Laser cladding

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Abstract
Laser cladding is a hardfacing process that uses a high-powered laser beam to melt the coating material and a thin layer of the substrate to form a pore- and crack-free coating 50 μm–2 mm thick with low dilution that is perfectly bonded to the substrate. The process may be used for large area coverage by overlapping individual tracks, but it is the ability to protect smaller, localized areas that makes it unique. The wide range of materials that can be deposited and its suitability for treating small areas make laser cladding particularly appropriate to tailor surface properties to local service requirements and it opens up a new perspective for surface engineered materials. Laser cladding processes differ in the way the coating material is supplied. In two-step processes a thin layer of material is deposited on the substrate, for example, as a slurry or a thermally sprayed coating, and subsequently melted with the laser beam. In single-step processes the material is fed continuously into the laser generated melt pool, usually in the form of a powder. Laser cladding by powder injection is superior to alternative processes and is the only one that has found practical use, because it is more energy efficient and it allows for better process control and reproducibility. Laser cladding has found relatively widespread use for the protection of materials against wear, corrosion and oxidation, for the deposition of self-lubricating coatings and thermal barriers, and for the refurbishing of high cost industrial components. Other applications with considerable potential are nonequilibrium synthesis of advanced materials, alloy development and free-form near-net shape manufacturing. Some examples of applications are discussed.