The excellent oxidation resistance of tungsten cemented carbide balls is primarily due to their material properties and optimized composition.
1. Material Properties Lay the Foundation for Oxidation Resistance
Tungsten cemented carbide balls are manufactured through a powder metallurgy process, using a high-hardness ceramic phase such as tungsten carbide (WC) as a skeleton and a metal such as cobalt (Co) as a binder phase. This structure provides the following oxidation resistance advantages:
1. High-Temperature Stability
The WC ceramic phase has a melting point of up to 2870°C, maintaining structural stability at high temperatures and reducing active sites for oxidation reactions. Although the Co binder phase begins to oxidize at approximately 200°C, this oxidation process can be significantly slowed through composition optimization.
2. Dense Oxide Film Formation
In the initial oxidation stages, a dense oxide film (such as CoO and Co?O?) forms on the carbide surface, effectively blocking further oxygen penetration and reducing the oxidation rate.
II. Composition Optimization to Improve Oxidation Resistance
The oxidation resistance of tungsten cemented carbide balls can be further enhanced by adding specific elements or adjusting the binder phase composition:
1. Ruthenium (Ru) Doping
Research has shown that adding Ru significantly improves the oxidation resistance of cemented carbide: Ru dissolves in Co, hindering the diffusion of oxygen atoms and increasing the oxidation activation energy.
2. Rare Earth Element Addition
Rare earth elements (such as yttrium and lanthanum) refine grains, purify grain boundaries, strengthen the bond between the oxide film and the substrate, and reduce oxide film flaking, thereby extending the oxidation resistance life.
III. Testing the Oxidation Resistance of Tungsten Cemented Carbide Balls
The oxidation resistance of tungsten cemented carbide balls can be scientifically evaluated using the following methods:
1. Thermogravimetric Analysis (TGA)
Principle: The sample is heated in an oxygen-containing atmosphere (e.g., 19% to 23% O? + N?), the mass change is monitored, and the oxidation rate is calculated.
Advantage: Accurate data is generated, allowing for comparison of the oxidation resistance of different materials. 2. Oxide Layer Thickness Measurement
Method: After the oxidation test, measure the oxide layer thickness using a scanning electron microscope (SEM) or metallographic microscope.
Significance: The thinner the oxide layer, the stronger the oxidation resistance.
IV. Practical Applications of Tungsten Cemented Carbide Balls Oxidation Resistance
The excellent oxidation resistance of tungsten cemented carbide balls makes them outstanding in the following areas:
1. High-Temperature Processing Environments
In high-temperature friction environments such as metal cutting and milling, tungsten cemented carbide balls can maintain surface stability, reduce wear and dimensional change caused by oxidation, and extend tool life.
2. Corrosive Media Applications
In corrosive environments such as acids and alkalis, the oxidation resistance and corrosion resistance of tungsten cemented carbide balls work synergistically to ensure long-term stable performance.
3. Precision Equipment Components
The high hardness and oxidation resistance of tungsten cemented carbide balls make them an ideal material for precision bearings, valves, and other components, ensuring reliable operation of equipment in high temperatures or harsh environments.
