PVD Coating for Stainless Steel Tubes

PVD coating

Let’s discuss PVD coating, this article can help you to get informed about PVD coating.

  1. PVD is the abbreviation for “Physical Vapor Deposition”, and refers to a technology of thin film preparation that uses physical methods to deposit materials on a plated workpiece under vacuum conditions. PVD (physical vapor deposition) technology is mainly divided into three categories, that are vacuum evaporation coating, vacuum sputter coating and vacuum ion coating. Relative to the three categories of PVD technology, the corresponding vacuum coating equipment is referred to as vacuum evaporation coating machine, vacuum sputter coating machine and vacuum ion coating machine. The development of vacuum ion plating technology has been the fastest in the last decade, and has become one of the most advanced surface treatment methods in the contemporary. What we usually refer to as “PVD coating” is actually vacuum ion coating, and the machines that are commonly called “PVD coating machines” refer to vacuum ion coating machines.

 

  1. What is the specific principle of PVD coating?
    The principle of Vacuum Ion Coating (PVD coating) technology is to use a high current arc discharge at a high voltage under vacuum conditions, which produces a gas discharge that evaporates the coating material and ionizes it. Then, under the action of the electric field, the evaporated and ionized substance (or its reaction product) is deposited on the workpiece.

 

  1. What are the advantages of PVD coatings as compared to traditional chemical plating?
    PVD coatings are similar to traditional chemical plating in that both of them belong to the category of surface treatment, and cover a material’s surface with another in a certain way. However, PVD coating differs from the other in certain ways, such that the binding force between the PVD coating film and the surface of the workpiece is greater, the film layer is harder and has a lower friction coefficient. Moreover, it has excellent ductility and uniformity in coating and has a better contact-resistance, wear-resistance and corrosion-resistance as compared to traditional chemical plating. It also has a more stable film and a better performance. Further, a large variety of coatings with various beautiful colors can be used for PVD coatings.
    Also, the PVD coatings do not produce toxic or polluting substances.

 

  1. Features of PVD coating technology
    PVD coating technology is an environment-friendly surface treatment method that can truly obtain micron-level coatings without any pollution. It can prepare various single metal films (such as aluminum, titanium, zirconium, chromium, etc.), nitride films (such as TiN, ZrN [zirconium gold], CrN, TiAlN, etc.), carbide films (TiC, TiCN), and oxide films (such as TiO, etc.). The resultant ceramic coating is so thin that the texture of the underlying surface is still visible. These PVD color-coatings do not fade over time and have the advantage of being more uniform and abrasion-resistant than the coloration done by electrochemical methods. The film layer deposited by PVD coating technology has the characteristics of high hardness, high wear resistance (low friction coefficient), good corrosion resistance and chemical stability and a longer life. Meanwhile, the film layer can also greatly improve the appearance of the workpiece and decorate it.

 

  1. The process of PVD coating
    PVD vacuum coating can be directly plated on stainless steel, titanium, tungsten steel and other materials. Products made from stainless steel are brighter and have a strong metallic feel. In this process, the stainless-steel surface is first cleaned to ensure that the coating adheres properly. The steel is then placed in a vacuum chamber with the “target” metal that is to be used to create the coating. A high vacuum is produced in the coating chamber, and then a small amount of argon is introduced. In order to ensure the adherence of the target metal to the stainless steel, a high voltage current is used. This allows argon ions to bombard the target and release atoms of the target metal, which are deposited as a coating on a stainless-steel substrate.

This PVD process, known as “sputtering”, causes plasma to be deposited on the stainless-steel surface, giving it a new strength and gloss. The cleaning process before vacuum coating is very important because it directly affects the quality of coated products. Before the product enters the vacuum coating chamber, it must be carefully cleaned. Surface contaminations come from various sources such as dust, lubricants, engine oils, polishing waxes, grease, sweat stains, etc. and adhere to the workpiece during processing, transportation or packaging. To avoid processing defects, they should be removed by degreasing or chemical cleaning methods. The products with cleaned surfaces should not be stored in the atmosphere. They should be placed in closed containers or clean cabinets to reduce contamination by dust. Glass substrates can be stored in steel-oxidized aluminum containers to absorb nitrogen oxide vapor. However, because these containers preferentially adsorb carbon oxides, they should be minimized. Vacuum-coating substrates with highly unstable water-vapor sensitive surfaces should usually be stored in a vacuum oven. Keeping the room clean is a basic requirement for the coating process, thus it is necessary to remove dust in the coating chamber and set up a room with high cleanliness before the vacuum coating process. In areas with higher humidity, the substrate and vacuum chamber must be carefully cleaned, followed by baking and degassing in addition to the application of coating film.

 

  1. Abrasion and weather-resistance
    The thickness of the PVD coating film is relatively thin (few microns), generally 0.1 μm to 5 μm. Meanwhile, the thickness of the decorative coating film layer is generally 0.1 μm to 1 μm, so the workpiece surface can be improved without affecting the original size of the workpiece. Various physical and chemical properties of the workpiece remain unchanged, the original size is unaffected and no further processing is required after plating.
    The PVD process not only increases the life of the product but also reduces maintenance requirements without changing its original texture and structure. Also, it has been used for products that require wear and weather resistance. Further, PVD has a longer service life than other coatings of similar thickness.

 

  1. PVD coating cost is not high
    Although the PVD coating technology can be used to deposit high-quality coatings, the cost of this process is not very high. It is a very cost-effective surface treatment method that produces a product with a bright mirror-like surface, uniform color with long-lasting color retention, and appropriate hardness, wear resistance and good deformation properties. This is why PVD coating technology has developed swiftly in the recent years and has become the direction of development of surface treatment in the hardware industry.

 

  1. PVD is environment-friendly
    The PVD process is also more environment-friendly than alternative methods such as electroplating and spray painting, and can produce a surface effect that has a good gloss that cannot be achieved with ordinary electroplating.
    It is important to note that the coloring process does not limit the recycling value of stainless steel. In the industry of surface treatment, vacuum plating has become a new trend because of its environment protection. Since all coating materials are deposited on the surface of the workpiece through plasma in a vacuum electroplating environment, it is safer, more energy efficient and reduces noise and emissions. No pollutant solution is formed, and the process does not release any gas, waste water or any other residue. In conclusion, the environmental damage is reasonably small.

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