Spray compacting

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Spray compacting is a manufacturing process from the group of primary forming processes . To produce near-net-shape components or semi-finished products (blocks, bolts, discs, sheets, pipes), a molten metal is sprayed through a nozzle. The spray jet is directed at a substrate or a collecting surface, where the liquid or solidifying melt droplets are "compacted" into a solid body. If you set the collecting surface in a slow rotation and gradually pull it downwards, then a bolt-shaped body "grows" up in return.

origin

One of the pioneers of spray compaction is Professor Singer, who was looking for new ways to shape steel at the University of Swansea in Wales in the 1970s . Starting from the spraying of metallic melts, which was already known from powder metallurgy, the sprayed melt droplets were not allowed to solidify into metal powder, but rather the spray jet was "compacted" directly into the desired solid body. The detour of powder metallurgy, namely pressing the powder into a mold and sintering , is thus avoided.

advantages

The advantages of spray compacting arise from the high cooling rate. At 1000 to 10000 K / s, this is only slightly below the cooling rates of powder metallurgy, but several orders of magnitude above the cooling rates of classic casting processes. This considerably expands the possibilities of metallurgy compared to casting processes. Spray compacting enables alloys to be produced that could not be produced using foundry technology or metal forming technology. Spray-compacted steels have a particularly homogeneous material structure, segregation can largely be avoided. Special structural components that are required to achieve special material properties, such as B. Manganese sulfides or carbides, can be produced much finer-grained with spray compacting than with the casting technique. As a result, strength and toughness are improved. Even with aluminum and magnesium alloys, spray compacting can be used to produce particularly high-performance alloys with high strength and temperature resistance.

disadvantage

One disadvantage of spray compacting is the spray losses (overspray). As in painting technology, it is inevitable that a certain proportion of the spray jet will miss its target. Another potential disadvantage is that a 100% pore-free material cannot normally be produced using spray compacting.

variants

  • The melt can be atomized by a gas jet or by centrifugal forces.
  • A gas nozzle can be operated with an inert gas or with a reaction gas.
  • In addition to the melt spray jet, solid particles can be fed in with a powder jet.
  • Several jets of melt spray can be used at the same time.
  • The substrate can be moved linearly and rotationally in a variety of ways.