The difference between graphite material and metal is that its elastic modulus is relatively low. Graphite material is basically a brittle material, which is prone to brittle fracture at room temperature. Graphite products with larger bulk density have larger elastic moduli and are directional. For extruded products, the elastic modulus of parallel extrusion direction is larger than that of vertical extrusion.
By measuring the modulus of elasticity of graphite products, we can infer their high temperature properties and understand their thermal shock resistance. It is generally believed that the smaller the elastic modulus of graphite products is, the better its thermal resistance is.
The modulus of elasticity of graphite products generally increases with the increase of experimental temperature, and the range of increase varies with the quality.
Graphite is the most wearable material because graphite has high adhesion to all kinds of materials. High-purity graphite crystals are easy to peel off along the crystal plane. When the graphite device is between two friction surfaces, the friction coefficient decreases remarkably due to the formation of a very thin graphite crystal film. The friction coefficient of graphite to various materials at 20℃ is shown in the table below.
Friction couple | Test temperature | Atmosphere | Static friction coefficient | Dynamic friction coefficient |
Graphite to Graphite | 25 2450 | Air Helium | 0.35 0.65 | 0.35 0.65 |
High strength graphite to High strength graphite | 25 2450 | Air Helium | 0.33 0.70 | 0.24 0.28 |
High strength graphite to Surface polished steel | 28 | Air | 0.35 | |
Graphite to Metal Gold Silver Copper Zinc | 25 25 25 25 | Air Air Air Air | 0.26 0.31 0.30 0.37 |