Method for forming ceramic containing composite structure
A method for forming a ceramic containing composite structure is proposed comprising the steps of (a) feeding a ceramic component that sublimes and a metallic or semi-conductor material that does not sublime into a thermal spray apparatus, (b) spraying the ceramic component and the metallic or semi-conductor material onto a substrate, whereby the ceramic component and the metallic or semi-conductor material deposit on the surface of the substrate, and (c) keeping the metallic or semi-conductor material on the substrate surface plastic during spraying at least in the region where the metallic or semi-conductor material actually strikes the surface.
1. A method for forming a silicon carbide containing composite structure comprising the steps of (a) feeding an agglomerate having an average particle size of 50-100 μm comprising: (i) 30-97 weight percent of silicon carbide with an average particle size of about 20 μm or less (ii) 15 weight percent or less of a binder and (iii) the balance of the agglomerate being silicon with an average particle size of 25 μm or less into a thermal spray apparatus, (b) spraying the silicon carbide and silicon onto a substrate, whereby the silicon carbide and silicon deposit on the surface of the substrate, and (c) keeping the silicon on the substrate surface at a temperature which is at least 0.75 times the melting temperature in Kelvin of the silicon and at most 100 K above the melting temperature of the silicon during spraying at least in the region where the silicon carbide and silicon actually strikes the surface.
2. Method according to claim 1 wherein the spraying is conducted in a controlled atmosphere and/or low pressure between 0.0001 bar and 1 bar.
3. Method according to claim 2 wherein the controlled atmosphere comprises oxygen free environment and/or at least one inert gas.
4. Method according to claim 1 wherein the binder is selected from the group consisting of polyvinyl acetate, polyvinyl pyrrolidone, hydroxyethylcellulose, hydroxypropyl cellulose, hydroxypropyl methycellulose, polymethacrylate, methylcellulose, ethylcellulose, microcrystalline cellulose, gums, starches, sugars, waxes, and combinations of the foregoing.
5. Method according to claim 1 wherein the step of keeping the silicon at least 0.75 times the melting temperature in Kelvin of the silicon and at most 100 K above the melting temperature of the silicon comprises a controlled heating of the surface by means of a thermal spray beam generated by the thermal spray apparatus.
6. Method according to claim 1 wherein the step of keeping the silicon at least 0.75 times the melting temperature in Kelvin of the silicon and at most 100 K above the melting temperature of the silicon comprises transferring heat from an additional heat source to the substrate and/or the surface.
7. Method according to claim 1 wherein the thermal spray apparatus is plasma spray.
8. Method according to claim 1 wherein the thermal spray apparatus is an air plasma spray (APS), vacuum plasma spray (VPS), low pressure plasma spray (LPPS), radio frequency plasma, plasma transfer arc, microwave, high velocity oxy-fuel (HVOF), high velocity air fuel (HVAF), high velocity liquid fuel (HVLF), combustion, induction and laser.
9. Method according to claim 1 wherein the silicon carbide containing composite structure comprises ceramic or graphite fibers, filaments, matte, or whiskers and/or the ceramic containing composite structure comprises pores, solid lubricant particles, or tribological enhancing additives.
10. Method according to claim 1 wherein the silicon carbide containing composite structure formed on the substrate is a coating.
11. Method according to claim 1 wherein the silicon carbide containing composite structure is a free-standing structure.
12. Method according to claim 1 wherein the temperature is at least 0.8 times the melting temperature in Kelvin.
13. Method according to claim 1 wherein the temperature is at most 50 K above the melting temperature.