Chemical Vapour Deposition (CVD) has emerged as a highly effective method for coating components that face extreme conditions and environments. By depositing material atom-by-atom in a controlled environment, CVD produces coatings that are exceptionally durable, uniform and versatile. This article walks through the CVD process step by step, highlights its key benefits, and explores why it is the method of choice for coating complex metal components.
Upon receipt of parts, a detailed inspection is carried out to verify that the components conform to the customer's specifications and provided drawings. This ensures that all parts are accurately identified, free from damage and ready for processing. Depending on customer requirements, the inspection process can include full CMM measurement.
Before the coating process begins, the component is cleaned to remove contaminants such as oil, grease or oxides. This ensures the surface of the component is as clean as possible to ensure proper adhesion of the coating.
Once the part has been cleaned, it undergoes a series of pretreatment processes depending on the substrate material. This may include electroless nickel plating or nickel plating to optimise the surface for the CVD phase of the overall coating process.
The chamber is sealed, and the air is evacuated to create a vacuum or low-pressure environment. The component is heated to a specific temperature, typically around 1000°C, for traditional CVD and around 500°C for Hardide’s bespoke CVD process. This temperature is critical for enabling the chemical reactions necessary for the coating to form.
A carefully controlled mixture of reactive gases is introduced into the chamber. These gases contain the elements required for the coating, such as tungsten or tungsten carbide. The temperature and pressure conditions cause these gases to decompose or react chemically.
The gas-phase reactions result in the formation of a solid material, which crystallises atom-by-atom onto the surface of the component. This deposition is incredibly uniform, even on internal surfaces or complex geometries, creating a dense, pore-free coating.
The CVD process allows precise control over coating thickness, ranging from 10 to 100 μm with typical thicknesses being 35 to 50 μm, though it can be tailored further for specific applications. This ensures components are optimally protected without compromising dimensional accuracy.
Once the desired coating thickness is achieved, the reactor is cooled, and the component is removed. Minimal post-processing is required due to the smooth and conformal nature of the coating, though sometimes polishing is desired for specific applications where the surface roughness of less than 0.5 μm Ra is achievable.
After cooling, a thorough inspection is performed in the laboratory. Witness samples included in the batch undergo destructive testing to confirm coating thickness, hardness and other quality parameters. Technical reports are prepared based on these findings, ensuring compliance with customer requirements and load specifications.
CVD excels at coating intricate geometries, including blind holes, internal surfaces and sharp edges. Unlike traditional line-of-sight methods like HVOF, which struggle to coat hidden areas, CVD ensures every surface receives consistent protection.
CVD coatings are entirely pore-free, providing an excellent barrier against corrosion and chemical attack. This is especially advantageous in industries like oil and gas, where components are exposed to aggressive environments.
CVD coatings combine high hardness (up to 1600 Hv) with superior toughness. This makes them resistant to wear, erosion and impact, significantly extending the operational life of components in demanding applications.
The smooth and uniform deposition reduces the need for grinding or finishing. This saves time and costs, especially for components with tight tolerances.
The CVD process represents a leap forward in coating technology, offering unparalleled uniformity, durability and environmental compliance. By addressing the limitations of traditional methods, CVD is becoming the preferred choice for protecting components in aerospace, energy, manufacturing and beyond. Its ability to extend component life, reduce maintenance, and enhance performance makes it an invaluable tool for engineers striving for excellence in today’s competitive industries.
To find out more about Hardide's innovative CVD process and how it excels in sustainability as well as component durability, read our comprehensive guide below.