A method for forming an oxidation protection system on a composite structure may comprise: applying a ceramic layer slurry to the composite structure, wherein the ceramic layer slurry comprises aluminum and silicon in a solvent or carrier fluid; and heating the composite structure in an environment comprising nitrogen gas and oxygen gas to form a ceramic layer on the composite structure, wherein the ceramic layer comprises aluminum nitride and alumina.

A method for forming an oxidation protection system on a composite structure may comprise: applying a ceramic layer slurry to the composite structure, wherein the ceramic layer slurry comprises aluminum and silicon in a solvent or carrier fluid; and heating the composite structure in an environment comprising nitrogen gas and oxygen gas to form a ceramic layer on the composite structure, wherein the ceramic layer comprises aluminum nitride and alumina.

A surface-coated boron nitride sintered body tool is provided, in which at least a cutting edge portion includes a cubic boron nitride sintered body and a coating film formed on a surface of the cubic boron nitride sintered body. The coating film includes an A layer and a B layer. The A layer is formed of columnar crystals each having a particle size of 10 nm or more and 400 nm or less. The B layer is formed of columnar crystals each having a particle size of 5 nm or more and 70 nm or less. The B layer is formed by alternately stacking two or more compound layers having different compositions. The compound layers each have a thickness of 0.5 nm or more and 300 nm or less.

A surface-coated boron nitride sintered body tool is provided, in which at least a cutting edge portion includes a cubic boron nitride sintered body and a coating film formed on a surface of the cubic boron nitride sintered body. The coating film includes an A layer and a B layer. The A layer is formed of columnar crystals each having a particle size of 10 nm or more and 400 nm or less. The B layer is formed of columnar crystals each having a particle size of 5 nm or more and 70 nm or less. The B layer is formed by alternately stacking two or more compound layers having different compositions. The compound layers each have a thickness of 0.5 nm or more and 300 nm or less.

A cBN sintered body has 40%-85% cBN by volume and 15% to 60% binder phase by volume. and inevitable impurities. The binder phase has an Al compound including Al and at least one element selected from N, O and B, and a Zr compound including Zr and at least one element selected from C, N, O and B. The Zr compound includes ZrO, or ZrO and ZrO.sub.2. In an X-ray diffraction, where a peak intensity of a (111) plane of the ZrO is I.sub.1, a peak intensity of a (101) plane of tetragonal ZrO.sub.2 is I.sub.2t and a peak intensity of a (111) plane of cubic ZrO.sub.2 is I.sub.2c, a ratio of the intensity of I.sub.1 to total intensities of I.sub.1, I.sub.2t and I.sub.2c is 0.6-1.0, and an average grain size of the Al compound is 80 nm-300 nm.

A cBN sintered body has 40%-85% cBN by volume and 15% to 60% binder phase by volume. and inevitable impurities. The binder phase has an Al compound including Al and at least one element selected from N, O and B, and a Zr compound including Zr and at least one element selected from C, N, O and B. The Zr compound includes ZrO, or ZrO and ZrO.sub.2. In an X-ray diffraction, where a peak intensity of a (111) plane of the ZrO is I.sub.1, a peak intensity of a (101) plane of tetragonal ZrO.sub.2 is I.sub.2t and a peak intensity of a (111) plane of cubic ZrO.sub.2 is I.sub.2c, a ratio of the intensity of I.sub.1 to total intensities of I.sub.1, I.sub.2t and I.sub.2c is 0.6-1.0, and an average grain size of the Al compound is 80 nm-300 nm.

A coated article, comprising an article having at least one surface having disposed thereupon an oxidation resistant coating comprising at least two constituents to form a composition, a first constituent comprising at least one thermal expansion component comprising at least about 10% by volume to up to about 99% by volume of the composition, a second constituent comprising at least one oxygen scavenger comprising at least about 1% by volume to up to about 90% by volume of the composition.

A coated article, comprising an article having at least one surface having disposed thereupon an oxidation resistant coating comprising at least two constituents to form a composition, a first constituent comprising at least one thermal expansion component comprising at least about 10% by volume to up to about 99% by volume of the composition, a second constituent comprising at least one oxygen scavenger comprising at least about 1% by volume to up to about 90% by volume of the composition.

A method of making a ceramic matrix composite that exhibits chemical resistance has been developed. The method comprises depositing a compliant layer comprising boron nitride, silicon-doped boron nitride, and/or pyrolytic carbon on silicon carbide fibers, depositing a barrier layer having a high contact angle with molten silicon on the compliant layer, and depositing a wetting layer comprising silicon carbide, boron carbide, and/or pyrolytic carbon on the barrier layer. After depositing the wetting layer, a fiber preform comprising the silicon carbide fibers is infiltrated with a slurry. After slurry infiltration, the fiber preform is infiltrated with a melt comprising silicon, and then the melt is cooled, thereby forming a ceramic matrix composite.

A composite article includes a substrate and a powder-derived composite coating on the substrate. The composite coating includes discrete regions of a first material and discrete regions of a second material. At least one of the first material or the second material is a chemical precursor.