Thermal shock damage characteristics of refractory composites

The thermal shock damage characteristics of refractory composites are closely related to the rapid temperature changes they are subjected to during use. This temperature change will cause a large temperature gradient and thermal stress inside the material, which will in turn trigger a series of damage phenomena. The following is a detailed analysis of the thermal shock damage characteristics of refractory composites:

I. Types of thermal shock damage

The thermal shock damage of refractory materials can be divided into two categories:

Instantaneous fracture (thermal shock fracture):

When refractory materials are suddenly exposed to extremely high or extremely low temperature environments, huge thermal stress will be generated due to the inconsistent thermal expansion or contraction of various parts of the material.

If this thermal stress exceeds the inherent strength of the material, it will cause the material to break instantly, which is the so-called "thermal shock fracture".

Thermal shock damage (thermal fatigue damage):

Under the action of multiple thermal shock cycles, cracks and peeling will gradually appear on the surface of the refractory.

With the expansion of cracks and the peeling of materials, the overall performance of the material will gradually decline, which may eventually lead to overall damage.

II. Specific manifestations of thermal shock damage

Crack generation and expansion:

Under the action of thermal shock, a large number of microcracks will be generated inside the refractory. These cracks will gradually expand under the action of thermal stress to form a larger crack network.

The expansion of cracks will further aggravate the damage of the material and reduce its performance.

Spalling and fragmentation:

As the cracks expand and the thermal stress of the material is concentrated, part of the material may peel off from the matrix.

In extreme cases, the entire refractory composite may break into multiple small pieces, completely losing its original structure and performance.

Performance degradation:

Thermal shock not only causes changes in the physical structure of the refractory material, but also has a significant impact on its mechanical properties, thermal properties, etc.

For example, the performance parameters such as flexural strength and elastic modulus of the material may decrease significantly after thermal shock.

III. Influencing factors

The thermal shock damage characteristics of refractory composites are affected by many factors, mainly including:

Material properties:

The physical properties of the material such as thermal expansion coefficient, elastic modulus, thermal conductivity, etc. have an important influence on its thermal shock resistance.

For example, materials with a smaller thermal expansion coefficient generate less thermal stress when the temperature changes, so they have better thermal shock resistance.

Microstructure:

The microstructure of the material (such as grain size, phase composition, porosity, etc.) will also affect its thermal shock resistance.

Appropriate porosity can alleviate the phenomenon of thermal stress concentration and improve the thermal shock resistance of the material.

Use environment:

The use environment of refractory materials (such as temperature fluctuation range, frequency, etc.) is also an important factor affecting its thermal shock resistance.

Refractory materials used in environments with large temperature fluctuations need to have higher thermal shock resistance.

4. Methods to improve thermal shock resistance

In order to improve the thermal shock resistance of refractory composites, the following measures can be taken:

Optimize material formulation:

Optimize its physical properties and microstructure by adjusting the chemical composition and phase composition of the material.

Introduce reinforcement phase:

Add an appropriate amount of reinforcement phase (such as fiber, whisker, etc.) to the material to improve its fracture toughness and thermal shock resistance.

Control porosity:

Control the porosity of the material by adjusting the production process to alleviate the phenomenon of thermal stress concentration and improve thermal shock resistance.

Use advanced preparation technology:

Use advanced preparation technology (such as isostatic pressing, hot pressing sintering, etc.) to prepare refractory composites with better performance.

In summary, the thermal shock damage characteristics of refractory composites are mainly manifested in crack generation and expansion, spalling and fragmentation, and performance degradation. By optimizing material formula, introducing reinforcement phase, controlling porosity, and using advanced preparation technology, its thermal shock resistance can be effectively improved.