Metals can be processed through machining (material removal), forging (heat), bending (mechanical force), and layer-by-layer building up (additive manufacturing). Laser has been used in two common additive metal manufacturing processes: Laser Metal Deposition (LMD), and Laser Metal Fusion (LMF) or 3D printing.
In LMD, a laser beam generates a melt pool on the surface of the component (substrate) before a stream of metal powder is blown into that melt pool and fused to the substrate. These layers are highly precise, both in overlap and size. Since the added material only minimally dilutes the substrate, in many applications a single layer is all that is needed for undiluted material at the surface. The metallurgical bond created is significantly stronger than other coating or cladding methods and it is typically applied to protect the part against corrosion or wear, such as along the edge of cutting blades for high wear resistance. Turbine blade and shaft repairs, as well as commercial diesel engine parts (pistons, heads) are also ideal applications.
LMF is most commonly referred to as metal 3D printing. To begin, software is used to slice a 3D model into very thin layers, usually 20 microns to 100 microns thick. Each slice is then optimized for fusion quality, part density and heat management throughout the build. Using a powder-bed based laser fusion process, the part is ultimately built up layer by layer. A layer of metal powder is applied to a substrate plate and then a laser beam, directed through a scanner optic, fuses the cross section of the geometry to the plate. After the exposure the plate is lowered and the next layer of powder is applied. The process repeats until the part is finished. LMF provides for very fine or highly complex 3D structures to be built, including internal structures and surface features.