently high to melt said surfaces of said particles; and whereby the applied coating is at least 85% by volume crystalline mullite and about 0.5% to about 15% by volume amorphous material and dissociated phases of mullite.