WC - 12Co thermal sprayed coatings have gained significant popularity in various industrial applications due to their excellent wear resistance, high hardness, and good corrosion resistance. As a leading supplier of WC - 12Co thermal spraying materials, I have witnessed firsthand the remarkable performance of these coatings in protecting components from wear and extending their service life. In this blog, I will delve into the wear mechanism of WC - 12Co thermal sprayed coatings, exploring the factors that influence their wear behavior and the strategies to optimize their performance.
Structure and Properties of WC - 12Co Thermal Sprayed Coatings
WC - 12Co coatings are typically composed of tungsten carbide (WC) particles embedded in a cobalt (Co) matrix. The WC particles provide the coating with high hardness and wear resistance, while the Co matrix acts as a binder, holding the WC particles together and providing some ductility to the coating. The microstructure of WC - 12Co thermal sprayed coatings can vary depending on the spraying process, powder characteristics, and spraying parameters. Generally, the coatings consist of a mixture of WC particles, partially melted WC particles, and a Co - rich matrix.
The hardness of WC - 12Co coatings is mainly determined by the volume fraction and size of the WC particles. Higher WC content and smaller particle size usually result in higher hardness and better wear resistance. The Co matrix also plays an important role in the mechanical properties of the coating. A proper amount of Co can improve the toughness and adhesion of the coating, while excessive Co may reduce the hardness and wear resistance.
Wear Mechanisms of WC - 12Co Thermal Sprayed Coatings
Abrasive Wear
Abrasive wear is one of the most common wear mechanisms in WC - 12Co thermal sprayed coatings. It occurs when hard particles slide or roll over the coating surface, causing the removal of material. In abrasive wear, the WC particles in the coating act as hard asperities, resisting the penetration of the abrasive particles. The Co matrix provides support to the WC particles and helps to distribute the load.
The wear resistance of WC - 12Co coatings against abrasive wear depends on several factors. Firstly, the hardness and size of the WC particles are crucial. Smaller and harder WC particles can better resist the cutting action of the abrasive particles. Secondly, the volume fraction of WC also affects the wear resistance. Higher WC content generally leads to better abrasive wear resistance. Additionally, the hardness and toughness of the Co matrix play a role. A tougher Co matrix can prevent the WC particles from being pulled out easily, reducing the material loss.
Adhesive Wear
Adhesive wear occurs when two surfaces in contact slide against each other, causing the transfer of material between the surfaces. In the case of WC - 12Co coatings, adhesive wear can happen when the coating slides against a counter - surface. The Co matrix in the coating can adhere to the counter - surface, and the WC particles may be pulled out along with the adhered Co.
The adhesion between the coating and the counter - surface is influenced by the surface roughness, material properties, and contact pressure. A smoother surface of the coating can reduce the probability of adhesion. The chemical compatibility between the coating and the counter - surface also affects the adhesive wear. For example, if the counter - surface has a high affinity for Co, more material transfer may occur.
Erosive Wear
Erosive wear is caused by the impact of solid particles or liquid droplets on the coating surface. In erosive wear, the WC - 12Co coating is subjected to high - velocity impacts, which can cause the fragmentation and removal of the WC particles and the Co matrix.
The erosive wear resistance of WC - 12Co coatings is related to the impact angle, particle velocity, and particle size of the erodent. At low impact angles, the wear mechanism is mainly plowing and cutting, while at high impact angles, the wear is dominated by brittle fracture. The hardness and toughness of the coating are important factors in erosive wear. A coating with high hardness can resist the initial impact, while good toughness can prevent the propagation of cracks.
Corrosive Wear
Corrosive wear occurs when the coating is exposed to a corrosive environment while being subjected to mechanical wear. In a corrosive environment, the Co matrix in the WC - 12Co coating can be corroded, which weakens the bonding between the WC particles and the matrix. As a result, the WC particles are more easily removed during mechanical wear.
The corrosion resistance of WC - 12Co coatings depends on the chemical composition of the environment and the protective properties of the coating. Coatings with a more corrosion - resistant Co alloy or additional protective layers can improve the corrosion - wear resistance.
Factors Affecting the Wear Behavior of WC - 12Co Thermal Sprayed Coatings
Spraying Process
The spraying process used to deposit the WC - 12Co coating has a significant impact on its wear behavior. Different spraying processes, such as high - velocity oxygen - fuel (HVOF) spraying, plasma spraying, and detonation gun spraying, can produce coatings with different microstructures and properties.
HVOF spraying is widely used for depositing WC - 12Co coatings because it can produce coatings with high density, low porosity, and good adhesion. The high - velocity particles in HVOF spraying result in a well - bonded coating with a relatively fine microstructure, which generally leads to better wear resistance. Plasma spraying, on the other hand, can deposit coatings at a higher deposition rate, but the coatings may have higher porosity and lower density compared to HVOF - sprayed coatings.
Powder Characteristics
The characteristics of the WC - 12Co powder, such as particle size, shape, and composition, also affect the wear behavior of the coating. Smaller powder particles can result in a finer microstructure and higher hardness in the coating. Spherical powder particles are preferred because they can flow more easily during the spraying process and produce a more uniform coating.
The composition of the powder, especially the WC/Co ratio, is crucial. As mentioned earlier, a proper WC/Co ratio is necessary to balance the hardness and toughness of the coating. Some advanced powders may also contain additives to improve the performance of the coating, such as rare - earth elements to enhance the adhesion and corrosion resistance.
Service Conditions
The service conditions, including the load, sliding speed, temperature, and environment, have a direct influence on the wear behavior of WC - 12Co thermal sprayed coatings. Higher loads and sliding speeds usually increase the wear rate. At high temperatures, the mechanical properties of the coating may change, and the Co matrix may become softer, reducing the wear resistance.
In a corrosive environment, the combination of corrosion and wear can accelerate the material loss. For example, in a marine environment, the presence of saltwater can cause corrosion of the Co matrix, which in turn affects the wear resistance of the coating.
Strategies to Optimize the Wear Performance of WC - 12Co Thermal Sprayed Coatings
Material Selection
Choosing the right WC - 12Co powder is the first step in optimizing the wear performance of the coating. Consider the service conditions and the specific requirements of the application. For abrasive wear - dominated applications, a powder with high WC content and small particle size may be preferred. For applications with high impact loads, a powder with a proper balance of hardness and toughness should be selected.
We also offer related products such as WC - 10Ni Thermal Spray, Casting Tungsten Carbide, and MACROCRYTALLITE TUNGSTEN CARBIDE. These products have their own unique properties and can be used in different applications to meet various wear - resistance needs.
Process Optimization
Optimizing the spraying process parameters is essential to obtain a high - quality WC - 12Co coating. For HVOF spraying, parameters such as fuel - to - oxygen ratio, powder feed rate, and spraying distance need to be carefully controlled. A proper spraying distance can ensure that the particles are fully melted and deposited on the substrate with sufficient kinetic energy, resulting in a dense and well - bonded coating.
Post - Treatment
Post - treatment processes, such as heat treatment and surface finishing, can also improve the wear performance of WC - 12Co coatings. Heat treatment can relieve the residual stress in the coating and improve the bonding between the WC particles and the Co matrix. Surface finishing, such as grinding and polishing, can reduce the surface roughness, which is beneficial for reducing adhesive wear.
Conclusion
Understanding the wear mechanism of WC - 12Co thermal sprayed coatings is crucial for optimizing their performance in various industrial applications. Abrasive wear, adhesive wear, erosive wear, and corrosive wear are the main wear mechanisms that affect the service life of these coatings. By considering factors such as the spraying process, powder characteristics, and service conditions, and implementing appropriate strategies such as material selection, process optimization, and post - treatment, the wear resistance of WC - 12Co coatings can be significantly improved.
As a supplier of WC - 12Co thermal spraying materials, we are committed to providing high - quality products and technical support to our customers. If you are interested in our WC - 12Co thermal spraying materials or have any questions about wear - resistant coatings, please feel free to contact us for further discussion and procurement negotiation.
References
- Liu, Y., & Li, C. (2018). Wear behavior and mechanism of WC - Co coatings under different sliding conditions. Wear, 406 - 407, 161 - 169.
- Zhang, H., & Wang, X. (2020). Influence of spraying parameters on the microstructure and wear resistance of WC - 12Co coatings deposited by HVOF. Surface & Coatings Technology, 392, 125737.
- Smith, J. (2019). Erosive wear of thermal sprayed WC - Co coatings: A review. Tribology International, 137, 105807.
