• 한국산학기술학회논문지
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• 제3권2호
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• pp.115-119
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• 2002

본 연구에서는 자이로 펌프의 내구성 및 내마모성을 향상시키고자 로타와 붓싱 재질 개선방안을 조사하였다. 질화강과 SKD11 합금 부품에 스퍼터링 방법으로 TiN Coating과 가스질화법으로 표면처리를 행하였으며, 기지조직의 개선을 위하여 SKD11 합금의 열처리를 행하였다. 실험결과 TiN Coating부품은 펌프 작동 중 Coating층의 밀착력 부족으로 박리현상이 나타났으나, 가스질화 시 우수한 표면경도와 충분한 경화층으로 뜯김현상이 제거되었다. SKD11 합금의 열처리 탄화물 조절을 위한 SKD11 합금의 열처리 결과 경도가 증가하였다.

• Tribology and Lubricants
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• 제12권4호
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• pp.60-70
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• 1996

Scuffing and severe wear of the highly stressed sliding components have been very critical problems in the development of a rotary compressor. In order to improve durability and reliability of the compressor, plasma ion-nitriding was applied on the shaft and the vane surface. The effects of different treatment conditions on the mechanical and tribological properties of the ion-nitrided surfaces were investigated. Ion-nitrided surfaces showed better tribological performances than untreated surfaces. The best wear performance was observed when the shaft was nitrided in the condition of 450$\circ$C, 7 hours, $N_2:H_2=1:4$ gas mixture by forming a ductile nitrided layer which has $\gamma'$ phase microstructure. As nitrogen gas pressure increased, $\varepsilon$ phase layer was formed. This hard phase layer was observed to be more beneficial for the vane in reducing friction and wear.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1999년도 추계학술대회 논문집 - 한국공작기계학회
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• pp.197-203
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• 1999

Stainless steels in general has passive film having strong corrosion resistance on surface. Therefore it must be necessarily removed by etching in mixing solution of sulfuric and chloric acid before Nitriding treatment. But in the ion nitriding, nitride layer was easily formed because passive film was removed without difficult by sputtering effect. The removal extent of these passive films was greatly effected by gas mixing ratios and pressure and holding times of pre sputtering factors in pre sputtering stage. As a results of experiment it has been known that pre sputtering pressure and holding time was not nearly effective on the formation behavior of nitride layer. But when A/H2 gas mixing ratios was 1/2 (vol%) was the most effective of the all pre sputtering conditions. It was resulted from the combination of mechanical reaction byArgon bombardment and chemical reaction by reduction of hydrogen on the passive film.

• 한국재료학회지
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• 제12권6호
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• pp.447-451
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• 2002

Pulsed DC-plasma nitriding has been applied to form nitride layer having only a diffusion layer. The discharge current with the variation of discharge gases is proportional to the intensity of $N_2^+$ peak in optical emission spectroscopy during the plasma nitriding. The discharge current, microhardness in surface of substrate and depth of nitride layer increased with the ratio of $N_2\;to\;H_2$ gas in discharge gases. When the ratio of $N_2\;to\;H_2$ is lower than 60% in the discharge gases, high microhardness value of 1100Hv nitride layer which contains no compound layer has been formed.

• 대한금속재료학회지
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• 제46권11호
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• pp.708-712
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• 2008

The influence of high temperature gas nitriding (HTGN) in STS347 and STS310S steels was experimentally investigated. The HTGN was carried out at $1,050^{\circ}C{\sim}1,150^{\circ}C$ for 10 hrs in a gaseous atmosphere containing $1kg/mm^2$ of nitrogen. After HTGN, fine precipitates of $Cr_2N$ and NbN appeared in austenite on the surface of STS 347, while nitrogen pearlite, which was layeredof $Cr_2N$ and austenite alternatively, appeared in austenite on the surface of STS 310S. The surface hardness of HTGN-treated, STS 347 and STS 310S specimens was 250~360 Hv and 270~400 Hv, respectively, depending on the temperature of HTGN. The nitrogen content was analyzed 1.4 wt% and 1.6 wt% at the surface layer of STS 347 and STS 310S steels, respectively. In addition, an improvement in the corrosion resistance of HTGN treated specimens was observed.

• 한국세라믹학회지
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• 제23권5호
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• pp.61-66
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• 1986

The gas mixtures ($H_2$/$N_2$, He/$N_2$) having a high thermal conductivity allow the heat generated by the nitriding exotherm to be dissipated from the compact in to the nitriding atmosphere permitting a more accurate control of temperature and produces a more uniform microstructure. In order to observe the effect of the mixed gas atmosphere on the microsturcture of RBSN. the specimen was nitrided in the mixed gas atmosphere which was containe up to 50vol% $H_2$ or He for 0-12 hrs at 135$0^{\circ}C$. The addition of hydrogen to nitrogen gas resulted in the growth of a-needle at the early stage of nitrding increase of the reaction rate and a finer and more uniform microstructure. in case of the addition of helium the behaviour of reaction was similar to the one with pure nitrogen. As the amount of helium was increased a coarse microstructure was formed.

• Journal of Advanced Marine Engineering and Technology
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• 제22권5호
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• pp.712-720
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• 1998

The effect of H2:N2 gas ratio on the case thickness hardness and nitrides formation in the sur-face of SCM440 machine structural steel have been studied by micro-pulse plasma process. The thickness of compound layer increased with the increase of nitrogen content in the gas com-position. The maximum thickness of compound layer the maximum case depth and the maximum surface hardness were about 15.8${\mu}m$, 400${\mu}m$ and Hv765 respectively in the nitriding condition of 250Pa and 70% nitrogen content at $520^{\circ}C$ for 7hrs. Generally only nitride phases such as ${\'{\gamma}}$($Fe_4N$)$\varepsilon(Fe_2}{_3N}$ phases were detected in compound and diffusion layer by XRD analysis. The amount of $\varepsilon(Fe_2}{_3N}$ phase increased with the increase of nitrogen content. The relative amounts and kind of phases formed in the nitrided case changed with the change of nitrogen content in the gas composition.

• 한국군사과학기술학회지
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• 제13권2호
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• pp.275-282
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• 2010

The improved properties of surface layer can be achieved by so-called "new salt bath nitriding(NSBN)", which has been developed by a domestic company. This process based upon modified traditional salt bath nitriding process, increased hardenability with minimum toughness deterioration. This process also offers not only less white layer surfaces but also more eco-friendly one. That is, NSBN is the new eco-friendly surface treatment technology removing harmful $CN^-$ and toxic gas. According to the research of applying NSBN to Cr-Mo-V steel which has been used in defense industry, showed the improved result of wear resistance and surface hardening than non-coated condition. In further, we expect NSBN to curtail expenses and productivity improvement applied to the various defense industry parts.

• 열처리공학회지
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• 제11권4호
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• pp.315-323
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• 1998

This study has been conducted to develope the combined heat treating technique of gas carburising - gas nitriding and gas carburising to improve the hot working performance of type H3 hot work tool steel. Case depth and carbrides coarsening were increased with increasing carburising temperature and time, respectively. Surface hardness showed decreasing tendency with increasing 2nd tempering temperature after carburising treatment. After carburising, 2nd treatment at 500 to 600 was chosen according to a hardness demand of final product. High temperature tempering resistance showed more excellent quality during such carburising-nitriding or carburising than complex treatment as after conventional hardening.

• Applied Microscopy
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• 제44권2호
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• pp.79-82
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• 2014

Aluminum nitride (AlN) powder was easily synthesized by the direct nitridation of Al melt containing ~20 wt.% Mg catalyst and the nitriding behavior was investigated by thermodynamic calculation and through observations of electron microscopy and X-ray diffraction. The addition of Mg catalyst decreased the nitriding temperature below $1,000^{\circ}C$, which is comparable to the high nitriding temperature of $1,400^{\circ}C$ required in carbothermal method. It was caused by a significant increase of the solubility of nitrogen gas due to the increase of Mg catalyst in Al melt. The dissolved nitrogen gas met Mg catalyst and was transformed into metastable $Mg_3N_2$. Finally the metastable phase reacted with Al to AlN.