• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 춘계학술대회 논문집
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• pp.385-388
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• 2009

Dry-sliding-wear behavior of Fe-18Cr-l0Mn steel with various carbon and nitrogen contents was characterized, and the effect of carbon and nitrogen contents on the wear was investigated. Dry sliding wear tests of the steel were carried out at room temperature against an AISI 52100 bearing steel ball using a pin-on-disk wear tester. Applied wear loads were varied from 10 N to 100 N, and the sliding distance was fixed as 720 m. Worn surfaces and the wear debris of the steel were examined using an SEM to find out the wear mechanism. It was found that the Fe-18Cr-10Mn with both carbon and nitrogen exhibited superior wear resistance to the steel with only nitrogen. The wear resistance of the Fe-18Cr-10Mn-xC-yN alloy increased with the increase of the carbon content. The excellent wear resistance of the Fe-18Cr-10Mn-xC-yN alloy was explained by the increased strain-hardening capability with the interstitial atoms.

• 동력기계공학회지
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• 제9권1호
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• pp.76-81
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• 2005

The effect of micro-pulse plasma nitriding temperature and time on the case thickness, hardness and nitride formation in the surface of Fe-12Cr-22Mn-X alloy with 3% Co and 1% Ti alloys elements investigated. External compound layer and internal diffusion layer was constituted in plasma nitride case of Fe-12Cr-22Mn-X alloys and formed nitride phase such as ${\gamma}'-Fe4N\;and\;{\varepsilon}-Fe2-3N$. Case depth increased with increasing the plasma nitriding temperature and time. Surface hardness of nitrided Fe-12Cr-22Mn-X alloys obtained the above value of Hv 1,600 and case depth obtained the above value of $45{\mu}m$ in Fe-12Cr-22Mn-3Co alloy and $60{\mu}m$ in Fe-12Cr-22Mn-1Ti alloy. Wear-resistance increased with increasing plasma nitriding time and showing the higher value in Fe-12Cr-22Mn-1Ti alloy than Fe-12Cr-22Mn-3Co alloy.

• 열처리공학회지
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• 제7권3호
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• pp.206-218
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• 1994

In 50%$NH_3+Air+N_2$ atmospheres, the effect of air additions on the growth characteristics of the compound layer during oxynitriding at $570^{\circ}C$ for 2hr in carbon and alloy steels has been investigated. The ammount of apparent residual ammonia during oxynitriding has shown to be increased with air additions(9~36 Vol. %) and X-ray diffraction analysis of case oxynitreded has shown that the compound layer consist of ${\varepsilon}-Fe_{2-3}$(N, C) phase and ${\gamma}^{\prime}-Fe_4$(N,C) phase. In the case of carbon steels, the thickness of oxide layer, compound layer and porous layer and the amount of ${\varepsilon}-Fe_{2-3}$(N,C) phase in the compound layer were increased with additions of air in 50%$NH_3+N_2$ atmospheres. At the same gas composition, the thickenss of oxide layer, compound layer and porous layer in alloy steels showed slightly thin layer thickness compared to those of carbon steels and the ${\gamma}^{\prime}-Fe_4$(N,C) phase in the compound layer of alloy steels was found barely. Therefore, the most obvious effect of air addition in the gas nitriding atmosphere has been found to in crease further kinetics of nitriding reaction.

• 한국표면공학회지
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• 제36권6호
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• pp.480-490
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• 2003

Effects of plasma-nitriding on the pitting corrosion of Fe-30at%Al-5at%Cr alloy containing Ti, Hf, and Zr were investigated using potentiostat in 0.1M HCl. The specimen was casted by the vacuum arc melting. The subsequent homogenization was carried out in Ar gas atmosphere at $1000^{\circ}C$ for 7days and phase stabilizing heat treatment was carried out in Ar gas atmosphere at $500^{\circ}C$ for 5 days. The specimen was nitrided in the $N_2$, and $H_2$, (1:1) mixed gas of $10^{-4}$ torr at $480^{\circ}C$ for 10 hrs. After the corrosion tests, the surface of the tested specimens were observed by the optical microscopy and scanning electron microscopy(SEM). For Fe-30at%Al-5Cr alloy, the addition of Hf has equi-axied structure and addition of Zr showed dendritic structure. For Fe-30at%Al-5Cr alloy containing Ti, plasma nitriding proved beneficial to decrease the pitting corrosion attack by increasing pitting potential due to formation of TiN film. Addition of Hf and Zr resulted in a higher activation current density and also a lower pitting potential. These results indicated the role of dendritic structure in decreasing the pitting corrosion resistance of Fe-30Al-5Cr alloy. Ti addition to Fe-30Al-5Cr decreased the number and size of pits. In the case of Zr and Hf addition, the pits nucleated remarkably at dendritic branches.

• 소성∙가공
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• 제8권3호
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• pp.247-247
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• 1999

The segregation (distribution) of nickel and the composition of its constituents influence the low thermal expansion characteristics (Invar effect) in Fe-30 wt.% Ni-12.5 wt.% Co-xC Invar alloy. The change of coefficient of the thermal expansion and magnetic properties were studied as an aspect of carbon addition causing the segregation of Ni in primary austenite of as-cast Fe-30 wt.% Ni-12.5 wt.% Co Invar alloy. The coefficient of thermal expansion of Fe-30 wt.% Ni-12.5 wt.% Co-xC Invar alloy showed its lowest value at 0.08 wt.% carbon, increased with increasing carbon content in the range of 0.08-1.0 wt.%C, kept constant at 1.0-2.0 wt.%C and decreased at carbon higher than 2.0 wt.%. The effective distribution of the coefficient of nickel in as-cast Fe-30 wt.% Ni-12.5 wt.% Co-xC Invar alloy increased with increasing carbon content. The volume fraction of they phase of Fe-30 wt.% Ni-12.5 wt.% Co-xC alloy increased with increasing carbon content. The microstructure of Fe-30 wt.% Ni-12.5 wt.% Co-xC alloy changed with the carbon content was independent of the coefficient of thermal expansion. The Curie temperature changed linearly with the carbon content and was similar to the change of the coefficient of thermal expansion. Moreover, the coefficient of thermal expansion decreased when the ratio of saturation magnetization to Curie temperature ($\sigma_s/T_c$) increased, decreasing the Curie temperature and showed a specific relationship with the magnetic properties of the Fe-30 wt.% Ni-12.5 wt.% Co-xCInvar alloy.

• Journal of Magnetics
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• 제6권4호
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• pp.122-125
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• 2001

Phase relationships of the HDDR (hydrogenation, disproportionation, desorption and recombination)-treated Sm$_3$(Fe,M)$_{29}$-type alloy with chemical composition of Sm$_{9}$Fe$_{65}$ $Co_{20}$V$_{6}$ were studied by X-ray diffraction (XRD) and by thermomagnetic analysis (TMA). The alloy was disproportionated into a mixture of $SmH_{x}$ and $\alpha$-Fe at high temperature under hydrogen gas. The disproportionated material was recombined into a mixture of Sm-(Fe,M) (M = Co and/or V) and $\alpha$-Fe phases. The structure of the Sm-(Fe,M) phase was dependent upon the recombination conditions, and a detailed phase diagram showing the phase relationships in the HDDR-treated alloy has been established. The Sm-(Fe,M) phase in material recombined above $900^{\circ}C$ had the $Sm_2Fe_{17}$-type structure, and it exhibited the $SmFe_{7}$-type structure when recombined at temperatures ranging from $700^{\circ}C$ to $850^{\circ}C$. Recombination below $650^{\circ}C$ led to the $SmFe_3$-type structure of the Sm-(Fe,M) phase. Curie temperatures of the Sm-(Fe,M) phases in the recombined material were significantly higher than those of the corresponding stoichiometric phases. It was suggested that the chemical composition of the Sm-(Fe,M) phases may be significantly different from that of the corresponding stoichiometric phases. All the HDDR-treated $Sm_{9}Fe_{65}Co_{20}V_{6}$ materials showed the soft magnetic features regardless of the phase constitution.n.

• 한국자기학회지
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• 제12권1호
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• pp.30-33
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• 2002

초미세결정렵 Nd-Fe-B-Mo-Cu합금에서 Co 치환이 미세조직과 자기특성에 미치는 영향을 조사 하였다. 급속응고법으로 제조된 비정질 Nd-(Fe, Co)-B-Mo-Cu합금은 결정화에 의하여 $\alpha$-Fe기 초미세결정립 Nd-(Fe, Co)-B-Mo-Cu합금이 제조되었다. Co로의 Fe치환은 결정립 미세화에 기여하며, 이로 인하여 경자기특성이 개선되었다. 최적열처리된 초미세결정립 N $d_4$(F $e_{0.85}$ $Co_{0.15}$)$_{82}$ $B_{10}$M $o_3$Cul합금의 잔류자화, Curie온도는 Co가 치환되지 않은 합금에 비하여 개선된 우수한 특성을 나타내었다. 64$0^{\circ}C$, 10분 열처리된 초미세결정립 N $d_4$(F $e_{0.85}$ $Co_{0.15}$)$_{82}$ $B_{10}$M $o_3$Cu 합금의 평균결정립 크기는 약 15 nm이며, 이때 보자력, 잔류자화 및 최대에너지적은 각각 239kA/m, 1.4 T 및 103.5 kJ/ $m^3$이었다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.425-428
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• 2009

Aerospace engine application needs to stand high temperature and pressure. Because of its mechanical properties such as high strength at high temperature, Alloy 718 is used aerospace engine application about 80%. But alloy 718's mechanical properties cause some problem to manufacturing profile ring like damage of material and mold. In this study, alloy 718's mechanical properties investigated for knowing its formability and using FE-Simulation for designing profile ring roll process and mold shape. Profile ring rolling processing is designed with "Initial material$\rightarrow$Blank$\rightarrow$Linear Ring$\rightarrow$Profilering". Blank's heating temperature is setting $1100^{\circ}C$ for manufacturing a trial profile ring on the basis of FE-Simulation. As a result of manufacturing alloy 718 profile ring, it is possible to make near target profile shape ring with all of the processing condition which gives in this study.

• 한국자기학회지
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• 제8권3호
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• pp.125-130
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• 1998

13Cr-1.5Nb-Fe합금분말이 수분사법으로 제조되엇다. 제조된 합금뷴말을 압축기를 이용하여 ring현상으로 성형한후, 진공중에서 소결하였다. as-prepared 분말의 현상, 입도분포, 성분분석 및 포화자화물 조사하였으며, 소결된 시편의 투자율, 교류자기이력손실이 조사되었다. as-prepared 13Cr-1.5Nb-Fe합금분말의 포화자화는 160emu/g이었으며, 산소함유량은 약 600ppm이었다. 입도분포는 약 70$\mu$m에서 50%vol.을 나타낸다. 교류투자율은 소결온도 및 성형온도가 증가할수록 증가한다. 주파수 20KHz에서 교류자기이력손실은 12ton/cm2성령압력 및 120$0^{\circ}C$ 소결온도 조건에서 107W/cc로 가장우수하다.

• 한국진공학회지
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• 제6권S1호
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• pp.53-58
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• 1997

It is well known that the equiatomic FeAl alloy crystallizes in a paramagnetic CsCl structure and is very stable in a wide temperature range owing to a significant charge transfer from Al to Fe. A presence of structural defects normally enhances the magnetic and magneto-optical properties of this alloy. In this study spin-resolved photoemission and magnetic circular dichroism (MCD) were carried out on both ordered and disordered $Fe_{0.52}Al_{0.48}$ alloy films. The disordered state in the alloy films was obtained by a vapor quenching deposition on cooled substrates. It is shown that the order-disorder transition in the Fe0.52Al0.48 alloy films leads to a significant change in the spin polarization. Form the MCD results the orbital and spin magnetic moments of the constituent atoms are obtained. According to the sum rule the spin and orbital magnetic moments of Fe in the disordered FeAl film are $\mu\frac{SR}{spin}=0.8\mu_B$ and $\mu\frac{SR}{orb}=0.14\mu_B$ respectively. The spin magnetic moment is also evaluated to be $\mu\frac{BR}{spin}=0.77\mu_B$ by the branching ration method employing a photon polarization of 90%.