Piocreat:3D printing is changing the world-revealing the influence of the shape, size and distribution of metal powder particles on 3D printed products
What is 3D printing?3D printing (3 Dimensional Printing), also known as material additive manufacturing, is a process that enables three-dimensional solid objects of any shape to be quickly realized through digital models. The essence of 3D printing is to use computer-aided design software to perform a series of digital slice editing of a certain processing pattern to generate a digital model file, and then use certain specific additives as the bonding material according to the size of the model drawing. , Using a specific molding equipment, namely a
3D printer, to use solid metal powders such as powder, liquid, and filaments or materials with high plasticity for layered processing and superimposed molding to make the raw materials melt and increase these thin layers layer by layer, so as to finally "print "A real and three-dimensional solid object. Popularity is similar to squeezing toothpaste, except that the squeezed out toothpaste is stacked into a specific shape and structure according to certain procedures. 3D printing technology is known as "manufacturing technology with industrial revolution significance". It is an emerging technology that is rapidly developing in the manufacturing industry. It has become an effective means of manufacturing modern models, molds and parts. Materials science and other fields have been applied to some extent.
Metal powder for 3D printing Metal parts 3D printing technology, as the most cutting-edge and most potential technology in the entire 3D printing system, is an important development direction of advanced manufacturing technology. Metal powder for 3D printing is the most important part of the 3D printing industry chain for metal parts, and it is also where the greatest value lies. The metal powder for 3D printing will be introduced in detail below.
At the "2013 World Conference on 3D Printing Technology Industry", authoritative experts in the world's 3D printing industry gave a clear definition of metal powder for 3D printing, that is, a group of metal particles smaller than 1mm in size. Including single metal powder, alloy powder and some refractory compound powder with metallic properties. At present, metal powder materials for 3D printing include cobalt-chromium alloys, bronze alloys, industrial steel, stainless steel, titanium alloys, and nickel-aluminum alloys. However, in addition to good plasticity, metal powders for 3D printing must also meet the requirements of fine powder particle size, narrow particle size distribution, high sphericity, good fluidity and high bulk density. The following is a detailed introduction to the influence of the shape, size and distribution of metal powder particles on the quality of 3D printing products.
The influence of metal powder particle shape, size and distribution on 3D printed products
Particle shape: In the metal powder preparation process, the powder particles will take on different shapes depending on the preparation method, such as spherical, nearly spherical, polygonal, porous sponge, dendritic, etc. The particle shape of the powder directly affects the fluidity and bulk density of the powder, which in turn affects the performance of the prepared metal parts.
Generally speaking, spherical or near-spherical powder has good fluidity, it is not easy to block the powder supply system during the printing process, and can be spread into a thin layer, thereby improving the dimensional accuracy and surface quality of 3D printed parts, as well as the density and organization of the parts. Sex is the preferred material shape type for 3D printing. However, it should be noted that the particle packing density of the spherical powder is small, and the gap is large, which makes the parts less dense and also affects the forming quality.
The development of metal powder preparation technology for 3D printing restricts the development of the 3D printing metal parts industry. The breakthrough of low-cost preparation technology of metal powder for 3D printing has become an urgent problem for researchers at home and abroad to overcome. In recent years, domestic and foreign enterprises have invested a lot of capital and technical strength in the field of 3D printing metal powder preparation, and have made certain progress. The following are two kinds of metal powders. Using Feiner desktop scanning electron microscope to compare the micro morphology of the two powders, it can be seen that metal powder A is better than metal powder B. Metal powder A is basically full of spherical particles, almost not glued together. The metal powder B has various shapes, such as spherical, rod-shaped and irregular shapes.
Powder size and distribution:The smaller the particle size of the metal powder, the more conducive to the smooth progress of sintering, because the smaller the particle size, the greater the specific surface area, and the greater the driving force for sintering. In addition, the gaps between the fine powder particles are small, and the adjacent powder layers are tightly connected, which is beneficial to improve the sintering densification and sintering strength. Small particles of metal powder can also be filled into the gaps of large particles, which can increase the bulk density of the powder, thereby helping to improve the surface quality and strength of the printed metal parts. However, it is not that the finer the particles are, the better. If there are too many fine particles, the phenomenon of "spheroidization" is likely to occur during the sintering process, and the thickness of the spreading powder is likely to be uneven. The so-called "spheroidization" phenomenon is a phenomenon in which the surface of the molten metal and the surface of the surrounding medium have the minimum free energy. Under the action of surface tension, the shape of the molten metal surface changes to a spherical surface. "Spheroidization" usually makes the metal powder unable to solidify after melting to form a continuous and smooth molten pool, so the formed parts are loose and porous, resulting in molding failure.
The particle size of the metal powder used for 3D printing is also different depending on the heat source. Generally speaking, the particle size of the powder formed by laser is 30-50 μm, and the particle size of the powder formed by electron beam is 50-90 μm. When the large particles and small particles of the metal powder are mixed in an appropriate ratio, high-quality 3D printed metal products can be obtained.