• 한국표면공학회지
• /
• 제37권1호
• /
• pp.53-57
• /
• 2004

Austenitic stainless steel AISI 304 was nitrided in a low-pressure RF plasma using pure nitrogen. With a treatment of time of 4.0h at $400^{\circ}C$, the nitrogen-rich layer on the sample was $3\mu\textrm{m}$thick and had a hardness of approximately 4.4 times higher than that of untreated material. XRD data showed that as the process temperature rose from 350∼$450^{\circ}C$, the expanded austenite peaks became more prominent while the austenite peaks became weaker. Expanded austenite was transformed to ferrite and CrN at the treatment of$ 500^{\circ}C$. Langmuir probe measurements showed that electron density decreased above $450^{\circ}C$.

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2000년도 추계학술발표회 초록집
• /
• pp.13-14
• /
• 2000

• 열처리공학회지
• /
• 제11권2호
• /
• pp.99-110
• /
• 1998

The effects of pre-heat treatment(Q/T) on microstructure and hardness of SCM435 structural steel nitrided by micro-pulse plasma was investigated. The quenching and tempering temperatures for obtaining matrix hardness of SCM435 steel on range of HRC30 to HRC40 desired for machine parts were about $860^{\circ}C$ and $500^{\circ}C$ respectively. The case depth of SCM435 nitrided at $480^{\circ}C$ for 5 hours was independent of pre-heat treatment condition and was approximately $150{\mu}m$. However, hardness and compactness of nitrified layer on Q/T treated specimen were more heigher than annealed specimen. The case depth increased linearly with the increase of nitriding temperature, however, the hardness of nitrified layer decreased with the temperature. Phase mixture of ${\gamma}^{\prime}$-phase($Fe_4N$) and ${\varepsilon}$-phase($Fe_3N$) were detected by XRD analysis in the nitrified layer formed at optimum nitriding condition, and only single ${\gamma}^{\prime}$-phase was detected in the nitrified layer formed at higher nitriding temperature such as $540^{\circ}C$. The optimum nitriding temperature was approximately $480^{\circ}C$ which is lower than tempering temperature for preventing softening behavior of SCM435 matrix during nitriding process and the surface hardness of nitrified layer obtained by optimum preheat treatment condition was about Hv930.

• 열처리공학회지
• /
• 제5권4호
• /
• pp.215-223
• /
• 1992

This study has been performed to investigate into some effects of temperature, gas mixing ratio and time on the optical microstructure, hardness and wear characteristics of medium carbon alloy steel treated by plasma nitriding. The results obtained from the experiment are summarized as follows: (1) Optical micrographs of AISI 4140 steel plasma-nitrided by the double stage technique have revealed that the nitrided layer is composed of the compound layer and the diffusion layer. The variation in temperature at the first stage gives effects, on the formation of compound layer and the growth rate is shown to be relatively fast at $460^{\circ}C$. (2) The thickness of compound layer has been found to increase with increasing nitrogen percentage in the gas mixture and the holding time. It is therefore recommended that a shorter holding time and a lower nitrogen percentage are more effective to produce a tougher compound layer and a diffusion layer only. (3) X-ray diffraction analysis for AISI 4140 steel has shown that the compound layer consist of ${\gamma}^{\prime}-Fe_4N$ and ${\alpha}-Fe$ and that tough compound layer diffustion layer only can be obtained by the double stage plasmanitriding process. (4) There is also a tendency that the total hardened layer depth increases with increasing temperature, time and nitrogen percentage in the first stage during the double stage plasma nitriding. (5) The wear resistance of plasma nitrided specimens has been found thobe considerably increased compared to the untreated specimens and the amount of increment has appeared to increase further with increasing nitriding temperature, holding time and notrogen percentage of gas mixture in the first stage treatment.

• 한국표면공학회지
• /
• 제50권4호
• /
• pp.272-276
• /
• 2017

The response of AISI 310 type austenitic stainless steel to the novel low temperature plasma carburizing process has been investigated in this work. This grade of stainless steel shows better corrosion resistance and high temperature oxidation resistance due to its high chromium and nickel content. In this experiment, plasma carburizing was performed on AISI 310 stainless steel in a D.C. pulsed plasma ion nitriding system at different temperatures in $H_2-Ar-CH_4$ gas mixtures. The working pressure was 4 Torr (533Pa approx.) and the applied voltage was 600 V during the plasma carburizing treatment. The hardness of the samples was measured by using a Vickers micro hardness tester with the load of 100 g. The phase of carburized layer formed on the surface was confirmed by X-ray diffraction. The resultant carburized layer was found to be precipitation free and resulted in significantly improved hardness and corrosion resistance.

• 한국표면공학회지
• /
• 제32권3호
• /
• pp.253-256
• /
• 1999

Wet plating has been initiated and developed as a major surface finishing technology as of the long customized and highly productive process until now. As the external compression by virtue of the environmental preservation becomes stricter, there has been new move to adapt dry plating line instead of conventional wet plating one in domestic surface finishing industry. Dry plating, so-called, plasma surface technology has been developed in semiconducting industry and becomes a key technology to be useful as an alternative to wet plating in surface finishing industry. The historical progress of domestic surface finishing industry was outlined with the background on the adaptation of three dry plating processes-plasma spraying, plasma nitriding and ion plating. The present status of domestic industrial activity was covered on major alternative to wet plating.

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2014년도 추계학술대회 논문집
• /
• pp.294-295
• /
• 2014

스크린 플라즈마 기술은 저온에서 가열과 동시에 플라즈마에 의한 확산층을 형성할 수 있는 매우 큰 장점을 가진 기술이다. 특히 저합금강의 내부 경도 저하를 최소화 한 상태에서 표면경도를 올려 플라스틱 금형강 등에 이를 적용할 수 있는 연구를 진행하였고, 이에 대한 결과를 보고하고자 한다.

• 열처리공학회지
• /
• 제4권4호
• /
• pp.1-14
• /
• 1991

In PECVD(Plasma-Enhanced Chemical Vapor Deposition) process, titanium nitride is thin and its adhesion is poor for the protective coatings. Therefore it has been studied that intermediate layer forms between substrate and TiN thin film. Using R.F. plasma nitriding, nitride layer was first formed, then TiN thin film coated by PECVD. The chemical composition of the coatings has been characterized using AES, EDS and their crystallographic structure by means of XRD. Mechanical properties such as microhardness and film adhesion have also been determined by vickers hardness test, scratch test and indentation test. As a result, there was no difference in chemical composition and structure between the TiN deposition only and the composite of TiN deposition on nitrided steel. It was found that nitrided substrate increased the hardness of TiN coatings and was beneficial in preventing the plastic deformation in the substrate. Therefore the effective load bearing capacity of the TiN coatings on nitrided steel was increased and their adhesion was improved as well. According to the results of this study, the processes that lead to the formation of composite layers characterized by good working properties, i.e., high microhardness, adhesion and resistance to deformation.

• Design & Manufacturing
• /
• 제13권1호
• /
• pp.13-18
• /
• 2019

The size and prospects of the domestic semiconductor equipment market are increasing every year. In the case of various parts used inside semiconductor equipments, high durability such as high strength and abrasion resistance is demanded. Particularly, the gases used in semiconductor production processes are toxic. In order to prevent such toxic gas leakage, a precision processing technique and a surface treatment technique for preventing corrosion are required. Electro-polishing is an electro-chemical method of polishing a metal surface to make it smooth and polished. Electro-polishing is mainly used in the finishing process of metal surface. Unlike mechanical polishing, electro-polishing is used in many fields, such as fine chemical etching equipment, since no damaged layer or burr, fine polishing groove and particles are generated. However, in order to withstand the gas used in the semiconductor equipment, the parts must have high corrosion resistance. However, the surface hardness generally become lowered through electro-polishing. Therefore, in this study, surface hardness were experimentally observed before and after electro-polishing. Then, a method of improving hardness by preparing a nitrided layer by plasma ion nitriding treatment.

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2014년도 추계학술대회 논문집
• /
• pp.29-29
• /
• 2014

최근 화석에너지 고갈 및 에너지 수요의 폭발적 팽창을 해결하기 위하여 경량화와 내마모 측면에서 고효율 시스템을 적용한 자동차 및 각종 성형 기기들이 개발되고 있다. 특히 장치의 고성능화라는 요구조건을 충족시키기 위해서는 금속가공산업에서 표면개질의 중요성이 부각되고 있다. 이러한 표면개질에는 일반적으로 표면의 성질을 개선하여 마모(abrasion) 및 국부 압력(local stress) 또는 피로(fatigue), 마식(wear and corrosion)에 견디게 하여 부품의 수명증대와 제품의 소형화에 기여하고 있다. 이러한 표면개질법에는 경질의 물질을 표면에 코팅시켜 재료표면의 특성을 향상시키는 방법과 금속의 표면에 다른 원소를 침투 및 확산시키는 방법으로 나눌 수 있다. 확산방법으로 침탄, 질화, 보로나이징, 크마이징 처리 방법 등이 있다. 상업적으로 가장 많이 사용되는 표면 개질법은 침탄기술로서, 고온에서 짧은 시간내에 물성 향상이 가능하지만, 강의 변태점 이상의 온도에서 진행됨으로서, 변형에 따른 문제가 발생되어 후처리를 필요로 하는 문제점을 가지고 있다. 반면, 질화법은 변태점 이하의 저온에서 철강 표면에 N을 침투시켜 강을 경화시키는 특징을 가진다. 변형이 적고 질소원자가 강내에 침투함으로 인해 내마모성, 내피로성, 내식성 등의 물리적 성질을 향상시키는 점에서 유리하여 각종 정밀 부품 및 자동차 부품, 금형 등에 많이 사용된다. 또한, 경도 향상 및 결정구조의 영향으로 코팅처리시 모재와 코팅 층의 밀착력 향상을 가져오면 이러한 이유로 코팅 층의 하지 층으로써 각광 받고 있다. 본 발표에서는 플라즈마 질화의 이해를 높이기 위해 관련 기술에 대한 전반적인 소개와 향후 플라즈마 질화 기술의 적용이 기대되는 침탄대체 적용 가능 부품, 침류질화 기술, PECVD 공정과의 접목 등 산업적은 응용 측면에서 응용 분야에 대한 소개를 진행하고자 한다.