Mo-C-N-Si-Nb gradient coating material and preparation method thereof

Abstract

The invention discloses Mo-C-N-Si-Nb gradient coating material and a preparation method thereof. One side or two sides of Mo-Nb alloy are provided with composite coatings. The composite coatings are gradient coatings with Si, C and N content gradually increasing and Mo and Nb content gradually decreasing from inside to outside along the Mo-Nb alloy direction. The gradient coatings are tightly combined with a base. The gradient coatings are high in bending strength. Steady-state creep rate of base material is 3 levels lower than that of pure Mo monocrystal. The surface of the coatings has high silicon content. The surface layers of the coatings are mainly made from, MoSi2, SiC, Si3N4 and Si, the middle layers of the coatings are mainly made from MoSi2, SiC and Si3N4, and transition layers of the coatings are mainly made from Mo5Si3, MoSi3 and a trace of NbSi2. No cryogenic pulverization occurs in low-temperature oxidation experiment at 500 DEG C, and the coatings are high in high-temperature oxidation resistance. The preparation method has the advantages that the formation speed of gradient layers is high, the preparation time is short, and the thickness of the coatings is free to control. The Mo-C-N-Si-Nb gradient coating material has the advantages of compact surface structure, fine high-temperature creep resistance, fine high-temperature oxidation resistance and the like.

Description

technical field [0001] The invention relates to a gradient coating material and a preparation method thereof, in particular to a Mo-C-N-Si-Nb gradient coating material and a preparation method thereof. Background technique [0002] The crystal orientation is < 111 > Mo-Nb alloy (molybdenum-niobium alloy) has very high heat resistance, and can be applied to structural parts with a working temperature of 1600 ° C. It has excellent corrosion resistance, shock resistance, and thermal conductivity in various media. It has high electrical conductivity and good machinability. At 1500°C and 10MPa, the steady-state creep rate of Mo-3Nb (3 is the mass percent) alloy single crystal is 3 orders of magnitude lower than that of pure Mo single crystal, which greatly improves the high temperature creep resistance of the material and has a high high temperature strength. It is widely used as the emitter in space thermionic reactors, missile exhaust nozzles, satellite rocket propeller...

AI Technical Summary

Problems solved by technology

Li Yungang et al. successfully prepared Mo-MoSi on molybdenum substrate by molten salt electrodeposition silicon infiltration. 2 Functionally graded material, and obtained the invention patent, this method is used in the preparation of Mo-MoSi with gradient layer thickness of 80 μm ~ 110 μm 2 Functionally graded materials have the characteristics of easy control of gradient layer thickness, wide control range of process parameters, easy operation, compact and smooth material surface structure, etc. However, due to the low preparation temperature of this method, the small concentration gradient of Si in the matrix, and the diffusion The speed is slow, resulting in the preparation of Mo-MoSi with a gradient layer thickness greater than 200 μm 2 It takes a long time when functionally graded materials

[0009] The above analysis shows that there is no Mo-C-N-Si-Nb gradient coating material and its preparation method at present, even in the preparation of pure MoSi similar to this material 2 The coating material also has the following deficiencies: (1) The coating material has many defects such as pores and voids, the mechanical properties and high temperature oxidation resistance are relatively poor, and the service life of the material is short (2) The process conditions are complex and the production High cost, easy to produce toxic gas, pollute the environment

(3) Composite high-temperature coatings with high silicon content on the alloy surface cannot be prepared during the preparation process

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