• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1996년도 춘계학술대회
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• pp.133-136
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• 1996

We investigated how hydroxyapatite (HA) coating onto a porous super stainless steel (S.S.S, 22Cr-20Ni-6Mo-0.25N) affects bone ingrowth in a dog transcortical femoral model. Implants were histologically evaluated after 4 and 48 weeks of implantation, and the bone bonding strength at the bone/implant interface was examined by employing the pull-out test. The direct osseous tissue bonding onto the HA-coated S.S.S was observed, but the uncoated stainless steels had thin fibrous tissue layers. The mean interface strength of the HA-coated S.S.S was 1.5 and 2.5 times greater than those of the S.S.S and the 316L SS after one year of implantation, respectively. In preliminary studies, no toxic responce was observed from a cytotoxicity test of the S.S.S, having similar corrosion resistance to titanium. Our results suggest that early osteoconductive nature of HA coating may induce long term osteointegration for a bioinert substrate.

• 한국정밀공학회지
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• 제26권9호
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• pp.121-126
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• 2009

Stainless steel 316L (STS 316L) is widely used as a material of biopsy needle. However it has a side effect that tissue can be damaged by electrochemical operation between tissue and STS 316L. Many studies have been made on the ceramic coating of biopsy needle to reduce the side effect. In this study, STS 316L was coated with three bioceramics, $Al_2O_3$, $SiO_2$ and $ZrO_2$ using a RF magnetron sputtering method. The effects of ceramic coating on the electrical conductivity and coating strength of ceramic-coated STS 316L were investigated. The results showed that the electrical conductivity of ceramic-coated STS 316L was much lower than that of uncoated STS 316L. The coating strength of $ZrO_2$-coated STS 316L was 30% and 70% higher, respectively than those of $Al_2O_3$-coated STS 316L and $SiO_2_3$-coated STS 316L.

• 비파괴검사학회지
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• 제10권1호
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• pp.47-55
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• 1990

This paper presents experimental results which explore the capability of a CW laser speckle photography for tile measurement of in-plane displacement at high temperature. The serious restrictions on the application of the method seem to be the ambient air turbulence and the change of surface texture caused by the oxidation, as they tend to decorrelate the double exposured speckle patterns. In order to assess only the effect of air turbulence, a ceramics-coated stainless steel plate is heated in air and Ar-laser specklegrams are made with combination of temperature and lateral translation displacement. The slight reduction in visibility of Young's fringes is observed at $1000^{\circ}C$. The analyses of Young's fringes are carried out by a image processing system using a TV-camera and computers, and the result agrees well with the micrometer reading. Futhermore, uncoated stainless steel and Hastelloy X plates are tested and the effect of oxidation is also evaluated. The experimental results demonstrate that a CW laser speckle photography is applicable at temperatures up to $1000^{\circ}C$.

• 소성∙가공
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• 제32권5호
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• pp.247-254
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• 2023

This study conducted the wear tests on bending punches coated with PVD CrN and examined the surface quality of the product formed by each punch in the forming of uncoated TRIP1180 sheets. The study quantitatively estimated the surface quality of the product by measuring the roughness and imaging the product surface. The correlation between the punch wear depth and the product surface roughness was quantitatively analyzed. The results showed that before failure occurs, the product roughness was comparable with that of the as-received, and the product surface was smooth without scratches and defects. However, after failure, the punch wear is caused by fretting wear mechanism, and a punch whose coating is not completely peeled plows the product surface, resulting in severe scratches with grooves and ridges on the product surface. Severe wear on the punch surface caused by fretting wear can rapidly degrade the product surface quality as it is directly affected by the punch surface condition, and the product surface quality accurately reflects the punch wear condition.

• Journal of Electrochemical Science and Technology
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• 제6권2호
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• pp.65-74
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• 2015

This work examines the characterization and corrosion behaviour of laser alloyed UNSG10150 steel with three different premixed composition Zn-Sn binary powders using a 4.4 kW continuous wave (CW) Rofin Sinar Nd:YAG laser processing system. The steel alloyed samples were cut to corrosion coupons, immersed in sulphuric acid (0.5 M H₂SO₄) solution at 30℃ using electrochemical technique and investigated for its corrosion behaviour. The morphologies and microstructures of the developed coated and uncoated samples were characterized by Optic Nikon Optical microscope (OPM) and scanning electron microscope (SEM/EDS). Moreover, X-ray diffractometer (XRD) was used to identify the phases present. An enhancement of 2.7-times the hardness of the steel substrate was achieved in sample A₁ which may be attributed to the fine microstructure, dislocations and the high degree of saturation of solid solution brought by the high scanning speed. At scanning speed of 0.8 m/min, sample A₁ exhibited the highest polarization resistance R_p (1081678 Ωcm² ), lowest corrosion current density i_corr (4.81×10⁻⁸A/cm² ), and lowest corrosion rate Cr (0.0005 mm/year) in 0.5 M H₂SO₄. The polarization resistance R_p (1081678 Ωcm² ) is 67,813-times the polarization of the UNSG10150 substrate and 99.9972% reduction in the corrosion rate.

• 한국산업융합학회 논문집
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• 제15권4호
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• pp.103-109
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• 2012

To enhance the cutting performance of high speed steel(HSS) endmill, single and multilayer coating is applied on the substrated of the HSS endmill. Coating material reduces cutting force and enhances resistance against abrasive wear. This paper presents the physical vapour deposition(PVD) coating technology and evaluate the PVD coated HSS endmill. The performance of coated HSS endmills are fifteen times better than uncoated HSS endmill on proposed cutting conditions. The TiAlN monolayer coated endmills(futura nano coating) are better than those of multilayer coated endmills(futura coating) on machined surface and tool wear.

• 한국산업융합학회 논문집
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• 제16권4호
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• pp.119-125
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• 2013

To enhance the cutting performance of high speed steel(HSS) endmill, single and multilayer coating is applied on the substrated of the HSS endmill. Coating material reduces cutting force and enhances resistance against abrasive wear. This paper presents the physical vapour deposition(PVD) coating technology and evaluate the PVD coated HSS endmill. The performance of coated HSS endmills are fifteen times better than uncoated HSS endmill on proposed cutting conditions. The TiAlN monolayer coated endmills(futura nano coating) are better than those of multilayer coated endmills(futura coating) on machined surface and tool wear.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.307-310
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• 2005

The effects of deformation properties on the bond of steel reinforcing bars to concrete are experimentally studies to expect the lap splice strength. Based on the previous research about relative rib area, lap splice strength between reinforcing bars and concrete can be improved by the control of rib height and spacing. This paper describes the testing and analysis of 15 beam-spliced specimens containing D25, D22, D19 with relative rib areas ranging from 0.066 to 0.162. The tests are analyzed to determine the effect of relative rib area(Rr) on the increase in bond strength. The tests also provide a preliminary indication of the effect of high relative rib area on the splice strength of uncoated bars.

• 한국기계가공학회지
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• 제16권5호
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• pp.55-62
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• 2017

The grate bar, a component used in steel mills, is used in harsh environments where external disturbances such as high temperature, abrasion, corrosion, and impacts are present. Therefore, in this study, spray-coating was performed on the most severely affected surface to extend the lifetime of the grate bar. The thermal and mechanical properties of the sprayed coated bars were investigated based on the performances under abrasion, thermal shock, tension, and sand blasting, and the microstructures by microscope. By analyzing the thermal and mechanical properties of the uncoated original grate bar and coated grate bar and comparing them with one another, the physical performance improvement of the coated grate bar can be verified.

• 한국정밀공학회지
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• 제3권2호
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• pp.62-75
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• 1986

An experimental investigation of the machining characteristics such as cutt- ing resistance, surface roughness and tool wear in turning the test pieces of SM45C steel with both coated and uncoated carbide tool tips under various cutting conditions was conducted. Also a specially designed simple vibration damping device was experimentally evaluated for its effectiveness on machined surface roughness and a vibration test was conducted to confirm its ability to reduce the amplitude. Based on these tests finding, the following conclusions are made; 1. The cutting resistance($\textrm{p}_{1}$) increases as the depth of cut(d) increases at fixed feed rate(f) over the cutting speed(v) range of 43-226 m/min and p decreses about 18% average when V is increased for fixed d and f. At V= 226m/min, $\textrm{p}_{1}$/for A, C tips are about the same level but $\textrm{p}_{1}$ for B tip is 15% less than A, C tips. 2. The specific cutting resistance(Ks) at V=226 m/min was derived for A, B, C tips respectively and the value of Ks for B rip is about 20% less than A, C tips. 3. The surface roughness(Ra) improves significantly as the cutting speed(V) is increased and this effect was greater when V>100 m/min. On the other hand, Ra deteriorates as the feed rate(f) is increased and this trend was accelerated when f>0.3 mm/rev. With regard to the difference of Ra values among A, B, C tips, at V=226m/min, d=0.4mm, and f=0.31-0.61mm/rev, Ra values for B.C tips are about 17% less than tip A. 4. The experimental tool wear equations were derived for A, B, C tips and from these equations, the tool life($\textrm{T}_{\textrm{L}}$) baced on the I.S.O. criteria was calculated to be $\textrm{T}_{\textrm{L}}$<$\textrm{T}_{\textrm{LB}}$<$\textrm{T}_{\textrm{LC}}$ for both flank wear($\textrm{V}_{\textrm{B}}$) and boundary wear($\textrm{V}_{\textrm{N}}$). Hence, the coated tips are superior to the uncoated tip and tip C is considered to be the best. 5. The cutting resistance may be slightly reduced and the surface rounghness improved when the damper is used especially when V>100 m/min. Therefore this damping device is considered to be effective and practical. The experimental surface roughness equations were also derived. Based on the vibration test, it is established that the surface roughness improvement was the result of amplitude reduction made possible by the damper.