Method for preparing Si3N4 gradient material through self-diffusion

Abstract

The invention discloses a method for preparing a Si3N4 gradient material through self-diffusion. The method comprises steps as follows: Si3N4 and MO2 powder are taken as raw materials, wherein M is Ti, Zr or Hf, MgO-Re2O3 is taken as a sintering aid, the components are mixed and dried, and mixed powder is obtained; after the mixed powder is subjected to isostatic cool pressing, a sample is embedded in the powder, the mixture is put in a sintering furnace, and the Si3N4 gradient material is obtained finally. A gradient MN layer is formed on the surface of the Si3N4 material prepared with the method, and MN as a high-hardness and wear-resistant conductive phase can allow direct coating treatment on the surface of Si3N4 ceramic while improving surface hardness and wear resistance of the Si3N4ceramic; relative density is higher than 95%, surface hardness is 18-25 GPa, fracture toughness is 10-14 MPa.m<1 / 2>, bending strength is 1000-1500 Mpa, and gradient layer thickness is 10-200 mu m.

Description

technical field [0001] The invention relates to the technical field of non-oxide ceramic matrix composite materials, in particular to a method for preparing Si by self-diffusion 3 N 4 Gradient material method. Background technique [0002] Si 3 N 4 As a structural material, ceramic materials have excellent mechanical properties, such as high hardness, high strength, wear resistance, high temperature resistance, etc., and can be widely used in bearings, high-speed cutting tools, armor, etc., but in extremely high temperature and high-speed cutting It is still easy to wear under harsh conditions such as Si 3 N 4 Ceramics can usually be prepared as gradient materials, or they can be treated with PVD or CVD coating. [0003] At present, the preparation of gradient materials is mainly through sintering materials with different formulas or different raw materials to achieve different properties of surface layer and hardness. However, due to the difference in composition and ...

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Problems solved by technology

[0002] Si 3 N 4 As a structural material, ceramic materials have excellent mechanical properties, such as high hardness, high strength, wear resistance, high temperature resistance, etc., and can be widely used in bearings, high-speed cutting tools, armor, etc., but in extremely high temperature and high-speed cutting It is still easy to wear under harsh conditions such as Si 3 N 4 Ceramics can usually be used to prepare gradient materials, or to process them with PVD or CVD coatings

[0003] At present, the preparation of gradient materials is mainly through sintering materials with different formulas or different raw materials to achieve different properties of surface layer and hardness. However, due to the difference in composition and structure between the surface layer and core materials, the bonding force Weaker, and some even detach from the surface layer and the core during the sintering process, which greatly weakens the application of gradient materials; similarly, when using PVD and CVD technologies for non-conductive materials, it is necessary to cover the surface of the material with a However, there is still a problem of insufficient bonding between the substrate and the conductive layer, and PVD and CVD technologies often have the defect that the coating is too thin and the protective effect is not good.

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