Niobium alloy surface Ni-Cr oxidation-resistant coating and preparation method thereof

Abstract

The invention relates to a niobium alloy surface Ni-Cr oxidation-resistant coating and its preparation method, and belongs to the field of a metal surface coating material and its preparation technology. The coating provided by the invention is composed of 30-40 wt% of Cr, 5-10 wt% of a niobium alloy and the balance Ni. The preparation method comprises the following steps: firstly, electroplating Ni on the surface of the niobium alloy; then, electroplating Cr; and finally, carrying out surface alloying by pulse YAG laser so as to obtain a Ni-Cr coating which is in complete metallurgical bonding to a matrix. By controlling thickness of the electroplated Ni layer and the electroplated Cr layer as well as the pulse YAG laser surface alloying technology, ingredients and thickness of the coating can be flexibly controlled. As content of Cr in the coating reaches 30-40 wt%, the coating has excellent resistance to high temperature oxidation.

Description

technical field [0001] The invention relates to a Ni-Cr anti-oxidation coating on the surface of a niobium alloy and a preparation method thereof, belonging to the technical field of metal surface coating materials and preparation thereof. Background technique [0002] Niobium alloy materials have good high-temperature strength and processing plasticity, and have become important high-temperature structural materials widely used in aviation, aerospace, nuclear industry and other fields. Severe oxidation occurs, which seriously restricts its application. At present, there are two main ways to improve the high-temperature oxidation resistance of niobium alloys: alloying and preparing anti-oxidation coatings on the surface. The alloying approach adds Ti, Al, Cr, Si and other elements to the niobium-based alloy, so that the alloy can self-generate an oxide protective film in high-temperature applications, thereby improving its oxidation resistance. This method usually sacrifice...

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Problems solved by technology

For example, Chinese patent ZL200710192652.X discloses a method for preparing a niobium alloy high-temperature oxidation-resistant silicide coating. First, a 50-80 μm thick molybdenum layer is prepared by vacuum slurry sintering (sintering temperature 1450-1550 ° C), and then MoSi2 coating was prepared by infiltration and siliconization under air protection (infiltration temperature 1200-1300°C); patent application 201210237037.7 discloses a low-density niobium alloy high-temperature oxidation-resistant material and a method for preparing a high-temperature oxidation-resistant coating. Coating slurry of various alloying elements such as , Ti, Mo, etc. is coated on the substrate, and melted and fired for 10-30 minutes at a temperature of 1200-1350°C and a vacuum degree greater than 1×10-1Pa to obtain a high-temperature anti-oxidation Coating; Chinese patent ZL200710165074.0 discloses a high-temperature anti-oxidation material and coating preparation method, by coating the coating slurry containing Al, MoSi2, Ni, Mo, etc. on the substrate, at a temperature of 1350 ~ Melting at 1650°C and a vacuum greater than 1×10-1Pa for 5 to 30 minutes to form a high-temperature anti-oxidation coating with a thickness of 50-140 microns; In the application, it is sometimes necessary to use copper-based, palladium-based and other solders to achieve sealing with sapphire, stainless steel and other materials, and the anti-oxidation coating on the surface of the niobium alloy is required to cover the brazing area (brazing temperature is about 1000 ° C), therefore, The temperature required for coating preparation cannot exceed 1000°C, thus limiting the application of the above-mentioned silicide coatings, such as thermionic fuel elements for space thermionic reactor power supplies

The surface of Ni-Cr alloy can form a thermodynamically stable and dense Cr2O3 oxide film at high temperature, which can be used for high-temperature anti-oxidation coatings used at 600-1100 ° C. The preparation methods of Ni-Cr alloy coatings mainly include electroplating and thermal spraying. There are many pores in the coating, which provide a channel for the diffusion of oxygen atoms, which affects the oxidation resistance of the coating. At the same time, the bonding force between the coating and the substrate is poor, and the coating is easy to peel off; The use temperature of the layer is low and the cost is high, which is also limited in practical applications

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