Common problems with 3D printed tungsten products
Compared with traditional powder metallurgy method, 3D printing (add material manufacturing), although there is a lower production cost, shorter production cycle, production is more efficient and can produce more complex alloy structure etc advantages, but printed tungsten products is likely to remain the following several problems, including porosity, residual stress, density, warp, crack and surface finish, etc.
3D-printed tungsten products can have pores, and these pores can reduce the overall density of the product, leading to cracking and fatigue problems. The reasons for the formation of pores are as follows: first, the 3D printing process itself will produce holes, especially when the laser power is too low, resulting in incomplete melting of metal powder; Two is the spherical tungsten powder; Third, the laser lap is too sparse, resulting in holes.
2. Residual stress
When the residual stress exceeds the tensile strength of tungsten material, tungsten parts will have defects, such as cracks. Residual stresses are concentrated at the joints between the parts and the substrate. In additive manufacturing, residual stress is caused by cold and heat change, expansion and contraction process.
The density of a tungsten part is inversely proportional to the amount of porosity, which means that the more pores there are, the lower the density and the poorer the fatigue resistance of the part. The reason of density decrease is not only related to printing technology, but also related to the basic properties of tungsten powder, such as particle shape, particle size and particle size distribution. In general, spherical, small and narrow particle size distribution is more conducive to the manufacture of high density tungsten products.
The crack formation of tungsten parts is not only related to the porosity and density of tungsten parts, but also affected by improper operation. When the heat source power is too large, the cooling process is likely to produce stress, leading to cracks in parts. In addition, the occurrence of delamination may lead to interlayer fracture.
5. Surface finish
The tungsten parts produced by powder bed melting method are closer to the shape required by customers, but the surface of the products is relatively rough. The parts produced using the direct energy deposition method are also close to the shape the customer wants, but it must undergo CNC processing. Note: Powder bed melting and direct energy deposition are two common methods of 3D printing.