• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.383-384
• /
• 2006

Fe-4Ni-0.5Mo-1Cu powder was selected as raw material, pressed and sinter-hardened at $1135\;^{\circ}C$ for 30 min with rapid cooling. The density varies in the range of $7.24-7.29\;g/cm^3$. Its fatigue properties have been tested in axial loading of alternating tensile/compressive stress at R=-1 with a servo-pulse pump. The fatigue endurance limit was measured to be 260 MPa. The microstructure showed more homogeneous bainite and martensite. Fractography displayed the fatigue cracks initiated from the pore areas near the surface. A non-typical ductile fatigue striation was found. More dimples occurred on fracture surface due to the plastic deformation, which can prohibit cracking propagation and improve its fatigue properties.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.160-161
• /
• 2006

Seasonal changes have been recognized in particle characteristics and forming characteristics of iron powder with insulated coating for a compacted magnetic core because of its high hygroscopicity, due to its phosphate coating and resin binder additives. For this reason, particle characteristics and molding characteristics of the powder with diverse water absorbtivity have been studied. The result shows that the higher the volume of absorbed water, the worse the fluidity becomes, resulting in the reduction in both springback during the molding process and expansion reduction after the heat treatment. The requirement on dimension accuracy for the finished product can be satisfied with an additional drying process on the material powder, which contributes to maintain its water volume constant.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.195-196
• /
• 2006

In recent years, demands for sintered ferrous material with higher strength are increasing. To satisfy these demands, studies and commercial use of the die wall lubrication method, the warm compaction method and the combination of both methods are widely carried out to achieve high density. The die wall lubrication warm compaction method makes it possible to achieve high density by reducing internal lubricant through die wall lubrication, although the method involves several issues such as prolonged cycle time due to lubricant spraying and difficulty in spraying lubricant in the case of compacting with complicated geometry. Meanwhile, the conventional warm compaction method requiring no die wall lubricant application cannot achieve such a high density as in the case of die wall lubrication warm compaction due to higher volume of internal lubricant. However, this report discloses our study result in which the possibility of improving density is exhibited by using a lubricant type with superior dynamic ejection property that can reduce volume of lubricant additive.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2001년도 추계학술강연 및 발표대회
• /
• pp.38-39
• /
• 2001

• 한국결정성장학회지
• /
• 제10권3호
• /
• pp.264-270
• /
• 2000

소결광을 구성하는 광물상(hematite, magnetite, calcium ferrite, slag)들을 X선 내부표준법을 이용하여 정량분석을 하였다. 분석에는 표준물질로 NaF와 SiO$_2$를 선택하여 교정곡선을 작성하여 내부표준법에 적용하였다. 소결광내에 존재하는 calcium ferrite는 순수 CF(CaO.$Fe_2$$O_3$에 X선 회절피크는 나타나지 않았으며, 순수 $CF_2(CaO.$2Fe_2$$O_3$)에 근접하였으나 CF2에 소량의 $Al_2$$O_3$와 $SiO_2$가 고용된 4원계($Fe_2$$O_3$-CaO-$AI_2$$O_3$-$SiO_2$)에 보다 더 근접한 것으로 나타났다. 합성소결광의 정량분석은 두 표준물질 모두 상대오차가 $\pm$5 wt% 내에서 일치하였다. 실제 소결광의 정량분석결과 hematite는 27~40 wt%, magnetite는 20~30 wt%, calcium ferrite 22~33 wt%, slag 10~20 wt% 범위에서 분포하였다.

• 자연과학논문집
• /
• 제8권1호
• /
• pp.53-59
• /
• 1995

Alumina 세라믹스의 기계적 물성 증진을 위하여 SiC whisker로 강화시키고 소결 조제 및 소결 온도의 영향을 고찰하였다. Whiker의 소결억제 효과로 인하여 고상소결을 촉진하는 MgO나 $TiO_2$를 소결조제로 사용한 경우에서는 치밀한 소결체를 얻을 수 없었으나, 액상을 형성하는 $Y_2O_3$를 2wt% 첨가한 경우에 양호한 소결밀도를 얻을 수 있었다. whisker 첨가에 의한 기지의 기계적 물성의 증진 효과도 함께 얻을 수 있었다. 강화 효과는 보강재인 whiker 자체의 보강 효과와 함께 입성장 억제 효과가 복합적으로 작용한 것으로 판단되었다. 소결체를 HIP 처리한 경우에는 거의 이론 밀도까지 이르는 아주 치밀한 소결체의 제조가 가능하였으며, 기계적 물성은 상압소결 후의 결과에 비하여 향상됨을 확인할 수 있었다.

• 한국분말재료학회지
• /
• 제30권6호
• /
• pp.484-492
• /
• 2023

In this study, Ni-Y₂O₃ powder was prepared by alloying recomposition oxidation sintering (AROS), solution combustion synthesis (SCS), and conventional mechanical alloying (MA). The microstructure and mechanical properties of the alloys were investigated by spark plasma sintering (SPS). Among the Ni-Y₂O₃ powders synthesized by the three methods, the AROS powder had approximately 5 nm of Y₂O₃ crystals uniformly distributed within the Ni particles, whereas the SCS powder contained a mixture of Ni and Y₂O₃ nanoparticles, and the MA powder formed small Y₂O₃ crystals on the surface of large Ni particles by milling the mixture of Ni and Y₂O₃. The average grain size of Y₂O₃ in the sintered alloys was approximately 15 nm, with the AROS sinter having the smallest, followed by the SCS sinter at 18 nm, and the MA sinter at 22 nm. The yield strength (YS) of the SCS- and MA-sintered alloys were 1511 and 1688 MPa, respectively, which are lower than the YS value of 1697 MPa for the AROS-sintered alloys. The AROS alloy exhibited improved strength compared to the alloys fabricated by SCS and conventional MA methods, primarily because of the increased strengthening from the finer Y₂O₃ particles and Ni grains.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2000년도 특별강연 및 춘계학술발표대회 개요집
• /
• pp.185-188
• /
• 2000

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.517.2-517.2
• /
• 2006

• 한국분말재료학회지
• /
• 제9권3호
• /
• pp.189-198
• /
• 2002

In this work, transient liquid phase (TLP) bonding of Ni-Cr heat resisted cast alloy (HP) was investigated. And also the behaviors of the solid particles distributed in the interlayer during TLP bonding were investigated. The MBF-60 and solid particles (Ni, Fe, and $Al_2O_3$ powders respectively) added MBF-60 which will be a liquid phase coexisting with solid particles at the bonding temperature were used as insert metal. The effective and sound bonding was possible by spark plasma sinter-bonding due to the differences of electric resistance between base metal and liquid insert layer which creates high temperature region. During the isothermal solidification, $Al_2O_3$ particles and solid particles of liquid phase sintered insert metal have shown no growth, while Ni and Fe particles grow rapidly. In this TLP bonding using the MBF-60 and distributed Fe, Ni particles as insert materials, the whole isothermal solidification process was dominated by the growth rate of the solid particles distributed in the interlayer.