Oxidation resistant, high temperature thermal cycling resistant coating on silicon-based substrates and process for the production thereof

Claim 2

A coated article comprising: a fully dense shaped substrate body of a silicon nitride- or silicon carbide-based monolithic or composite material; an adherent, continuous, fully dense intermediate layer about 0.5-20 microns thick of an aluminum nitride or aluminum oxynitride material over and chemically bonded to the substrate body; and an adherent, continuous, fully dense first outer layer about 0.5-900 microns thick comprising an oxide of aluminum or zirconium over and chemically bonded to the intermediate layer; wherein each layer is a graded layer changing in composition from the material over which it is deposited to the material of the layer and further to the material, if any, deposited thereon, so that no clearly defined compositional interfaces exist between the substrate and the layers, or between the layers.

Claim 3

An article according to claim 1 wherein the intermediate layer is 2-10 microns thick.

Claim 4

An article according to claim 1 wherein the first outer layer is 0.5-20 microns thick.

Claim 5

An article according to claim 3 wherein the first outer layer is 2-10 microns thick.

Claim 6

An article according to claim 1 wherein the first outer layer comprises a graded composite ceramic material comprising a continuous layer of alumina or zirconia having dispersed therein discontinuous discrete particles of at least one material different therefrom and selected from the group consisting of alumina, zirconia, and yttria.

Claim 7

An article according to claim 5 wherein the first outer layer is 0.5-20 micron thick; and further comprising an adherent, continuous, fully dense second outer layer about 0.5-900 microns thick, over and chemi­cally bonded to the first outer layer, of a graded composite ceramic material different from that of the first outer layer and comprising a continuous layer of alumina, zirconia, or yttria having dispersed therein discontinuous discrete particles of at least one material different therefrom and selected from the group consist­ing of alumina, zirconia, and yttria.

Claim 8

An article according to claim 6 wherein the second outer layer is 0.5-20 microns thick; and further comprising an adherent, continuous, fully dense addi­tional outer layer about 0.5-900 microns thick over and chemically bonded to the second outer layer, of alumina, zirconia, yttria stabilized zirconia, or yttria.

Claim 9

An article according to claim 1 wherein the first outer layer is 0.5-20 microns thick; and further comprising an adherent continuous, fully dense additional outer layer about 0.5-900 microns thick, over and chemi­cally bonded to the first outer layer, of alumina, zirconia, yttria stabilized zirconia, or yttria.

Claim 10

A coated article comprising: a fully dense shaped substrate body of a silicon nitride- or silicon carbide-based monolithic or composite material; an adherent, continuous, fully dense intermediate layer about 2-10 microns thick of an aluminum nitride material over and chemically bonded to the substrate body; an adherent, continuous, fully dense first outer layer about 2-10 microns thick comprising a continuous layer of alumina having dispersed therein discontinuous discrete particles of zirconia, over and chemically bonded to the intermediate layer; an adherent, continuous, fully dense second outer layer about 2-10 microns thick comprising a continuous layer of zirconia having dispersed therein discontinuous discrete particles of alumina over and chemically bonded to the first outer layer; an adherent, continuous, fully dense additional outer layer about 1-5 microns thick of zirconia, over and chemically bonded to the second outer layer; wherein each layer is a graded layer changing in composition from the material over which it is deposited to the material of the layer and further to the material, if any, deposited thereon, so that no clearly defined compositional interfaces exist between the substrate and the layers, or between the layers.

Claim 11

A coated article comprising: a fully dense shaped substrate body of a silicon nitride- or silicon carbide-based monolithic or composite material; an adherent, continuous, fully dense intermediate layer about 2-10 microns thick of an aluminum nitride material over and chemically bonded to the substrate body; an adherent, continuous, fully dense first outer layer about 2-10 microns thick comprising a continuous layer of alumina having dispersed therein discontinuous discrete particles of zirconia, over and chemically bonded to the intermediate layer; an adherent, continuous, fully dense second outer layer about 2-10 microns thick comprising a continuous layer of zirconia having dispersed therein discontinuous discrete particles of alumina over and chemically bonded to the first outer layer; an adherent, continuous, fully dense additional outer layer about 1-5 microns thick of zirconia, over and chemically bonded to the second outer layer; wherein each layer is a graded layer changing in composition from the material over which it is deposited to the material of the layer and further to the material, if any, deposited thereon, so that no clearly defined compositional interfaces exist between the substrate and the layers, or between the layers.

Claim 12

A process for depositing a high temperature stress and oxidation resistant coating on a silicon nitride- or silicon carbide-based substrate body compris­ing the steps of: passing over the substrate, at a temperature of about 900-1500°C and at a pressure between about 1 torr and about ambient pressure, a gaseous mixture comprising one or more halide vapors with other suitable reactant gases, and optionally a carrier gas, and at partial pressure ratios, at flow rates, and for times sufficient to deposit a continuous, fully dense, adherent coating; and gradually varying the halide vapors and other suitable reactant gases during the deposition of the coating in such a way that the coating is a graded coating comprising at least two adherent layers, each de­posited as a graded layer changing in composition from the material over which it is deposited to the material of the layer and further to the material, if any, de­posited thereon, so that no clearly defined compositional interfaces exist between the substrate and the layers, or between the layers; wherein the vapors and gases and their partial pressures are varied according to a predetermined time schedule and the halide vapors and other suitable reac­tant gases are selected so that the at least two layers comprise: an adherent, continuous intermediate layer about 0.5-20 microns thick of an aluminum nitride or aluminum oxynitride material, over and chemically bonded to the substrate body; and an adherent, continuous first outer layer about 0.5-900 microns thick comprising an oxide of aluminum or zirconium over and chemically bonded to the intermediate layer.

Claim 13

A process for depositing a high temperature stress and oxidation resistant coating on a silicon nitride- or silicon carbide-based substrate body compris­ing the steps of: passing over the substrate, at a temperature of about 900-1500°C and at a pressure between about 1 torr and about ambient pressure, a gaseous mixture comprising one or more halide vapors with other suitable reactant gases, and optionally a carrier gas, and at partial pressure ratios, at flow rates, and for times sufficient to deposit a continuous, fully dense, adherent coating; and gradually varying the halide vapors and other suitable reactant gases during the deposition of the coating in such a way that the coating is a graded coating comprising at least two adherent layers, each de­posited as a graded layer changing in composition from the material over which it is deposited to the material of the layer and further to the material, if any, de­posited thereon, so that no clearly defined compositional interfaces exist between the substrate and the layers, or between the layers; wherein the vapors and gases and their partial pressures are varied according to a predetermined time schedule and the halide vapors and other suitable reac­tant gases are selected so that the at least two layers comprise: an adherent, continuous intermediate layer about 0.5-20 microns thick of an aluminum nitride or aluminum oxynitride material, over and chemically bonded to the substrate body; and an adherent, continuous first outer layer about 0.5-900 microns thick comprising an oxide of aluminum or zirconium over and chemically bonded to the intermediate layer.

Claim 14

A process according to claim 10 wherein the step of gradually varying the vapors and gases includes selecting the predetermined time schedule and the vapors and gases and their partial pressures so that the first outer layer comprises a graded composite ceramic material comprising a continuous layer of alumina or zirconia having dispersed therein discontinuous discrete particles of at least one material different therefrom and selected from the group consisting of alumina, zirconia, and yttria.

Claim 15

A process according to claim 10 wherein the step of gradually varying the vapors and gases includes selecting the predetermined time schedule and the vapors and gases and their partial pressures so that the first outer layer is 0.5-20 microns thick; and so that the at least two layers further comprise an adherent, continuous second outer layer about 0.5-900 microns thick, over and chemically bonded to the first outer layer, of a graded composite ceramic material different from that of the first outer layer and comprising a continuous layer of alumina, zirconia, or yttria having dispersed therein discontinuous discrete particles of at least one material different therefrom and selected from the group consist­ing of alumina, zirconia, and yttria.

Claim 16

A process according to claim 12 wherein the step of gradually varying the vapors and gases includes selecting the predetermined time schedule and the vapors and gases and their partial pressures so that the second outer layer is 0.5-20 microns thick; and so that the at least two layers further comprise an adherent, continuous additional outer layer about 0.5-900 microns thick, over and chemically bonded to the second outer layer, of alumina, zirconia, yttria stabilized zirconia, or yttria.

Claim 17

A process according to claim 10 wherein the step of gradually varying the vapors and gases includes selecting the predetermined time schedule and the vapors and gases and their partial pressures so that the first outer layer is 0.5-20 microns thick; and so that the at least two layers further comprise an adherent, continuous additional outer layer about 0.5-900 microns thick, over and chemically bonded to the first outer layer, of alumina, zirconia, yttria stabilized zirconia, or yttria.