Abstract: A ceramic coating for a metal article includes a metallic bond coat deposited on the metal article, at least one MCrAlY/ceramic layer deposited on the bond coat, and a ceramic composite top layer deposited on the MCrAlY/ceramic layer. The M in MCrAlY stands for Fe, Ni, Co, or a mixture of Ni and Co. The ceramic in the MCrAlY/ceramic layer comprises mullite, alumina, zircon, sillimanite, sodium zirconium phosphate, fused silica, cordierite, aluminum titanate, or zirconia. The ceramic composite top layer comprises a ceramic matrix and at least one secondary phase. A method of making the coating includes sequentially depositing a metallic bond coat on the metal article, at least one MCrAlY/ceramic layer on the bond coat, and a ceramic composite top layer on the MCrAlY/ceramic layer.

Abstract: A very thin abrasive material on a substrate is comprised of ceramic particulates contained within a metal matrix. The particulates extend fully through the matrix from the substrate surface to the machined free surface of the abrasive. In a representative 0.38 mm abrasive the particulates are sized normally at 0.42-0.50 mm and have an aspect ratio of less than 1.9 to 1. This enables a high density of particulates, in the range 33-62 per cm.sup.2, while at the same time ensuring good bonding in that most of the particulates are fully surrounded by matrix. When the abrasive is applied to the tip of a superalloy gas turbine engine blade, about 10-50% of the matrix metal is removed after machining. This allows the machined ceramic particulates to project into space and to thus better interact with ceramic abradable seals. In the preferred practice of the invention the particulates are alumina coated silicon carbide contained in a nickel superalloy matrix.

Abstract: A combination of sintering, plasma arc spraying, hot isostatic pressing and chemical milling is used to form an abrasive surface on an article. Alumina coated silicon carbide particulates are clad with nickel and sinter bonded to the surface of a superalloy turbine blade tip. An impermeable layer of plasma arc sprayed superalloy matrix is deposited over the particulates and then has its inherent voids eliminated by hot isostatic pressing. The abrasive material so formed on the surface is then machined to expose the particulates. Next, a portion of the matrix is removed so that the machined particulates project into space and are thus best enabled to interact with abradable ceramic air seals in a gas turbine engine. The ceramic particulates are sized so they are larger than the finished thickness of the abrasive and they have small aspect ratios. Thus, a high density spacing can be achieved while at the same time it is insured that matrix adequately surrounds the particles and holds them in place during use.

Abstract: Methods of coating metallic substrates with continuously graded metallic-ceramic material are disclosed. The method maintains low stress to strength ratios across the depth of the graded layer when the graded layer is under subsequent operative conditions. In one particular structure, the coating is applied to a metal substrate and includes a metallic bond coat a continuously graded metallic-ceramic layer and an outer layer of abradable ceramic material. Modulation of the metal substrate temperature during the coating process establishes a desired residual stress pattern in the graded layer.

Abstract: Structure coated with graded ceramic material and methods of coating application are disclosed. Techniques for maintaining low stress to strength ratios across the depth of the coating are discussed.In one particular structure the coating is applied to a metal substrate (12) and comprises a metallic bond coat (14), a first interlayer (16) of metal/ceramic material, a second interlayer (18) of metal/ceramic material having an increased proportion of ceramic and an all ceramic layer. Modulation of the metal substrate temperature during the coating process establishes a desired residual stress pattern in the part.

Abstract: Structure coated with graded ceramic material and methods of coating application are disclosed. Techniques for maintaining low stress to strength ratios across the depth of the coating are discussed. In one particular structure the coating is applied to a metal substrate (12) and comprises a metallic bond coat (14), a first interlayer (16) of metal/ceramic material, a second interlayer (18) of metal/ceramic material having an increased proportion of ceramic and an all ceramic layer. Modulation of the metal substrate temperature during the coating process establishes a desired residual stress pattern in the part.