• Korean Journal of Materials Research
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• v.9 no.11
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• pp.1102-1107
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• 1999

FeAl matrix composite was fabricated successfully by hot-pressing. The mechanical properties of FeAl alloys have been widely studies, but their behaviors of surface hardening effect by plasma nitriding has not yet been studied. This study was to analysis the relationship between microstructure of the sintered composite by hot-pressing and surface hardening at plasma nitriding treatment. Surface hardening of FeAl base alloys was improved by plasma nitriding with increasing plasma treatment time. Excellent surface hardness in the FeAl alloys could be obtained by plasma nitriding($\textrm{H}_{\textrm{v}}$ 100gf, diffusion layer: 1100~1450kg/$\textrm{mm}^2$, matrix : 330~360kg/$\textrm{mm}^2$). Diffusion layer size increased with increasing plasma nitriding times and decreased with increasing Sic, content.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.05a
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• pp.268-268
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• 2009

고밀도 유도 결합 플라즈마를 이용한 연료 전기 분리판용 질화 장치를 플라즈마를 모사할 수 있는 3차원 전산 유체 역학 프로그램인 CFD-ACE+를 이용하여 해석하였따. 내장형 안테나 타입의 유도 결합 플라즈마의 전자 온도, 밀도 균일성, 가스 유동, 얇은 기판이 촘촘히 적재 되었을 경우의 플라즈마 특성을 모사하였다.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.3
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• pp.238-244
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• 2017

Plasma ion nitriding has been widely used in various industries to improve the mechanical properties of materials, especially stainless steels by increasing the surface hardness. It has the particular advantages of less distortion compared to that in the case of hardening of steel, gas nitriding, and carburizing; in addition, it allows treatment at low-temperatures, and results in a high surface hardness and improved corrosion resistance. Many researchers have demonstrated that the plasma ion nitriding process should be carried out at temperatures of below $450^{\circ}C$ to improve corrosion resistance via the formation of the expanded austenite phase(S-phase). Most experimentals studied to date have been carried out in chloride solutions like HCl or NaCl. However, the electrochemical characteristics for the chloride solutions and natural seawater differ. Hence, in this work, plasma ion nitriding of 304 stainless steels was performed at various temperatures, and the electrochemical characteristics corresponding to the different process temperatures were analyzed for the samples in natural seawater. Finally the optimum plasma ion nitriding temperature that resulted in the highest corrosion resistance was determined.

• Journal of the Korean Society for Heat Treatment
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• v.14 no.1
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• pp.8-16
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• 2001

The effects of gas composition, pressure, temperature and time on the case thickness, hardness and nitride formation in the surface of tool steels(STD11 and STD61) have been studied by micro-pulse plasma nitriding. External compound layer and internal diffusion layer and the diffusion layer were observed in the nitrided case of tool steels. The relative amounts and kind of phases formed in the nitrided case changed with the change of nitriding conditions. Generally, only nitride phases such as ${\gamma}(Fe_4N)$, ${\varepsilon}(Fe_{2-3}N)$, or $Cr_{1.75}V_{0.25}N_2$ phases were detected in the compound layer, while nitride and carbide phases such as ${\varepsilon}-nitride(Fe_{2-3}N)$, $(Cr,Fe)_{\gamma}C_3$ or $Fe_3C$ were detected in the diffusion layer by XRD analysis. The thickness of compound layer increased with the increase of nitrogen content in the gas composition. Maximum case depth was obtained at gas pressure of 200Pa.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.3
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• pp.187-196
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• 1995

TiN and AlN are ceramic materials with mechanical and chemical properties for use in structural applications at elevated temperature. The purpose of this research is to develop the technology for the synthesis of (Ti, Al)N power, which shows simultancously the excellent properties of TiN and AlN, from the mixed powder($Ti_{0.25}Al_{0.75}$, $Ti_{0.5}Al_{0.5}$ and $Ti_{0.75}Al_{0.25}$) by the direct nitriding method. The effects of variables such as temperature, mixing ratio of Al to Ti in raw material were investigated. The(Ti, Al)N powder can be easily synthesized from the mixed powder by the direct nitriding method. Among the mixed powdres, the nitriding behavior decreased with increasing the ratio of Al to Ti. This behavior is well explained by the nitriding mechanism presented in this research.

• Journal of the Korean institute of surface engineering
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• v.34 no.3
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• pp.231-239
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• 2001

The structure and composition of Cr-nitrides formed on an electroplated hard Cr layer during an ionnitriding process was analyzed, and the growth kinetics of the Cr-nitrides was examined as a function of the ion-nitriding temperature and time in order to establish a computer simulation model prediction the growth behavior of the Cr-nitride layer. The Cr-nitrides formed during the ion-nitriding at $550~770^{\circ}C$ were composed of outer CrN and inner $Cr_2$N layers. A nitrogen diffusion model in the multi-layer based on fixed grid FDM (Finite Difference Method) was applied to simulate the growth kinetics of Cr-nitride layers. By measuring the thickness of each Cr-nitride layer as a function of the ion-nitriding temperature and time, the activation energy for growth of each Cr-nitride was determined; 82.26 KJ/mol for CrN and 83.36 Kj/mol for $Cr_2$N. Further, the nitrogen diffusion constant was determined in each layer; $9.70$\times$10^{-12}$ /$m^2$/s in CrN and $2.46$\times$10^{-12}$ $m^2$/s in $Cr_2$N. The simulation on the growth kinetics of Cr-nitride layers was in good agreements with the experimental results at 550~72$0^{\circ}C$.

• Korean Journal of Materials Research
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• v.12 no.6
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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.

• 연구논문집
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• s.26
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• pp.121-132
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• 1996

The carburising surface modification treatment of the die steel has been used for improving wear resistance and heat cycle strength of the die and preventing a pitting on the surface because the carbides are forming in the matrix during carburising. Generally, the hot forging die was used after quenching-tempering treatment or nitriding after quenching-tempering treatment. The nitriding after carburising on the surface of a hot die steel and a wear resistance die steels was suggested by SOUCHARD, JACQUOT. and BUVRON. This surface modification treatment improved the adhesive and abrasive wear resistance and friction coefficient. The process was introduced to the forging die of stainless steel, titanium alloy steel, alloy and medium carbon steel and the physical properties of the die after the treatment were improved. The surface hardening treatment of the nitriding, the carburising, the boriding, and TD process were used to improved the life time of the forging die. Also, the coating process of PVD, CVD and PCVD were used and the hard chromium plating was occasionally used. Therefore, this study analyzed the effects of the carburising time and the conditions of nitriding on STD61 steel. The case depth, the surface hardness, the forming carbide size and shape during overcarburising process on the die steel were also examined.

• Journal of the Korean Society for Heat Treatment
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• v.9 no.3
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• pp.219-227
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• 1996

The purpose of this research is to develop the technology for the synthesis of (Ti,Al)N powder, which shows simultaneously the excellent properties of TiN and AlN, from the Ti-Al intermetallic compounds by the direct nitriding method. The effects of variables such as temperature, Ti-Al intermetallic compounds ($TiAl_3$, TiAl and $Ti_3Al$) were investigated by TG, XRD and SEM. The (Ti,Al)N powder can be easily synthesized from the intermetallic compounds by the direct nitriding method. Among the intermetallic compounds, the nitriding behavior increased with TiAl> $Ti_3Al$ > $TiAl_3$, as the difference of diffusion coefficient for nitrogen in each materials. The ternary nitride such as $Ti_2AlN$ and $Ti_3Al_2N_2$ can be synthesized by the direct nitriding method, although the ternary nitride coexist with TiN and AlN. The ternary nitrides are stable below $1400^{\circ}C$, but these are gradually decomposed into TiN and AlN above $1400^{\circ}C$.

• Journal of the Korean institute of surface engineering
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• v.44 no.5
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• pp.190-195
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• 2011

Diamond-like carbon (DLC) has many outstanding properties such as low friction, high wear resistance and corrosion resistance. However, it is difficult to achieve enough adhesion on the metal substrates because of weak bonding between DLC film and the metal substrate. The purpose of this study is to enhance an adhesion of DLC film. For improving adhesion, the substrate was treated by active screen plasma nitriding before DLC film deposing. Nitrided substrates were investigated by Glow Discharge Spectrometer (GDS), Micro-Vickers Hardness. DLC films were deposited on several metals by linear ion source, and characteristics of the films were investigated using nano-indentation, Field Emission Scanning Electron Microscope (FESEM). The adhesion was measured by scratch tester. The adhesion of DLC films was increased when nitriding layer was formed before DLC deposition. Therefore, the adhesion of DLC film can be enhanced as increasing the hardness of materials.