Component in a combustion system, and process for preventing slag, ash, and char buildup

1. A process for preventing slag, ash, and char buildup on a surface, comprising:

disposing a composite on the surface;

replacing a component comprising the surface with a component consisting of the composite; or

a combination thereof;

wherein the composite comprises:

silicon carbide; and

a refractory metal silicide comprising a phase selected from Rm 5 Si 3 , Rm 5 Si 3 C, RmSi 2 , and a combination thereof;

wherein Rm is a refractory metal selected from molybdenum, tungsten, and a combination thereof; and

exposing the composite to slag, ash or char in a heated environment, wherein the slag, ash or char does not substantially wet the surface of the composite;

wherein disposing, replacing, or a combination thereof comprises welding the composite to a metal substrate, and further wherein the composite is in direct contact with the metal substrate.

2. The process of claim 1 , wherein disposing, replacing, or a combination thereof comprises welding, brazing, alloying, electric arc, electric spark, or a combination thereof.

3. The process of claim 1 , wherein the composite comprises a specific resistivity of about 0.000001 to about 0.5 ohm·cm.

4. The process of claim 1 , wherein the metal substrate defines the surface, a component in direct contact with the component comprising the surface, or a combination thereof.

5. The process of claim 1 , wherein a component comprises the surface, and wherein the component defines a gasifier, a gasification feed injector, an injector nozzle, a gasifier thermocouple, a gasifier thermocouple well, a gasifier thermocouple sheath, an injector barrel, an injector barrel cooling coil, a gasification feed injector shield, a gasifier lining, a gasification radiant syngas heat exchanger component, a gasification convective syngas heat exchanger component, a posimetric pump transition piece, a posimetric pump dry coal feed transition piece, a posimetric dry coal feed pump abutment, a posimetric pump dry coal feed rotor disk, a turbine bucket, a turbine blade, a turbine nozzle, a turbine rotor, a turbine disk, a turbine vane, a turbine stator, a turbine shroud, a turbine combustor, or a combination thereof.

6. A composite component for use in a combustion system, the composite comprising:

silicon carbide; and

a refractory metal silicide comprising a phase selected from Rm 5 Si 3 , Rm 5 Si 3 C, RmSi 2 , and a combination thereof;

wherein Rm is a refractory metal selected from molybdenum, tungsten, and a combination thereof and wherein the component comprises a metal substrate and the composite is welded to the metal substrate and is in direct contact therewith.

7. A composite component for use in a combustion system, the composite comprising:

about 50 to about 85 percent by volume silicon carbide;

about 4.9 to about 25 percent by volume of a phase of a refractory metal silicide selected from Rm 5 Si 3 , Rm 5 Si 3 C, and a combination thereof;

about 0.1 to about 20 percent by volume of a phase of a refractory metal silicide selected from RmSi 2 ; and

about 10 to about 45 percent by volume pores;

wherein percent by volume is based on a total volume of the composite;

wherein Rm is a refractory metal selected from molybdenum, tungsten, and a combination thereof;

wherein the composite comprises the molybdenum in an amount of about 45 to about 80 percent by weight and the tungsten in an amount of about 20 to about 55 percent by weight;

wherein the composite further comprises iron in an amount of about 0 to about 2 percent by weight; and wherein percent by weight is based on a total weight of molybdenum and tungsten;

and wherein the component comprises a metal substrate and the composite is welded to the metal substrate and is in direct contact therewith.

8. A process for preventing slag, ash, and char buildup on a surface in a combustion system, comprising:

disposing a composite on the surface;

replacing a component comprising the surface with a component consisting of the composite; or

a combination thereof;

wherein the composite comprises:

silicon carbide; and

a refractory metal silicide comprising a phase selected from Rm 5 Si 3 , Rm 5 Si 3 C, RmSi 2 , and a combination thereof;

wherein Rm is a refractory metal selected from molybdenum, tungsten, and a combination thereof

wherein disposing, replacing, or a combination thereof comprises welding the composite to a metal substrate, and further wherein the composite is in direct contact with the metal substrate.