Application of Thermal Spray Deposition Process on Rollers
Rollers are vital components in many industrial processes. Their performance is critical to the efficient functioning of the entire system and their long-term reliability is accordingly important. But some problems such as wear, corrosion, and fatigue may occur with various rollers in industrial distributed applications, which can drastically reduce their performance and ultimately cause unscheduled maintenance and/or equipment downtime. To address these issues and enhance the properties of rollers, many coating technologies have been developed and researched. Among these technologies, thermal spray deposition has shown some unique advantages.
Thermal spray deposition is a surface engineering technology, which can use a variety of materials to build up layers upon a substrate. It is an ideal process for fabricating protective coatings with favorable adhesion, hardness, wear and corrosion resistance, and fatigue life. Thermal spray deposition is capable of producing thick, porous protection layers and can assure a good bonding between the substrate and coating, as long as the optimum processing conditions are appropriately established. Furthermore, it is a cost-effective process with high efficiency, which can be applied in various working environments, such as hostile and extreme environments.
Rollers usually comprise a base layer and several accessory layers, among which the base layer is setup to primarily safeguard against abrasion and corrosion. Besides, the base layer should be compliant to various conditions and has to meet the requirements of the entire systems. Generally, the selection of roller material should consider properties such as wear performance, coefficient of friction, temperature, and corrodes of fluids used in the process. For example, stainless steel is often utilized at room temperature due to its excellent corrosion resistance, but would suffer from low wear resistance; whereas metals such as chromium plating or hard coating can be chosen to enhance wear resistance.
In many applications, thermal spray deposition is employed for the coating of rollers. In this technique, the thermal spray parameters, processing method, and building materials used should be cautiously evaluated and selected according to the rollers material properties, the abrasive and corrosive environment of the roller, and its required lifetime. Most commonly, thermal spray deposition is performed by using a wire or powder as the deposition material. Spray wires are generally predominantly made of chromium, nickel, aluminum, or stainless steel. While, spray powders can potentially be selected from a much wider range of materials such as ceramics, metals, or organometallic materials. Many of these materials have excellent corrosion, abrasion, and wear resistance, for instance: zinc is used for its excellent electrochemical behavior in seawater and oil; chromium offers extraordinary wear resistance; and aluminum provides excellent electrical insulation.
The erosion and wear of rollers can also be effectively reduced by means of laser cladding deposition and electron beam technology. Laser cladding is capable of rapidly producing high-melting-point, oxidation and corrosion-resistant coatings. It is usually performed in gas atmosphere and utilizes a laser beam and materials deposited in powder or strip form on the surface of the substrate. Its main distinctive advantage is its precision and ability to coat complex geometries. Whilst electron beam deposition is a process where a beam of electrons is directed by a cross-field coil system and utilized to melt a consumable wire or powder to form a coating on substrate. Electron beam deposition is capable of producing coatings of exceptional properties, such as high strength and excellent wear, corrosion and heat resistance.
In conclusion, thermal spray deposition is one of the most frequently used techniques for rollers improvement. This deposition process has numerous advantages, such as good bonding, high efficiency, and low cost. Furthermore, more recent advanced techniques such as laser cladding and electron beam deposition can further advance the properties of rollers, such as wear and corrosion resistance.
