Additive manufacturing technology is based on the principle of layered manufacturing, the use of materials accumulated layer by layer method, the digital model directly into a solid manufacturing parts of a new manufacturing technology. ASTM International Committee F42 gives the definition of additive manufacturing: Additive Manufacturing is the process of connecting materials to an object based on three-dimensional model data. Compared with subtractive manufacturing, additive manufacturing is usually a layer-by-layer process. Additive manufacturing technology integrates multiple disciplines of digital technology, manufacturing technology, technology and new materials technology, can be directly and quickly manufactured CAD digital model into three-dimensional solid parts, to achieve a true "free manufacturing." Compared with the traditional manufacturing technology, the additive manufacturing technology has a series of advantages such as high flexibility, no mold, short cycle, not limited by the structure of the parts and materials and has been widely used in aerospace, automotive, electronics, medical, military and other fields.
At present, the materials used in laser additive manufacturing technology have covered titanium alloys, superalloys, iron-based alloys, aluminum alloys, refractory alloys, amorphous alloys, ceramics and graded materials. In the field of aerospace, high-performance complex components and organisms Manufacture of porous structures in the manufacturing sector has significant advantages. Laser additive manufacturing technology is classified according to its forming principle. The most typical are selective melting (SLM) and powder metallurgy (LMDF) with synchronous powder delivery.
Laser direct metal forming (LMDF) technology is the use of rapid prototyping the basic principles of the metal powder as raw material, the use of high-energy laser as the energy source, according to the predetermined processing path, the metal powder sent simultaneously to layer by layer melting, Rapid solidification and layer by layer deposition, in order to achieve the direct manufacture of metal parts. Typically, the laser metal direct forming system platform includes: laser, CNC CNC table, coaxial powder feeding nozzle, high-precision adjustable feeder and other auxiliary devices. Laser metal direct forming technology integrates the advantages of laser cladding and rapid prototyping technology with the following features:
No molds are needed to make complex structures, but cantilever structures require the addition of corresponding support structures. Molding size is unlimited, enabling the manufacture of large-size parts. Can be achieved by mixing different materials and manufacturing gradient materials. Quick repair of damaged parts. Forming uniform, with good mechanical properties, enabling the manufacture of directional tissue.
Economical and efficient equipment is the basis for the extensive promotion and development of additive manufacturing technology. With the current use of high-power lasers and the continuous improvement of the powder feeding efficiency, the processing efficiency of laser additive manufacturing has been significantly improved. However, The manufacturing efficiency of size parts is still low, and the price of laser additive manufacturing equipment is too high. Therefore, it is of great significance to further improve the processing efficiency of equipment and reduce the cost of equipment.
For metal materials, laser additive manufacturing technology, the metal powder is the raw material, the quality of metal powder will directly affect the final quality of the formed parts. However, there is no metal powder specially made for laser additive manufacturing. Nowadays, the metal powder used in the laser additive manufacturing process has been developed by the thermal spraying process such as plasma spraying, vacuum plasma spraying and high-speed oxygen fuel flame spraying, Basically use the atomization process. Such metal powder in the production process may form some hollow particles, the hollow particles of metal powder used in additive manufacturing, will lead to holes in the parts, cracks and other defects.