Nanopowder Effect on Fe Nano/Micro-Bimodal Powder Injection Molding
- PDF / 1,663,548 Bytes
- 11 Pages / 593.972 x 792 pts Page_size
- 73 Downloads / 233 Views
ODUCTION
THE main goal of the manufacturing industry is to produce complex-shaped components with a high production rate and minimal postprocessing. Powder injection molding (PIM) is one of the mass production techniques that satisfy those requirements. PIM uses the shaping advantage of the injection molding technique.[1,2] Binder systems in PIM provide sufficient flowability to be injected for metal or ceramic powders, so the process can produce three-dimensional complex parts, which cannot be easily obtained from traditional powder metallurgy techniques.[3,4] PIM also presents a tight dimensional tolerance. The high design flexibility and tight tolerance make the technique one of the most appropriate manufacturing processes for microfabrication.[5] The PIM process is generally divided into four stages, though some minor steps are often added in the process.[6] First, a powder is mixed with organic binders in a certain ratio to formulate a feedstock. Thereafter,
JOO WON OH and SEONG JIN PARK are with the Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Nam-Gu, Pohang, Gyeongbuk, 37673, Republic of Korea. Contact email: [email protected] WON SIK LEE is with The Advanced Process and Materials R&D Group, Korea Institute of Industrial Technology (KITECH), 156 Gaetbeol-ro, Yeonsu-gu, Incheon, 21999, Republic of Korea. Manuscript submitted December 18, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS A
the feedstock is injected into a mold cavity and formed into a desirable shape. Since carbon and oxygen in the binders will contaminate and degrade the parts during sintering, all the binders are removed from the compacts by debinding. The next stage is sintering. During sintering, the particles bond together by the thermally activated diffusion process and the densification of the samples occurs.[1,7] Nanopowder in the PIM process offers various benefits, e.g., strong adhesion and shape retention, better surface and wear resistance, isotropic shrinkage, and low sintering temperature.[8–12] Furthermore, nanopowder is essential to fabricate microsized features because the average particle size should be less than one-tenth of the minimum feature size.[11,13] However, particle size profoundly influences the process and the particle size effects become prominent as the size approaches nanoscale.[14] Thus, the process condition for nano-PIM cannot be simply converted from conventional micro-PIM. Especially, the large surface area of the powder causes some crucial challenges.[11,15–17] Enhanced particle agglomeration leads to low feedstock homogeneity and defects in samples. High interparticle friction decreases the powder fraction in a feedstock and increases the feedstock viscosity. The most critical issue is the high cost of nanopowder. For these reasons, nanopowder is not widely used in PIM industry despite its numerous advantages. Nano/micro-bimodal powder has been introduced recently to the PIM industry to overcome the limitations of nano-PIM because micropowder, mix
Data Loading...
