26/12/2023
Metal powder materials for 3d printing # 3d printing # alloy powder of 3d printing
Metal 3D printing is a 3D printing technology that uses metal powder to directly print metal parts, also known as metal powder sintering (SLM).
In addition to good plasticity, 3D printing metal powder must also meet the requirements of small particle size, narrow particle size distribution, high sphericity, good fluidity and high loose density.
The metal powders used in most 3D printers today include stainless steel, aluminum alloy, cobalt-chromium alloy, copper alloy, titanium alloy and nickel alloy. Iron base alloy is the most important and the largest amount of metal materials in engineering technology, which is mostly used in the forming of complex structures, and is widely used in aerospace, automobile, ship, machinery manufacturing and other industries.
The type of metal powder and the 3D printing process used determine the performance of the final product
Stainless steel powder
Relatively cheap metal printing materials, cost-effective, good corrosion resistance, high strength, can quickly and efficiently manufacture small batches of complex industrial parts.
Aluminium alloy powder
At present, aluminum alloys applied to metal 3D printing mainly include aluminum-silicon AlSi12 and AlSi10Mg. Alsi 12 is a lightweight additive used in the production of metal powders with good thermal properties. The silicon-magnesium combination gives aluminum alloys higher strength and stiffness, making them suitable for thin walls and complex geometrics-especially in applications with good thermal properties and low weight. Aluminum alloy is the most widely used in the industry of a class of non-ferrous metal structural materials, its low density, high specific strength, close to or more than high-quality steel, good plasticity. Research shows that 3D printing aluminum alloy can achieve dense parts, fine organization, mechanical properties comparable to castings or even better than casting molded parts, and compared with traditional process parts, its quality can be reduced by 22%, but the cost can be reduced by 30%.
Cobalt chromium alloy powder
Metal 3D printed cobalt chromium alloy powder due to its excellent wear and corrosion resistance, commonly used in the printing of various artificial joints and orthopaedic implants, in addition to the dental field are also useful.
Copper alloy powder
Copper, with its excellent thermal and electrical conductivity and excellent thermal conductivity in thermal management applications, can be combined with design freedom to produce complex internal structures and form-following cooling channels.
Titanium alloy powder is widely used in the aerospace field, using the advantages of 3D printing to help optimize product design, such as replacing the original solid body with a complex and reasonable structure, so that the finished product has lower weight and better mechanical properties. This not only reduces costs, but also enables lightweight production of individual components.
Nickel alloy powder
The characteristics of oxidation resistance and corrosion resistance of nickel alloy make it suitable for the harsh environment of high temperature and pressure. When nickel alloy is heated, the alloy surface will passivate a thick and stable oxide layer to protect the internal alloy from corrosion. Nickel alloys maintain good mechanical properties over a wide temperature range.
How Powder materials are used for 3D printing A high-energy laser beam is then controlled by 3D model data to locally melt the metal matrix, while sintering solidifies the powder metal material and automatically stacks it layer upon layer to produce solid parts with dense geometric shapes.
How to produce 3D printed Metal powder Metal powder manufacturing is a fundamental aspect of powder metallurgy. Different methods used to prepare metal powders include reduction, electrolysis, carbonyl decomposition, grinding, and atomization. The four most widely used methods for producing metal powders are solid state reduction, electrolysis, chemical, and atomization. Most manufacturers use electrolysis and reduction methods to produce elemental metal powders. But they are not suitable for making alloy powder. However, atomization tends to overcome this limitation, so manufacturers use it to produce alloy powders. Electrolysis is another method used to produce powdered metals. By choosing the right electrolyte composition, temperature, concentration, and current density, different metals can be deposited as spongy or powdered. This can then be washed, dried, reduced, annealed and crushed. This process produces a very high purity metal powder. Due to its high energy requirements, it is basically used for highly conductive copper powder. Atomization method refers to the method by which the metal melt is mechanically crushed into particles less than 150μm in size. According to the way of crushing metal molten liquid classification, atomization methods include second-flow atomization, centrifugal atomization, ultrasonic atomization, vacuum atomization and so on. These atomization methods have their own characteristics and have been successfully applied in industrial production. The water-gas atomization method has the advantages of simple production equipment and process, low energy consumption and large batch, and has become the main industrial production method of metal powder.
Performance requirements of metal powder for 3D printing
1, the purity of ceramic inclusions will significantly reduce the performance of the final product, and these inclusions generally have a high melting point, difficult to sintering forming, so there must be no ceramic inclusions in the powder. In addition, oxygen and nitrogen content also need to be strictly controlled. At present, powder preparation technology for metal 3D printing is mainly based on atomization method, powder has a large specific surface area, easy oxidation, in aerospace and other special applications, customers have more stringent requirements for this index, such as high temperature alloy powder oxygen content of 0.006%-0.018%, titanium alloy powder oxygen content of 0.007%-0.013%, stainless steel The oxygen content of powder is 0.010%-0.025%.
2, powder fluidity and loose density powder fluidity directly affects the uniformity of the powder laying process and the stability of the powder feeding process. The fluidity is related to powder morphology, particle size distribution and bulk density. The larger the particle size, the more regular the particle shape, and the smaller the proportion of very fine powder in the particle size composition, the better the fluidity. The particle density remains unchanged, the relative density increases, and the powder fluidity increases. In addition, the particle surface absorbs water and gas to reduce the powder fluidity.
3. Powder size distribution Different 3D printing equipment and forming process have different requirements for powder size distribution. At present, the powder particle size range commonly used in metal 3D printing is 15-53μm(fine powder), 53-105μm(coarse powder). The selection of metal powder particle size for 3D printing is mainly divided according to the metal printer of different energy sources, and the printer with laser as the energy source is fine because of its focusing spot, easier to melt fine powder, suitable for the use of 15-53μm powder As a consumable, powder supply method is layer by layer. Electron beam as the energy source of the powder printer, the focus spot is slightly coarse, more suitable for melting coarse powder, suitable for the use of 53-105μm of coarse powder; For coaxial powder delivery printers, powder with particle size of 105-150μm can be used as consumables.
4, powder morphology Powder morphology and powder preparation method is closely related. Generally, when the metal gas or molten liquid is transformed into powder, the shape of the powder particles tends to be spherical, and when the solid state is changed into powder, the powder particles are mostly irregular shape, and the powder prepared by the aqueous solution electrolysis method is mostly dendritic. In general, the higher the sphericity, the better the flow of powder particles.3D printing metal powder requires a sphericity of more than 98%, which makes it easier to lay and feed powder during printing. Importance of 3D metal powder printing Metal powder makes 3D printing faster and allows rapid prototyping. Manufacturers can also modify designs more efficiently. This method is also cost-effective, as metal 3D printers only use the amount of materials needed to manufacture the required parts. It makes it easy to design complex machine parts and enables the production of "impossible" machine parts.
