Investigation on the hot-deformation behaviour of sintered and forged specimens to improve the forging safety of powder-forged products

Abstract

To improve the forging safety of powder-forged products, the hot-deformation behaviour of sintered and forged alloys was investigated and compared in the present study. The results show that the forged specimen was at a higher risk of cracking than the sintered specimen during the forming process. Furthermore, the finite-element simulation also clearly revealed that both fully dense and not fully dense regions co-existed during the forming process. Therefore, using the processing map of the forged specimen to determine the forging parameters would improve the forging safety of powder-forged products. Finally, a spur gear was manufactured as a model product based on the simulated results.

Finite element simulation of different deformation modes for powder hot forging

“…In the practice of powder metallurgy, the first technological approach uses the scheme of closed volumetric deformation, which provides for additional re-pressing of porous workpieces by upsetting them in a die with a minimum transverse material flow (realised only by filling the technological gap between the wall of the die and the heated workpiece) has found much wider application [1,7,11]. This is largely due to the fact that the use of forging methods, which provide a rapid transition from uniaxial compression to uneven all-round compression, reduces the likelihood of cracks on the side surface of the workpieces, that is especially important for porous materials which have lower ductility compared to compact alloys of similar composition.…”

“…One of the most effective processes of powder metallurgy, providing dense (almost non-porous) workpieces (including complex shapes), is hot forging of porous preforms [1–7]. In addition to the ultimate density that this technology can provide, the materials obtained with its use have other specific features, in particular, hereditary fine grain size, which favourably distinguishes it from the methods of foundry processing or high-temperature liquid phase sintering (in case of using powder metallurgy technology).…”

“…In the practice of powder metallurgy, the first technological approach uses the scheme of closed volumetric deformation, which provides for additional re-pressing of porous workpieces by upsetting them in a die with a minimum transverse material flow (realised only by filling the technological gap between the wall of the die and the heated workpiece) has found much wider application [1,7,11].…”