3D printing metal materials are mainly in the form of powder and wire. Powder materials are the most commonly used materials, which can be used in a variety of 3D printing processes such as Selective Laser Melting (SLM), Laser Engineered Net Shaping (LENS), and Electron Beam Melting (EBM); Wire material is suitable for wire and Arc Additive Manufacture (WAAM) and other processes.
In order to meet the process requirements of 3D printing, metal powder must meet certain requirements. The fluidity of powder is one of the important characteristics of powder. All 3D printing processes using metal powder as consumables involve the flow of powder in the manufacturing process. The fluidity of metal powder directly affects the uniformity of powder spreading in SLM and EBM and the stability of powder feeding in LENS. If the fluidity is too poor, the printing accuracy will be reduced or even the printing will fail. The fluidity of the powder is affected by the particle size, particle size distribution, powder shape, water absorbed and other aspects. In order to ensure the fluidity of the powder, it is generally required that the powder is spherical or nearly spherical, and the particle size is between ten microns and one hundred microns. Too small particle size is easy to cause agglomeration of the powder, while too large particle size will lead to reduction of printing accuracy. In addition, in order to obtain more compact parts, it is generally hoped that the higher the loose specific gravity of the powder is, the better. It is easier to obtain higher loose specific gravity by using graded powder than by using powder with a single particle size distribution. At present, the preparation method of metal powder used in 3D printing is mainly atomization method. The atomization method mainly includes water atomization method and gas atomization method. Compared with water atomized powder, the powder prepared by gas atomization has high purity, low oxygen content, controllable particle size, low production cost and high sphericity, which is the main development direction of high-performance and special alloy powder preparation technology.
The metal wire used for 3D printing is the same as the traditional welding wire. In theory, any metal that can be melted under the process conditions can be used as the material for 3D printing. The silk material manufacturing process is very mature, and the material cost is much lower than that of powder material.
According to the types of materials, 3D printing metal materials can be divided into iron based alloys, titanium and titanium based alloys, nickel based alloys, cobalt chromium alloys, aluminum alloys, copper alloys and precious metals.
Iron base alloy is a kind of alloy that has been studied earlier and more deeply in 3D printing metal materials. The commonly used iron base alloys include tool steel, 316L stainless steel, M2 high-speed steel, H13 die steel and 15-5PH maraging steel. Iron base alloy has low cost, high hardness, good toughness and good machinability, which is particularly suitable for mold manufacturing.
Nickel base alloy is one of the fastest growing and most widely used superalloys. It has high strength and certain corrosion resistance at 650~1000 ° C, and is widely used in aerospace, petrochemical, shipbuilding, energy and other fields.
Cobalt based alloys can also be used as superalloys, but their development is limited due to lack of resources. Cobalt based alloys have better biocompatibility than titanium alloys. At present, they are mostly used as medical materials for the manufacture of dental implants and orthopedic implants.
Aluminum alloy is an ideal lightweight material with low specific gravity, good corrosion resistance, high fatigue resistance, and high specific strength and stiffness.