The metal powder used for 3D printing generally requires high purity, good sphericity, narrow particle size distribution, and low oxygen content. At present, water atomized pure iron powder is mainly used in 3D printing for metal powder materials such as titanium alloys, cobalt chromium alloys, stainless steels, and aluminum alloy materials. In addition, there are precious metal powder materials such as gold and silver for jewelry printing. 3D printing metal powder, as the most important part of the 3D printing industry chain for metal parts, is also of great value.

At the "2013 World 3D Printing Technology Industry Conference", authoritative experts in the world's 3D printing industry gave a clear definition of 3D printed metal powder, which refers to a group of metal particles smaller than 1mm in size. These include single metal powders, alloy powders, and certain refractory compound powders with metallic properties. Currently, 3D printed metal powder materials include cobalt chromium alloys, stainless steels, industrial steels, bronze alloys, titanium alloys, and nickel aluminum alloys. However, in addition to good plasticity, 3D printed metal powder must also meet the requirements of fine powder particle size, narrow particle size distribution, high sphericity, good fluidity, and high bulk density.

Titanium alloy

Titanium alloy has the advantages of high temperature resistance, high corrosion resistance, high strength, low density, and biocompatibility. It has been widely used in aerospace, chemical, nuclear industry, sports equipment and medical equipment. Titanium alloy parts prepared by traditional forging and casting techniques have been widely used in high-tech fields, and a Boeing 747 aircraft uses 42.7t of titanium. However, the traditional forging and casting methods for producing large titanium alloy parts have hindered their wider application due to unfavorable factors such as high product costs, complicated processes, low material utilization, and difficult subsequent processing. And metal 3D printing technology can fundamentally solve these problems, so this technology has become a new technology for direct manufacturing of titanium alloy parts in recent years. The development of new titanium-based alloys is the main research direction of titanium alloy SLM applications. Due to the low strain hardening index of titanium and titanium alloys (approximately 0.15), the ability to resist plastic shear deformation and wear resistance is poor, thus limiting the use of its parts under high temperature and corrosion and wear conditions.

However, the melting point of rhenium (Re) is very high, and it is generally used in ultra-high temperature and strong thermal shock working environments. , The working temperature can reach 2200 ℃. Therefore, the preparation of Re-TI alloys has great significance in the fields of aerospace, nuclear energy and electronics. Ni has magnetic properties and good plasticity, so Ni-TI alloy is a commonly used shape memory alloy. The alloy has properties such as pseudo-elasticity, high elastic modulus, damping characteristics, biocompatibility and corrosion resistance. In addition, research on titanium-alloy porous structure artificial bone is increasing. Kyoto University of Japan has made different artificial bones for 4 patients with cervical disc herniation through 3D printing technology and successfully transplanted them. The artificial bone is Ni-TI alloy.

stainless steel

Stainless steel has the characteristics of chemical resistance, high temperature resistance and good mechanical properties. It is the earliest material used for 3D metal printing due to its good powder moldability, simple preparation process and low cost. For example, Huazhong University of Science and Technology, Nanjing University of Aeronautics and Astronautics, and Northeastern University have conducted in-depth research on metal 3D printing. The current research focuses on reducing the porosity, increasing the strength, and the spheroidizing mechanism of the metal powder during the melting process. Li Ruidi and others used different process parameters to carry out SLM forming tests on 304L stainless steel powder, obtained the empirical formula for the density of 304L stainless steel, and summarized the grain growth mechanism.

According to the analysis and discussion of the spheroidization mechanism and the factors affecting spheroidization during the forming process of 316L stainless steel, it is considered that when the laser power and the thickness of the powder layer are constant, an appropriate increase in scanning speed can reduce the spheroidization phenomenon. When the thickness is fixed, as the laser power increases, the spheroidization phenomenon increases. Ma et al. Conducted laser melting of 1Cr18Ni9Ti stainless steel powder and found that when the thickness of the powder layer increased from 60 μm to 150 μm, the dendrite spacing increased from 0.5 μm to 1.5 μm, and finally stabilized at about 2.0 μm. The hardness of the sample depends on the direction of the melting region. Anisotropic microstructure and grain size. Jiang Wei uses a series of stainless steel powders to study the influence of powder characteristics and process parameters on the quality of SLM forming. The results show that the mechanism of the special properties of powder materials and process parameters on SLM forming is mainly in the selective laser forming process. The influence of the quality of the molten pool, the process parameters (laser power, scanning speed) mainly affect the depth and width of the molten pool, so as to determine the quality of the SLM formed parts.

Superalloy

High-temperature alloy refers to a class of metal materials based on iron, nickel, and cobalt that can work for a long time under a high temperature of 600 ° C and a certain stress environment. It has high high temperature strength, good resistance to hot corrosion and oxidation, and good plasticity and toughness. At present, according to the types of alloy substrates, it can be roughly divided into three types: iron-based, nickel-based and cobalt-based alloys. High-temperature alloys are mainly used in high-performance engines. In modern advanced aircraft engines, the amount of high-temperature alloy materials used accounts for 40% to 60% of the total mass of the engine. The development of modern high-performance aero-engines has increasingly demanded the use temperature and performance of superalloys. The traditional ingot metallurgy process has a slow cooling rate, some elements in the ingot and the second phase are severely segregated, the hot workability is poor, the structure is uneven, and the performance is unstable. And 3D printing technology has become a new method to solve technical bottlenecks in high temperature alloy forming. NASA claims that in a high-temperature ignition test conducted on August 22, 2014, a rocket engine nozzle manufactured through 3D printing technology produced a record 9t thrust.

magnesium alloy

As the lightest structural alloy, magnesium alloy has the possibility of replacing steel and aluminum alloy in many applications due to its special high strength and damping properties. For example, the lightweight application of magnesium alloys in automotive and aircraft components can reduce fuel consumption and exhaust emissions. Magnesium alloy has in-situ degradability, low Young's modulus, strength close to human bone, excellent biocompatibility, and has more application prospects than traditional alloys in surgical implantation.

The in-depth application of 3D printing technology in industrial fields, biomedical fields, cultural and creative fields, and promotes 3D printing and aerospace, military industry, automotive and parts, industrial design, cultural creativity, innovative education, orthopedics, and other major surgery, rehabilitation, Combination of traditional techniques such as cultural relic restoration.