A kind of composite gradient coating and preparation method thereof

Abstract

The invention discloses a preparation method of a composite gradient coating layer. A tungsten-contained substrate is pretreated; raw materials containing yttrium, tungsten and molybdenum are mixed toform pulp after ball milling; the pulp is uniformly coated on the surface of the tungsten-contained substrate, is dried, is heated in hydrogen, and is cooled to take out to form the tungsten-contained substrate with a tungsten molybdenum composite layer on the surface; the tungsten-contained substrate with the tungsten molybdenum composite layer on the surface is totally embedded in a crucible with a silication penetrating agent; then, the crucible is put in an atmospheric furnace; inertia gas is introduced for heat treatment; and the composite gradient coating layer on the surface of the tungsten-contained substrate is obtained by taking out after cooling. The preparation method is simple, can effectively improve the bonding force between the coating layer and the basal body and betweencoating layers, and greatly improves high-temperature oxidation resistance and thermal shock resistance of the substrate of the prepared composite gradient coating layer. The invention further relatesto the composite gradient coating layer obtained through the method.

Description

technical field [0001] The invention relates to a composite gradient coating and a preparation method thereof, belonging to the technical field of high-temperature coatings. Background technique [0002] Refractory metals are widely used as high-temperature components because of their high melting point, high-temperature mechanical properties, and excellent electrical and thermal conductivity, especially in aerospace applications. However, in the atmospheric environment, for example, niobium will undergo "pest" oxidation above 600°C, and tungsten will also begin to oxidize rapidly at around 700°C, which greatly reduces the service life, and also pollutes the environment and endangers human health. Refractory metals can only be used under the protection of an inert or reducing atmosphere, which greatly limits its application. [0003] At present, it is more common practice to coat various refractory metal surfaces with high-temperature anti-oxidation coatings for protection....

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Problems solved by technology

Patent CN106894021A combines the vacuum impregnation method with the coating technology to prepare a boron carbide-tungsten carbide coating on the surface of the tungsten material. The coated tungsten material has excellent mechanical properties, high temperature resistance and corrosion resistance, but usually The coating obtained by the coating method has poor bonding during use and poor thermal shock resistance

[0004] Patent CN105385987A uses the in-situ reaction method of molybdenum + nitriding + silicidation on the surface of metal tungsten to prepare a high-temperature anti-oxidation coating, but on the one hand, this method uses two embedding methods to easily form microcracks between layers, especially at high temperatures. Provide channels for the diffusion of oxygen. On the other hand, the thickness of the molybdenum layer obtained by the molybdenumization process is small, which affects the bonding strength between the coating and the substrate, and easily leads to insufficient thickness of the final effective high-temperature anti-oxidation layer, which is also not conducive to its thermal shock resistance. The plan also needs to include a longer period of nitriding treatment to prevent Si from excessive inward diffusion. The entire preparation method has many steps, long processing time, high energy consumption, and low production efficiency.

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