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.

The coastal area of Republic of Korea is very clean compared to other countries. In this reason, west coastal area of our country is a good place for breeding up a fish such as shrimp. In winter season, the heating system is required for preventing shrimp death caused by freezing in the farm. The heater in the heating system for fishery's farm is operated very severe combating corrosion due to high accumulation by feeding material and high temperature in heated sea water. Almost all manufactured heaters of STS 316L and Ti material are scrapped every year due to heavy corrosion such a general and crevice corrosion. For comparing the general and galvanic corrosion in new heater material, the test material of Zirconium (Zr), Titanium (Ti) and STS 316L are tested by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), current density-time methods and microscopic examination in a 3.5% NaCl solution. The corrosion potential (Ecor) measured by potentiodynamic polarization for Zr, Ti and STS 316L reveals -198, -250 and -450mV, corrosion current density 0.5, 2.5 and 6.5μA/cm2 respectively. The film resistance measured by EIS are Zr 63,000, Ti 39,700 and 316L 3,150Ω, and the current of Zr-Ti couple is 0.03μA, whereas Zr-316L SS is 0.1μA. According to the result of this experiment in 3.5% NaCl solution, Zr is excellent corrosion resistance material than Ti and STS 316L.

Coatings composited with alumina and Perfluoro alkoxyalkane (PFA) resin were deposited on stainless steel plate (SUS304) to further improve corrosion resistance. Plate (ca. 10μm) and/or nanosize (27~43 nm) alumina used as inorganic additives were mixed in PFA resin to make alumina-fluoro composite coatings. These coatings were deposited on SUS304 plate with wet spray coating and then the film was cured thermally. According to the amount and ratio of the two kinds of alumina having plate morphology and nano size, corrosion resistance of the film was evaluated under strong acids (HF, HCl) and a strong base (NaOH). The film prepared with the addition of 5~10 wt% alumina powders in PFA resin showed corrosion resistance superior to that of pure PFA resin film. However, for the film prepared with alumina content above 10 wt%, the corrosion resistance did not improve with the physical properties, such as surface hardness and adhesion. The film prepared with plate/nanosize (weight ratio = 1/2) alumina especially enhanced the surface hardness and corrosion resistance. This can be explained as showing that the plate and the nanosize alumina dispersed in PFA resin effectively suppressed the penetration of cations and anions due to the long penetration length and fewer defects that accompany the improved surface hardness under a serious environment of 10% HF solution for over 120 hrs.

미세 조직은 SEM, FT-IR 스펙트라, 인장특성, 그리고 [NCO]/[OH]의 mole %, 입도분석에 의해 측정하였다. 친환경적인 NATM에 관한 관심이 고조됨에 따라 스테인레스같은 금속코팅에 더욱더 중요한 열경화 무용제 수지를 합성 하였다. 이 수지는 일반적 도료와 비교하여 매우 강도가 강하고 내구성이 매우 좋다. 폴리우레탄 수지는 폴리올, IPDI, 실리콘 계면활성제, 촉매, 충전제로 구성된다. 폴리우레탄 화합물은 가교제가 첨가된 수지가 가교제가 첨가되지 않은 수지보다 물성이 우수함을 나타냈다. 견고한 폴리우레탄 도료의 기계적 특성은 [NCO]/[OH]와 가교제가 증가함에 따라 강도가 증가하였다. 합성한 도료의 물성 향상은 스테인레스 산업뿐만 아니라 다양한 산업에서 폴리우레탄 고분자 수지가 강구조물의 보수보강에 많은 응용이 기대된다.

This study was carried out to investigate efficacy of aerosol sanitizer with natural antimicrobial and organic acids against Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes. The artificially inoculated pathogens on stainless steel coupon were treated with grapefruit seed extract (GFE), acetic acid,citric acid and lactic acid in model cabinet for 5 min. The number of three foodborne pathogens with individual treatment was reduced by 0.34-3.77 log units, treatment with GEF + organic acid was reduced by 1.72-3.89 log units and treatment with GEF + organic acid + alcohol was reduced by 1.46-5.05 log units. By treatment with GEF + lactic acid + alcohol in scale-up model system for 10 min. Populations of E. coli O157:H7, S. Typhimurium and L. monocytogenes were reduced by 3.42, 2.72 and 2.30 log units from the untreated control respectively. From the above result,aerosol sanitizer with natural antimicrobial agents and organic acid can be used as an environmental sanitation method with satisfying the consumer demand on safe food.

Joining of NiO-YSZ to 316 stainless steel was carried out with B-Ni2 brazing alloy (3 wt% Fe, 4.5 wt% Si, 3.2 wt% B, 7 wt% Cr, Ni-balance, m.p. 971-) to seal the NiO-YSZ anode/316 stainless steel interconnect structure in a SOFC. In the present research, interfacial (chemical) reactions during brazing at the NiO-YSZ/316 stainless steel interconnect were enhanced by the two processing methods, a) addition of an electroless nickel plate to NiO-YSZ as a coating or b) deposition of titanium layer onto NiO-YSZ by magnetron plasma sputtering method, with process variables and procedures optimized during the pre-processing. Brazing was performed in a cold-wall vacuum furnace at . Post-brazing interfacial morphologies between NiO-YSZ and 316 stainless steel were examined by SEM and EDS methods. The results indicate that B-Ni2 brazing filler alloy was fused fully during brazing and continuous interfacial layer formation depended on the method of pre-coating NiO-YSZ. The inter-diffusion of elements was promoted by titanium-deposition: the diffusion reaction thickness of the interfacial area was reduced to less than 5 compared to 100 for electroless nickel-deposited NiO-YSZ cermet.

염분분위기에서의 부식은 사용후핵연료의 중간저장 기간 동안 304 스테인레스 강재 건식저장용기의 주 열 화기구들 중 하나다. 본 연구에서는 감소정도가 서로 다른 냉연 304 스테인레스 강 시편들에 0.5wt.%의 염화 나트륨 연무를 분사시키면서 느린 변형속도시험(SSRT)과 중성염 분사시험(NSS)을 85℃와 200℃에서 수행하 였다. 85℃에서 2000 시간 동안 시험한 NSS시편의 무게 변화는 200℃에서 시험한 시편의 무게 변화와 크게 달 랐다. NSS 시편의 85℃에서 무게 감량은 미미하였지만, 냉연 감소율이 증가함에 따라서 무게 변화는 점진적으 로 감소하였다. 85℃와 200℃에서 그리고 염분분사 환경에서 가볍게 냉연 가공된 시편의 SSRT 시험으로부터얻은 항복강도와 극한 인장응력의 값은 공기 중의 값보다 약간 낮았다. 그러나 염분 분위기에서 부식으로 인 한 20% 감소 냉연시편의 강도는 더 이상 변화하지 않았다. 예비결과는 냉연 304 스테인레스 강의 질과 성능이 건식저장용기의 제작을 위한 조건에 맞는다는 것을 증명하였다. 그러나 냉연 스테인레스 강의 장기적인 성능 을 더 잘 이해하기 위해서는 염분분위기에서 이 재질의 부식거동에 관한 더 많은 연구가 필요하다.

Titanium carbonitride is more perspective materials compared to titanium carbide. It can be used in tool industry and special products because of its higher strength, abrasive wear-resistance and especially its strong chemical stability at high temperatures. We produced STS+TiCxNy composite by the spark plasma sintering for higher strength and studied the characteristics. The planar and cross-sectional microstructures of the specimens were observed by scanning electron microscopy. Characterizations of the carbon and nitride phases on the surface of composite were carried out using an X-ray diffractometer. During annealing TiCxNy particles diffusion into STS 430 was observed. After annealing, sintering isolations between particles were formed. It causes decreasing of mechanical strength. In addition when annealing temperature was increased hardness increased. Heterogeneous distribution of alloying elements particles was observed. After annealing composites, highest value of hardness was 738.1 MHV.

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.

The spot weldability of dissimilar metal joints between stainless steels (AISI316) and interstitial free (IF) steels were investigated. This study was aimed to determine the spot welding parameters for a dissimilar metal joint and to evaluate the dissimilar metal joint's weldability, including its welding nugget shape, tensileshear strength, hardness, and microstructure. The fracture surface was investigated by using a Scanning Electron Microscopy (SEM). The experimental results showed that the shape of nugget was asymmetric, in which the fusion zone of the STS316 sheet was larger due to the higher bulk-resistance. The microstructure of the fusion zone was fully martensite. In order to evaluate the microstructure further, dilution of stainless steels were calculated and imposed onto the Schaeffler diagram. The predicted microstructure from the Schaeffler diagram was martensite. In order to confirm the predicted microstructure, XRD measurements were carried out. The results showed that that initial weld nugget was composed of austenite and martensite.

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.