• Journal of Ocean Engineering and Technology
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• v.25 no.1
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• pp.56-60
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• 2011

A low temperature plasma carburizing process was performed to AISI 304L austenitic stainless steel to achieve the enhancement of surface hardness without a compromise in their corrosion resistance. Attempts were made to investigate the influence of the processing temperatures on the surface-hardened layer during low temperature plasma carburizng in order to obtain the optimum processing conditions. The expanded austenite (${\gamma}C$) was formed on all the treated surfaces. Precipitates of chromium carbides were detected in the hardened layer (C-enriched layer) only for the specimen treated at $500^{\circ}C$. The hardened layer thickness of ${\gamma}C$ increased up to about $35\;{\mu}m$, with increasing treatment temperature. The surface hardness reached about 1000 $HK_{0.05}$, which is about 4 times higher than that of the untreated sample (250 $HK_{0.05}$). Minor loss in corrosion resistance was observed for the specimens treated at temperatures of $310^{\circ}C-450^{\circ}C$ compared with untreated austenitic stainless steel. Particularly, the precipitation of chromium carbides at $500^{\circ}C$ led to a significant decrease in the corrosion resistance.

• Advances in materials Research
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• v.5 no.2
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• pp.67-80
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• 2016

The objective of the present work is to optimize process parameters namely, cutting speed, feed rate, and depth of cut in milling of AISI 304 stainless steel. In this work, experiments were carried out as per the Taguchi experimental design and an $L_{27}$ orthogonal array was used to study the influence of various combinations of process parameters on surface roughness (Ra) and material removal rate (MRR). As a dynamic approach, the multiple response optimization was carried out using grey relational analysis (GRA) and desirability function analysis (DFA) for simultaneous evaluation. These two methods are considered in optimization, as both are multiple criteria evaluation and not much complicated. The optimum process parameters found to be cutting speed at 63 m/min, feed rate at 600 mm/min, and depth of cut at 0.8 mm. Analysis of variance (ANOVA) was employed to classify the significant parameters affecting the responses. The results indicate that depth of cut is the most significant parameter affecting multiple response characteristics of GFRP composites followed by feed rate and cutting speed. The experimental results for the optimal setting show that there is considerable improvement in the process.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2001.11a
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• pp.69-69
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• 2001

We report a study of the nitriding of the martensitic grade of stainless steel AKSK 420 in a low-pressure rl discharge using pure nitrogen. Much studied samples of the austenitic grade AISI 304 were treated at the same time to provide a comparison. With a treatment time of 4.0 h at $400^{\circ}C$, the nitrogen-rich layer on MSK 420 is 20pm thick and has a hardness about 4.3 times higher than that of the untreated material. The layer thickness is much greater than that obtained on AISI 304 under identical treatment conditions, reflecting the different Cr content of the two alloys. The alloy AlISI 420 is more susceptible than AISI 304 to the formation of CrN and ferrite, and this has a deleterious effect on the hardnes, gain. Below the temperature at which CrN forms, the treated layer retains its martensitic structure, but with a larger lattice parameter than the bulk, a phase that we term expanded martensite, by analogy with the situation with austenitic stainless steel. The fact that the treated layer retains a martensitic structure is interesting in view of previous evidence that nitrogen is an austenite stabilizer.

• Tribology and Lubricants
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• v.39 no.2
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• pp.43-48
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• 2023

In this study, we investigate the tribological behavior of AISI 304 stainless steel pairs under deionized water and hexagonal boron nitride (h-BN) water dispersion lubrication. The specimen friction and wear properties are evaluated using a reciprocating ball-on-flat tribometer. The coefficient of friction remains nearly constant throughout the test under both lubricant conditions. The wear depth of the specimens under h-BN lubrication is smaller than that under deionized water lubrication, indicating the inhibition behavior of h-BN nanolubricants on direct metal-metal contacts. Optical micrographs and stylus profilometer measurements are performed to evaluate the severity of damage caused by the sliding motion and to determine the wear morphology of the specimens, respectively. The results show that h-BN nanolubricants does not have a significant effect on the friction behavior but demonstrates reduced wear owing to their trapping effect between the sliding interfaces. Moreover, scanning electron microscopy and energy-dispersive X-ray spectroscopy images of the specimens were acquired to confirm the trapping effect of h-BN between the sliding interfaces. The results also suggest that the trapped lubricants can distribute the contact pressure, reducing the wear damage caused by the metal-metal contact at the interface. In conclusion, h-BN nanolubricants have potential as an anti-wear additive for lubrication applications. Further investigation is needed to provide direct evidence of the trapping effect of h-BN nanoparticles between the sliding interfaces. These findings could lead to the development of more efficient and effective lubricants for various industrial applications.

• Proceedings of the Korean Vacuum Society Conference
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• 2008.08a
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• pp.320-320
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• 2008

• Proceedings of the KWS Conference
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• 1992.10a
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• pp.180-183
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• 1992

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.2
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• pp.45-51
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• 2000

This study proposes that analysis and evaluation method of time series ultrasonic signal using the chaotic feature extrac-tion for degradation extent. Features extracted from time series data using the chaotic time series signal analyze quantitatively material degradation extent. For this purpose analysis objective in this study if fractal dimension lyapunov exponent and strange attractor on hyperspace. The lyapunov exponent is a measure of the rate at which nearby trajectories in phase space diverge. Chaotic trajectories have at least one positive lyapunov exponent. The fractal dimension appears as a metric space such as the phase space trajectory of a dynamical syste, In experiment fractal(correlation) dimensions and lyapunov experiments showed values of mean 3.837-4.211 and 0.054-0.078 in case of degradation material The proposed chaotic feature extraction in this study can enhances ultrasonic pattern recognition results from degrada-tion signals.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.04a
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• pp.120-121
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• 2007

스테인리스강을 침탄 또는 질화처리 하면 내식성이 크게 떨어진다. 하지만 처리 온도를 충분히 낮게 하면 내식성의 저하 없이 표면 경도를 증가시킬 수 있다. 침탄처리 후 질화 처리를 연속적으로 수행하면, 두꺼운 경화층을 가지고, 침탄처리한 표면보다 높은 경도를 가질 수 있다. 이 논문에서는 침탄처리 후 질화 처리시, Ar을 주입하여 질화층 형성에 주는 영향을 조사 하였다. Ar의 양이 20%보다 낮은 경우 석출물이 거의 형성되지 않았으며, Ar의 양이 증가할수록 표면경도도 증가하였다.

• Proceedings of the KWS Conference
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• 2008.05a
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• pp.32-32
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• 2008

• 한국전기화학회:학술대회논문집
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• 1998.10a
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• pp.56-56
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• 1998