What is the ablation mechanism of carbon rods under high arc temperature? How to extend the service life through material modification?

What is the ablation mechanism of carbon rods under high arc temperature? How to extend the service life through material modification?

The ablation of carbon rods under high temperature of arc is a complex process involving multiple physical and chemical changes. Material modification can effectively improve the performance of carbon rods and extend their service life. The following is a specific analysis of the ablation mechanism and material modification methods:

Ablation mechanism

High temperature evaporation: The high temperature generated by the arc can rapidly increase the surface temperature of the carbon rod to above the boiling point of carbon, causing carbon to evaporate directly from solid to gaseous state. This will cause the surface material of the carbon rod to gradually lose and the size to become smaller.

Oxidation reaction: In the high temperature environment of the arc, oxygen in the air reacts with carbon to produce gases such as carbon monoxide and carbon dioxide. The oxidation reaction will continuously consume the carbon rod material, causing pits and cracks to form on the surface of the carbon rod, accelerating the damage of the carbon rod.

Arc erosion: The plasma in the arc has the characteristics of high energy and high-speed movement, which will have a strong impact and erosion on the surface of the carbon rod. This erosion will destroy the structure of the surface of the carbon rod, causing carbon particles to be peeled off, resulting in ablation of the carbon rod.

Thermal stress damage: Thermal stress will be generated inside the carbon rod at high temperature of the arc. Since different parts of the carbon rod are heated unevenly and the thermal stress distribution is uneven, when the thermal stress exceeds the bearing limit of the carbon rod material, it will cause cracks or even breakage in the carbon rod, accelerating the ablation process.

Material modification method

Adding antioxidants: Adding antioxidants such as rare earth oxides and borides to the carbon rod material can form a dense protective film on the surface of the carbon rod, preventing oxygen from contacting carbon and slowing down the oxidation reaction. For example, adding yttrium oxide (Y₂O₃) can improve the antioxidant properties of the carbon rod and extend its service life under high-temperature arcs.

Optimizing the degree of graphitization: Increasing the degree of graphitization of the carbon rod can make the crystal structure of the carbon rod more regular and reduce defects, thereby improving its high-temperature resistance and strength. By optimizing the graphitization process parameters, such as increasing the temperature and extending the insulation time, a carbon rod with a higher degree of graphitization can be obtained, which reduces its ablation rate under high arc temperatures.

Use composite reinforcement materials: Adding reinforcement materials such as carbon fiber and silicon carbide (SiC) particles to the carbon rod can improve the mechanical strength and thermal conductivity of the carbon rod. Carbon fiber can enhance the toughness of the carbon rod and enhance its ability to resist arc erosion and thermal stress damage; SiC particles can improve the hardness and high temperature resistance of the carbon rod and reduce high temperature evaporation and oxidation.

Surface coating treatment: Coat the surface of the carbon rod with a layer of high temperature resistant and oxidation resistant coating, such as boron nitride (BN) coating, aluminum oxide (Al₂O₃) coating, etc. These coatings can effectively isolate the carbon rod from contact with high temperature arc and oxidizing gas, and play a role in protecting the carbon rod. At the same time, the coating can also improve the smoothness of the carbon rod surface and reduce arc erosion.