The objective of this study is to examine the feasibility of manufacturing WC-Co milling insert by PIM process. WC-Co is used in a wide variety of cutting tools due to its high hardness, stiffness, compressive strength and wear resistance properties. WC-Co parts for a high stress application were conventionally produced by the press and sinter method, which were limited to 2 dimensional shapes. Manufacturing WC-Co parts for a high stress application by PIM implies that tool efficiency can be highly improved due to increased freedom in design.
This study investigated the microstructure and high temperature oxidation properties of Fe-25Cr-20Ni-1.5Nb, HK30 alloy manufactured by metal injection molding (MIM) process. The powder used in MIM had a bi-modal size distribution of 0.11 and 9.19 μm and had a spherical shape. The initial powder consisted of γ-Fe and Cr 23 C 6 phases. Microstructural observation of the manufactured (MIMed) HK30 alloy confirmed Cr 23 C 6 along the grain boundary of the γ-Fe matrix, and NbC was distributed evenly on the grain boundary and in the grain. After a 24-hour high temperature oxidation test at air atmospheres of 1000, 1100 and 1200°C, the oxidation weight measured 0.72, 1.11 and 2.29 mg/cm, 2 respectively. Cross-sectional observation of the oxidation specimen identified a dense Cr 2 O 3 oxide layer at 1000°C condition, and the thickness of the oxide layer increased as the oxidation temperature increased. At 1100°C and 1200°C oxidation temperatures, Fe-rich oxide was also formed on the dense Cr 2 O 3 oxide layer. Based on the above findings, this study identified the high-temperature oxidation mechanism of HK30 alloy manufactured by MIM.
This study investigated the microstructure and mechanical properties of 17-4PH precipitation hardened martensite stainless steel and Fe-Cr-B based alloy mixed material manufactured using powder injection molding. 17-4PH stainless steel powder was mixed with 5 wt%, 10 wt% and 20 wt% Fe-Cr-B based alloy (M alloy) powder to manufacture three different PIM mixed materials. Initial microstructural observations confirmed the δ-ferrite phase and martensite phase in the matrix region in all three PIM mixed materials, and (Cr, Fe) 2 B phase was found in the strengthening phase, boride region. Room temperature tensile tests determined the yield strengths of the 5 wt%, 10 wt% and 20 wt% M added mixed materials to be 568.2 MPa, 674.0 MPa and 697.7 MPa, and the ultimate tensile strengths to be 1141.5 MPa, 1161.0 MPa and 1164.6 MPa, respectively. Fracture surface observation confirmed ductile fracture in the ferrite phases, and brittle fracture in the martensite phase and (Cr, Fe) 2 B phase. Also, as the M powder fraction increased, the fracture mode of the (Cr, Fe) 2 B phase was confirmed to shift from intra-phase fracture to inter-phase fracture. Based on the above-mentioned findings, the deformation and fracture behavior of new mixed materials manufactured using powder injection molding was identified, and its application possibilities were also discussed.
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