Production of Rounded Reactive Composite Ti/Al Powders for Selective Laser Melting by High-Energy Ball Milling
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itive manufacturing (AM) is an efficient tool to produce complex-shaped,[1] functionally-graded[2] or non-standard machine parts[3] for various engineering applications. Currently, AM is used not only in rapid printing of prototypes but also in production of real-scale functional parts. For example, selective laser sintering (SLS) was initially developed for production of polymer prototypes by using the point-by-point scanning technique. Afterward, due to the use of more potent heat sources, this approach was also extended to metallic and ceramic powders. Porous parts fabricated by SLS are now widely employed in biomedicine.[4–6] Since the process of selective laser sintering (SLS) or melting (SLM) involves the operation of layer-by-layer deposition, the physical and technological properties of used powders become of pivotal importance. During preliminary formation of powder layer (usually 20 to 100 lm thick), it is necessary to ensure homogeneous
A.A. NEPAPUSHEV, D.O. MOSKOVSKIKH, and V.S. BUINEVICH are with the Center of Functional Nanoceramics, National University of Science and Technology MISiS, Leninsky pr. 4, Moscow, Russia, 119049. Contact e-mail: [email protected] V.S. VADCHENKO and A.S. ROGACHEV are with the Merzhanov Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, Chernogolovka, Moscow, Russia, 142432. Manuscript submitted 12 April, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS B
distribution of powder particles over the entire surface. In case of fine powders, the deposited layers are thinner, which ensures higher precision and better properties of resultant product. However, a decrease in particle size leads to an increase in interparticle friction and electrostatic forces, which decreases the flow ability of powder and elevates inflammability hazard. In order to prepare thin, smooth, and reproducible layers, the shape of powder particles should be highly symmetrical since such particles can be distributed more uniformly and packed more closely. The shape and size of powder particles are known to strongly depend on a method of their production. Currently, most popular are the methods of melt atomization by a gas or water jet[7,8] and plasma rotating electrode process.[9–11] Water-atomized powders often have irregular shape since high cooling rates suppress the action surface tension forces during droplet spheroidization. Application of inert gas instead of water allows one not only to make powders more spherical but also to widen the nomenclature of produced powders. However, both methods exhibit a common drawback: the formation of agglomerates (satellite particles) with a wide size distribution. Alternatively, the plasma rotating electrode process can be employed to produce high-purity spherical powders. However, low productivity of this method and high production cost restrict its implementation.
Currently, pure metals are rarely used in AM technologies in view of their low mechanical properties and oxidation/corrosion resistance. The use of pre-alloyed Ti,
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