As we all know, metals have good toughness and mechanical properties, but they have poor chemical stability at high temperatures and are prone to oxidation. Ceramics can withstand high temperature and have good chemical stability, but are brittle and have poor mechanical shock resistance. As a high-temperature composite material, cermets are also quite "hard-core" in performance. They take into account the high toughness and plasticity of metals and the high melting point, corrosion Ceramic Part resistance and wear resistance of ceramics. They are used in aerospace, temperature measurement, nuclear energy It has broad application prospects in the fields of processing and manufacturing. It can be said that cermet is an advanced high-temperature structural material with comprehensive properties of metal and ceramics. At present, the specific application objects mainly include high-temperature wear-resistant parts, temperature measuring components, high-temperature coatings, high-speed cutting tools, stamping dies, etc.
Definition
Cermet belongs Metallized Alumina Ceramic to a kind of high temperature composite material, which is related and different from metal matrix composite material and ceramic matrix composite material, so it is difficult to define accurately. The definition of cermet given by some researchers is: a heterogeneous composite material composed of a metal or alloy and one or several ceramics, of which ceramics account for 15% to 85% (volume fraction), at the preparation temperature. Metals and ceramics are less soluble, do not chemically react with each other, or are limited to slight chemical reactions and diffusion penetration on the surface. In addition, some relevant workers have classified "tungsten carbide" into "cermet". From the perspective of material composition, this view is also reasonable.
Preparation principles of cermets
In order to better disperse and combine with metal, the non-metallic phase (ceramic) in cermet is usually close to equiaxed fine particles, and the particle size is generally 1-100 μm. The success of cermet preparation depends on whether a "binder" that can wet and bond its ceramic and metal components can be generated during the preparation process, and this "binder" can pass through the ceramics. Diffusion produces a finite solid solution. If the "formed binder" chemically reacts strongly with the ceramic, it can have undesirable consequences, resulting in reduced material properties because the reaction produces usually brittle intermetallic compounds. In the process of sintering preparation, the following four factors have a decisive influence on the properties of cermets: (1) the physical and chemical Alumina Ceramic Rod properties of metals and ceramics, including expansion coefficient, thermal conductivity, elastic modulus and plasticity of metal materials;
(2) The extent to which metal wets the ceramic;
(3) The phase and structural characteristics of metals and ceramics, including phase distribution, grain size and shape, and phase continuity, etc., similar crystal structures, lattice constants and bonding types help form solid solutions;
(4) The degree of reaction between metal and ceramic during high temperature preparation.
Classification and application
According to the type of main non-metallic Alumina Ceramic Parts phase in cermets, cermets can be divided into five types: oxide-based, carbide-based, carbonitride-based, boride-based and cermets containing graphite or diamond-like carbon.
What is cermet?
2022 08/16