• Journal of Advanced Marine Engineering and Technology
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• v.22 no.5
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• pp.702-711
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• 1998

The characteristics of corrosion resistance for the surface of medium high carbon steels and low alloy steels utilizing as manufacturing the machinery structures and machining tools and treating by plasma/ion nitriding process have been studied in terms of electrochemical polarization behav-iors including corrosion potential(Ecorr) anodic polarization trends and polarization resistance(Rp) The seven base materials showed a clear passivation behavior for the polarization tests in the ASTM standard solution 1N ${H_2){SO_4}$ Although the treated surface by plasma nitriding for the seven test materials showed a significant increase in hardness the treatment gave a detri-mental effect in corrosion resistance. The various characteristics including corrosion potential polarization curves microstructures corrosion current polarization resistance among non-treat-ed nitriding and/or soft-nitriding treated specimens have been investigated and some of the mechanisms discussed.

• Korean Journal of Metals and Materials
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• v.48 no.3
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• pp.225-234
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• 2010

Salt bath nitriding, which has been developed recently by domestic company, is an emerging ecofriendly surface treatment. The salt bath nitriding is accompanied by the electrolysis process in the pretreatment step, and this whole processis called Pseudo-Electrolysised Salt bath Nitriding (PESN). The PESN creates only $NH_3$ and non-toxic salts without harmful $CN^{-}$ or toxic gas such as that found in previous salt bath nitriding. In general, ion nitriding and gas nitriding create high hardness and a strong brittle white layer on the surface. However, the PESN shows a thin white and gray layer. The PESN was applied to the defense material, 3%Cr-Mo-V steel, to study the surface characteristics at $480^{\circ}C$, $530^{\circ}C$, and $580^{\circ}C$ for 4 hrs, 20 hrs, 40 hrs, and 60 hrs of nitriding time condition. As a result, the best nitriding layer was found at $530^{\circ}C$ for 40 hrs. If we improve corrosion resistance and nitriding layer depth, the PESN will be able to be applied to the defense industry parts.

• Journal of the Korean institute of surface engineering
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• v.29 no.6
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• pp.615-620
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• 1996

Chromium-Molybdenum steel was plasma-nitrided at 823 K for 10.8 ks in an atmosphere of 30% $N_2$-70% $H_2$ gas under 665 Pa without and with a subsidiary cathode of $MoS_2$ to compare ion-nitriding and plasma-sulfnitriding using subsidiary cathode. When the steel was ion-nitrided without $MoS_2$, iron nitride layer of 4$\mu\textrm{m}$ and nitrogen diffusion layer of 400mm were formed on the steel. A compound layer of 15$\mu\textrm{m}$ and nitrogen diffusion layer of 400$\mu\textrm{m}$ were formed on the surface of the steel plasma-sulfnitrided with subsidiary cathode of $MoS_2$. The compound layer consisted of FeS containing Mo and iron nitrides. The nitrides of $\varepsilon$-$Fe_2$, $_3N$ and $\gamma$-$Fe_4N$ formed under the FeS. The thicker compound layer was formed by plasma-sulfnitriding than ion-nitriding. In plasma-sulfnitriding, the surface hardness was about 730 Hv. The surface hardness of the steel plasma-sulfnitrided with $MoS_2$ was lower than that of ion-nitrided without $MoS_2$. This may be due to the soft FeS layer formed on the surface of the plasma-sulfnitrided steel.

• Corrosion Science and Technology
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• v.22 no.4
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• pp.221-231
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• 2023

Interest in aluminum alloys for the hydrogen valves of fuel cell electric vehicles (FCEVs) is growing due to the reduction in fuel efficiency by the high weight. However, when an aluminum alloy is used, deterioration in mechanical characteristics caused by hydrogen embrittlement and wear is regarded as a problem. In this investigation, the aluminum alloy used to prevent hydrogen embrittlement was subjected to surface treatments by performing hard anodizing and plasma ion nitriding processes. The hard anodized Al alloy exhibited brittleness in which the mechanical characteristics rapidly deteriorated due to porosity and defects of surface, resulting in a decrease in the ultimate tensile strength and modulus of toughness by 15.58 and 42.51%, respectively, as the hydrogen charging time increased from 0 to 96 hours. In contrast, no distinct nitriding layer in the plasma ion-nitrided Al alloy was observed due to oxide film formation and processing conditions. However, compared to 0 and 96 hours of hydrogen charging time, the ultimate tensile strength and modulus of toughness decreased by 7.54 and 13.32%, respectively, presenting excellent resistance to hydrogen embrittlement.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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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.

• Journal of the Korean Society for Heat Treatment
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• v.7 no.3
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• pp.184-189
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• 1994

The heat treatment charaterristic of SCM 440 and B 16 steels has been investigated in various condition(A, B and C) to the effect of heat treatment on mechanical properties, and the following results were obtained. 1. We are obtained a good nitriding characteristic in bainitic structure than other heat treatment cycle in our experiment. 2. Fatigue characteristic has shown in order of B)C)A condition as heat treatment cycle. 3. The effective hardening depth and fatigue characteristic has been excellented in B 16 than SCM 440 after the nitriding and Q. T for Band C condition. 4. Nitriding depth has been increased in addition of Cr, V and the nitriding efficiency is increased as easiness of banite formation to wide range of cooling rate by addition of Mo. 5. The depth of compound layer in parallel surface, notched slop plane and notched bottom has been varied to the nitriding depth of 5, 4 and 3 ${\mu}$ in relatively uniform pattern after 10h nitriding treatment for SCM 440 into A condition.

• Journal of the Korean institute of surface engineering
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• v.30 no.2
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• pp.144-154
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• 1997

Effects of plasma nitriding on the surface charcteristice of stainless steel(SS) were investjgated by utilizing wear tester, micro-hardness tester and potentiostat. The surface and corrosion morphology of plasma nitrided SS were analyzed by utilizing optical microscopy, SEM, XRD and WDX. It was found that plasma nitriding at $550^{\circ}C$, compared with $380^{\circ}C$, prodiced a good wear resistance and hardness as nitriding time increased, whereas Mo addition showd that were resistance and hardness decreased. Intergranular corrosion(IGC) resistance improved significantly in the case of plasma nirtrided SS containing 4.05wt% Mo at $380^{\circ}C$ because that nitrogen and Mo ast syner gidically to form a protective layer on surface which is responsible for the aggresive SCN-ion. Plasma nitrided at $550^{\circ}C$ decreased IGC as Mo content increased. Pitting improved in the plasma nitirided SS at Mo content incresased owing to retard a nucleation and growth of chromium carbide or nitirde in grain boundary.

• Journal of the Korean institute of surface engineering
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• v.54 no.6
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• pp.307-314
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• 2021

Diamond-like carbon (DLC) is difficult to achieve sufficient adhesion because of weak bonding between DLC film and the substrate. The purpose of this study is to improve the adhesion between substrate and DLC film. DLC film was deposited on AISI H13 using linear ion source. To improve adhesion, the substrate was treated by dual post plasma nitriding. In order to define the mechanism of the improvement in adhesive strength, the gradient layer between substrate and DLC film was analyzed by Glow Discharge Spectrometer (GDS) and Scanning Electron Microscope (SEM). The microstructure of the DLC film was analyzed using a micro Raman spectrometer. Mechanical properties were measured by nano-indentation, micro vickers hardness tester and tribology tester. The characteristic of adhesion was observed by scratch test. The adhesion of the DLC film was enhanced by active screen plasma nitriding layer.

• Transactions of the Korean Society of Mechanical Engineers
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• v.3 no.3
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• pp.98-103
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• 1979

The fatigue limit of an ion-nitrided steel was investigated experimentally and analytically. It is found that fatigue limit can singificantly be increased by ion-nitriding, and that the case depth is the most important parameter which determines the fatigue limit. The data indicate that fatigue limit increases with the case depth as well as the surface hardness of the nitrided steel. The fracrographs of the fracture surfaces taken by a scanning electron microscope show that the fisch-eye is located at the subsurface of failed specimens. Assuming that crack propagates from the subsurface inclusions, an analytical model is proposed to predict the fatigue limit. Taking into account the stress distrbution of a nitrided specimen, fatigue limit is predicted as a function of the case depth. The proposed semiemprical formula agrees satisfactorily with the experimental data obtained from rotating beam fatigue testing.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.3
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• pp.217-223
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• 1984

An attempt is made to predict the wear behavior of ion-nitrided metal, when wear arises from asperity interactions. The analysis demonstrates that wear mechanisms are not inconsistent with observed behavior, indicates and approaches to a better appreciation of the effects of such factors as nitrided layer formation and surface topographical features. It was found on ion-nitriding that penetration rate and case development are faster and wear properties of the final product are more improved than conventional gas and salt-bath methods of nitriding.