Siliciumnitrid-Kompositpulver fuer thermische Beschichtungstechnologien und Verfahren zu ihrer Herstellung

A modified silicon nitride composite powder, for thermal coating technology, consists of silicon nitride particles in an oxynitride or silicon binder matrix, the matrix making up 10-40 (20-35) vol.% of the total powder volume and the powder particle size (d50) being up to 100 (20-63 or 20-45) mu m. The binder matrix forms a liquid phase under the thermal coating conditions. Also claimed are (i) a process for producing the composite powder with an oxynitride or silicon binder matrix by (a) homogenising and granulating a mixture containing silicon nitride and/or silicon and one or more oxides or a mixture containing silicon and optionally silicon nitride; (b) subjecting the granules to one or more heat treatments in a nitrogen-containing atmosphere at 0.5-100 bar; and then (c) grinding; and (ii) a process for producing the composite powder with a silicon binder matrix by (a) homogenising and granulating a silicon-containing mixture; and (b) spraying the granules at above the melting temp erature of silicon into a liquid. USE - For thermal spray coating of heavy duty components such as chemical equipment with silicon nitride layers. ADVANTAGE - The powder allows production of homogeneous silicon nitride coatings by conventional coating techniques such as plasma spraying (including the APS, CAPS and VPS (LPPS) variants), flame spraying (including the HVOF variant) and laser coating.