The present work investigated the dispersion behavior of Y2O3 particles into AISI 316L SS manufactured using laser cladding technology. The starting particles were produced by high energy ball milling in 10 min for pre- alloying, which has a trapping effect and homogeneous dispersion of Y2O3 particles, followed by laser cladding using CO2 laser source. The phase and crystal structures of the cladded alloys were examined by XRD, and the cross section was characterized using SEM. The detailed microstructure was also studied through FE-TEM. The results clearly indi- cated that as the amount of Y2O3 increased, micro-sized defects consisted of coarse Y2O3 were increased. It was also revealed that homogeneously distributed spherical precipitates were amorphous silicon oxides containing yttrium. This study represents much to a new technology for the manufacture and maintenance of ODS alloys.

This study was to evaluate the efficacy of sanitizer concentrations and treatment time against two major food-borne pathogenic microorganisms such as Escherichia coli and Staphylococcus aureus on a stainless steel surface. As a result, stainless steel, treated with 100 ppm of chlorine showed reduction of E. coli(1.56, 1.49, 1.95 log cfu/25 ㎠) and S. aureus(0.49, 0.88, 1.27 log cfu/25 ㎠) after 0, 5 and 10 min, but none was not detected in treatment with 200 ppm. The population of E. coli(0.73, 0.90, 1.55 log cfu/25 ㎠) and S. aureus(0.37, 1.00, 1.45 log cfu/25 ㎠) reduced in 35.5% ethanol treated group, but none was not detected in treatment with 70%. The population was reduced E. coli(0.28, 0.64, 1.07 log cfu/25 ㎠) and S. aureus(0.53, 0.87, 0.99 log cfu/25 ㎠) by treatment with 45.5ppm of hydrogen peroxide, but none was not detected in treatment with 91 ppm. Quarternary ammonium compound with 100 ppm was reduced E. coli(0.82, 1.62, 1.71 log cfu/25 ㎠) and S. aureus(0.46, 0.93, 1.38 log cfu/25 ㎠), but none was not detected in treatment with 200 ppm. Predictive models of sterilization for all 4 disinfectants were suitable to use with r2 value of higher than 0.94. These models may be of use to food services and manufacture of safe products by controlling E. coli and S. aureus without the need for further detection of the organisms.

To improve the chemical stability of metal, the ceramic coatings on metallic materials have attracted interest from many researchers due to the chemical inertness of ceramic materials. To endure strong acids, SiOC coating on metal substrate was carried out by dip coating method using 20wt% polyphenylcarbosilane solution; SiC powder was added to the solution at 10wt% and 15wt% to improve the mechanical properties and to prevent cracks of the film. Thermal oxidation as a curing step was carried out at 200˚C for crosslinking of the polyphenylcarbosilane, and the coating samples were pyrolysized at 800˚C under argon to convert the polyphenylcarbosilane to SiOC film. The thicknesses of the SiOC coating films were 2.36μm and 3.16μm. The quantities of each element were measured as SiO1.07C6.33 by EPMA, and it can be confirmed that the SiOC film from polyphenylcarbosilane was formed in a manner that was carbon rich. The hardness of the SiOC film was found to be 3.2Gpa through nanoindentor measurement. No defect including cracks appeared in the SiOC film. The weight loss of the SiOC coated stainless steel was within 2% after soaking in 10% HCl solution at 80˚C for one week. From these results, SiOC coating shows good potential for application to protect against severe chemical corrosion of stainless steel.

레이저 용발법에 의한 금속 표면 제염특성을 평가하였다. 레이저로는 파장 532 nm, 펄스에너지 150 mJ, 펄스폭 5 ns의 큐스위치 Nd:YAG 를 적용하였고, 금속 표면에 CsNO3, Co(NH4)2(SO4)2, Eu2O3 그리고 CeO2를 오염시켜 이들의 제염 특성을 평가하였다. 제염 변수로는 레이저 적용횟수, 레이저 에너지 밀도 및 레이저 조사 각도 특성을 평가하였으며 각각 8, 13.3 J/cm2 및 30o의 최적 조건을 확인하였다. 제염 효율은 오염성분의 비점과 관련이 있었으며 CsNO3>Co(NH4)2(SO4)2>Eu2O3>CeO2 순이었다. 또한 여러 에너지 밀도 조건에서 스테인레스 스틸 재질의 식각 깊이 제어 특성을 규명하였다.

Cubic boron nitride (c-BN) is a promising material for use in many potential applications because of its outstanding physical properties such as high thermal stability, high abrasive wear resistance, and super hardness. Even though 316L austenitic stainless steel (STS) has poor wear resistance causing it to be toxic in the body due to wear and material chips, 316L STS has been used for implant biomaterials in orthopedics due to its good corrosion resistance and mechanical properties. Therefore, in the present study, c-BN films with a B4C layer were applied to a 316L STS specimen in order to improve its wear resistance. The deposition of the c-BN films was performed using an r.f. (13.56 MHz) magnetron sputtering system with a B4C target. The coating layers were characterized using XPS and SEM, and the mechanical properties were investigated using a nanoindenter. The friction coefficient of the c-BN coated 316L STS steel was obtained using a pin-on-disk according to the ASTM G163-99. The thickness of the obtained c-BN and B4C were about 220 nm and 630 nm, respectively. The high resolution XPS spectra analysis of B1s and N1s revealed that the c-BN film was mainly composed of sp3 BN bonds. The hardness and elastic modulus of the c-BN measured by the nanoindenter were 46.8 GPa and 345.7 GPa, respectively. The friction coefficient of the c-BN coated 316L STS was decreased from 3.5 to 1.6. The wear property of the c-BN coated 316L STS was enhanced by a factor of two.

Two kinds of oxide-dispersion-strengthened (ODS) 316L stainless steel were manufactured using a wet mixing process(wet) and a mechanical alloying method (MA). An MA 316L ODS was prepared by a mixing of metal powder and a mechanical alloying process. A wet 316L ODS was manufactured by a wet mixing with 316L stainless steel powder. A solution of yttrium nitrate was dried after being in the wet 316L ODS alloy. The results showed that carbon and oxygen were effectively reduced during the degassing process before the hydroisostatic process (HIP) in both alloys. It appeared that the effect of HIP treatment on increase in impact energy was pronounced in the MA 316L ODS alloy. The MA 316L ODS alloy showed a higher yield strength and a smaller elongation, when compared to the wet 316L ODS alloy. This seemed to be attributed to the enhancement of bonding between oxide and matrix particles from HIP and to the presence of a finer oxide of about 20 nm from the MA process in the MA 316L ODS alloy.

Inorganic oxide colloids dispersed in alcohol were applied to a stainless steel substrate to produce oxide coatings for the purpose of minimizing emissive thermal transfer. The microstructure, roughness, infrared emissive energy, and surface heat loss of the coated substrate were observed with a variation of the nano oxide sol and coating method. It was found that the indium tin oxide, antimony tin oxide, magnesium oxide, silica, titania sol coatings may reduce surface heat loss of the stainless steel at 300˚C. It was possible to suppress thermal oxidation of the substrate with the oxide sol coatings during an accelerated thermal durability test at 600˚C. The silica sol coating was most effective to suppress thermal oxidation at 600˚C, so that it is useful to prevent the increase of radiative surface heat loss as a heating element. Therefore, the inorganic oxide sol coatings may be applied to improve energy efficiency of the substrate as the heating element.

자외선 살균소독기의 유효성을 검정하기 위하여 스테인리스스틸 컵 바닥에서 E. coli를 대상으로 살균력을 측정하고 살균패턴을 조사하였다. 스테인리스스틸 컵 바닥의 자외선 강도는 컵의 위치에 따라 큰 차이를 보였다. 중앙부에 놓인 컵의 바닥에서는 높은 자외선 강도를 보인 반면 외곽으로 갈수록 자외선 강도는 급격하게 약화되었으며, 이러한 편차는 상단 선반에서 가장 심하였고 중단 및 하단 선반으로 갈수록 완화되었다. E. coli를 대상으로 한 스테인리스스틸 컵 바닥에서 살균효과는 컵 바닥의 자외선 강도와 살균시간에 비례하였다. 자외선에 의한 E. coli 살균패턴은 tailing을 수반하는 의사 1차반응으로 나타났으며 각 구간의 살균속도상수를 산출한 결과 초기 살균속도상수(K1)는 위치에 따라 큰 차이를 보인 반면 후기 살균속도상수(K2)는 위치에 따른 차이가 크지 않았다. 현장에서 자외선 살균소독기를 용이하게 사용할 수 있도록 일정 살균치를 얻는데 필요한 자외선 조사시간을 산출하는 방정식을 제시하였다.

Austenitic oxide-dispersion-strengthened (ODS) stainless steel was fabricated using a wet mixing process without a mechanical milling in order to reduce contaminations of impurities during their fabrication process. Solution of yttrium nitrate was dried after a wet mixing with 316L stainless steel powder. Carbon and oxygen contents were effectively reduced by this wet processing. Microstructural analysis showed that coarse yttrium silicates of about 150 nm were formed in austenitic ODS steels with a silicon content of about 0.8 wt%. Wet-processed austenitic ODS steel without silicon showed higher yield strength by the presence of finer oxide of about 20 nm.

Austenite precipitation behavior was studied with solidification rates and alloying contents, N and Cr, in duplex stainless steels by directional solidification. Directional solidification experiments were carried out with solidification rates, 1~100mm/s, and N and Cr contents, 0~0.27wt.%, 25~28wt.% respectively, in a duplex stainless steel, CD4MCU. As the solidification rate increases, the dendrite spacing reduced and the austenite phase in the ferrite matrix became finer. The volume fraction of austenite phase increased and its shape went to be round with increasing nitrogen contents in duplex stainless alloys. The Cr alloying element, even though it is a ferrite former, showed to enhance the nitrogen solubility in the alloy and caused the austenite round and finer. Also, Cr was supposed to decrease the austenite volume fraction, but it increased the austenite slightly due to increasing nitrogen solubility during solidification.

현재 중소형선박의 동력전달용 스테인리스 추진축계가 많이 사용되고 있으나 선미를 통과하는 선미관 패킹부, 베어링이 작용하는 접촉부 등에서 마모, 축의 재질불량이나 설계 불량으로 인하여 축이 절손되는 경우가 많다. 프로펠러축이 과다마모 또는 절손으로 파단시 새로운 축으로 전환하고 있으나 축을 새것으로 구입하려면 주문, 제작 등에 따라 상당한 비용이 소요된다. 또한 축을 육성 용접하는 경우는 해양수산관청의 승인을 득하도록 되어 있으나 지금까지 승인이 된 경우가 없었다. 따라서 이 연구에서는 직접 스테인리스 재료를 육성 용접하면서 모재와 비교하여 용접에 따른 금속조직의 변화, 결함의 계측 등을 규명하여 해양수산관청의 승인에 필요한 용접 절차, 검사에 필요한 사항 등을 검토하였다.

본 논문은 인발공정에 의해서 만들어지는 스테인리스 강선의 제작 시에 필요한 인발기술에 관한 연구이다. 스테인레스 강선재는 표면이 아름답고, 표면가공을 다양하게 할 수 있으며 내식성 및 내마멸성이 우수할 뿐만 아니라 강도가 크고 가공선이 뛰어나고, 내화 내열성이 우수하여 건축물에도 많이 사용되는 볼트, 너트, 스크루우, 용접건, 와이어 로우프 등에 많이 사용된다. 대공간 연성 건축물에 특히 많이 사용되는 스테인리스 와이어의 제작 시에 최적의 다이스 설계 기준간을 찾아서 현장 적용이 용이 하도록 하였다. 스테인리스 와이어의 인발 생산 과정의 역학적 개념을 이해함으로서 와이어 로우프의 물리적 성질을 파악할 수 있다고 사료된다.