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3 Archives of Metallurgy and Materials

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Development of Admixed Lubricant for Warm Die and Warm Compaction of High-Density PM Iron

100%

Oh M. C. , Ahn B.

tom Vol. 66, iss. 3

679--682

The objective of the present research is to develop new admixed lubricants which can be used for high-density sintered iron when processed using warm die and warm compaction. Depending on various lubricants, the effect of compaction temperature on the ejection behavior and sintered properties was studied. Lubricants were prepared by mixing of Zn-stearate and ethylene bis stearamide (EBS) in various compositions. The iron powders blended with lubricants were compacted under the pressure of 700 MPa at various temperatures. The green compacts were sintered at 1120°C for 30 min. Microstructure, density, hardness, and transverse rupture strength of sintered materials with different lubricants were investigated in detail.

Microstructural Evolution of Sinter-Forged Fe-Cr-Mo-C Alloy Depending on Cu Addition

80%

Oh M. C. , Kim M. , Lee J. , Ahn B.

Archives of Metallurgy and Materials

2019

tom Vol. 64, iss. 2

539--542

Pre-alloyed Astaloy CrLTM (Fe-1.5 wt% Cr-0.2 wt% Mo), a commercial Fe-based alloy powder for high strength powder metallurgy products, was sintered and hot forged with additions of 0.5 wt% C and 0~2 wt% Cu. To investigate the influence of various Cu contents, the microstructural evolution was characterized using density measurements, scanning electron microscope (SEM) and electron backscatter diffraction (EBSD). Transverse rupture strength (TRS) was measured for each composition and processing stage. The correlation between Cu additions and properties of sinter-forged Fe-Cr-Mo-C alloy was discussed in detail.

Novel Technique to Produce Hybrid P/M Components Using Dissimilar Ferrous Alloys

80%

Oh M. C. , Seok H. , Jo Y. , Ahn B.

Archives of Metallurgy and Materials

2019

tom Vol. 64, iss. 2

613--616

The objective of the present research is to develop the novel multi-compaction technology to produce hybrid structure in powder metallurgy (P/M) components using dissimilar Fe-based alloys. Two distinct powder alloys with different compositions were are used in this study: Fe-Cr-Mo-C pre-alloyed powder for high strength and Fe-Cu-C mixed powder for enhanced machinability and lower material cost. Initially, Fe-Cu-C was pre-compacted using a bar-shaped die with lower compaction pressure. The green compact of Fe-Cu-C alloy was inserted into a die residing a half of the die, and another half of the die was filled with the Fe-Cr-Mo-C powder. Then they subsequently underwent re-compaction with higher pressure. The final compact was sintered at 1120°C for 60 min. In order to determine the mechanical behavior, transverse rupture strength (TRS) and Vickers hardness of sintered materials were measured and correlated with density variations. The microstructure was characterized using optical microscope and scanning electron microscope to investigate the interfacial characteristics between dissimilar P/M alloys.