• Title/Summary/Keyword: Surface Heat Treatment

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Microsstructure of Sputter-Deposited and Annealed Cu-Cr, Cu-Ti Alloy Films on Polyimide Substrate and Their Adhesion Property (폴리이미드에 스퍼터 증착한 Cu-Cr, Cu-Ti 합금박막의 열처리 전후의 접착력과 미세구조)

  • 서환석;김기범
    • Journal of the Korean institute of surface engineering
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    • v.27 no.5
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    • pp.261-272
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    • 1994
  • Both Cu-Cr and Cu-Ti alloy films with different composition were prepared by dc magnetron sputtering onto polyimide substrate and their adhesion and microstructure were observed. In addition, the effect of heat treatment at $400^{\circ}C$ for 2 hours on the variation of adhesion properties and on the changess of microstructure were investigated. Cu-Cr alloy films have crystalline structure of either for or bcc phase depending on the composition of the film. However, the Cu-Ti alloy film forms fcc phase at low Ti concentration while it forms an amorphous phase as the Ti concentration in the films is increased to more than 25at.%. TEM analysis reveal that the microstructure of Cu-Cr and Cu-Ti films forms an open structure with vacant spaces. The adhesion between Cu-Cr, Cu-Ti alloy films and polyimide substrate is relatively good before the heat treatment, but is noticeably reduced after the heat treatment. In particular, the adhesion strength is significantly reduced in the Cu-Ti alloy films after the heat treatment. The reduction of adhesion strength after the heat treatment is identified to relate with the formation of oxide phases at the metal/polyimide interface by AES(Auger Electron Spectroscopy).

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Effect of the Heat treatment and Boron on the Hot Corrosion Resistance of the Al Diffusion Coating (Al 확산피복층의 고온 내식성에 미치는 후열처리와 B첨가의 영향)

  • 김태원;윤재홍;이재현;김현수;변응선
    • Journal of the Korean institute of surface engineering
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    • v.32 no.1
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    • pp.67-77
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    • 1999
  • The Ni base superalloy Mar-M247 substrate was aluminized or aluminized after boronizing by the pack cementation under Ar atmosphere. The hot corrosion resistance and after-heat-treatment effect of aluminized specimens were studied by the cyclic hot corrosion test in $Na_2SO_4$-NaCl molten salt. XRD analysis showed that the $Ni_2Al_3$ phase was formed between the coated layer and substrate below 1273K but the NiAl phase above 1273K. The peak of the NiAl phase was developed after heat treatment. Corrosion test showed that corrosion resistance of the specimen with the NiAl phase was better than that with the $Ni_2Al_3$ phase. Corrosion resistance could be improved by heat treatment to form ductile NiAl phase, where cracks were not formed by thermal shock on coating layer. Moreover, it appeared that heat treatment played a role to improve corrosion resistance of Al diffusion coating above 1273K. The existence of boron in the Al diffusion coating layer obstructed outwared diffusion of Cr from the substrate, and it influenced on corrosion resistance of the coating layer by weakening adherence of the oxide scale.

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Surface Alloying of Iron Base Rapid Solidification Materials Using Laser Beam (레이저 빔을 이용한 철계 급랭 응고 재료의 표면 합금화)

  • Nam, K.S.;Lee, K.H.
    • Journal of the Korean Society for Heat Treatment
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    • v.9 no.4
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    • pp.229-233
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    • 1996
  • This work has been carried out to reduce the softening of heat affected zone on laser surface alloying. Iron based rapid solidification material with $Cr_{5-10}$, $V_{1-3}$, $Mo_{3-7}$, $W_{2-5}$, $B_{7-8}$, $C_{2-3}$, $Si_{0.5-1}at%$ was alloyed on the surface of SM45C steel. The excellent softening resistance in alloyed and heat affected zone showed, which could be attributed to the formation of stable high temperature precipitates.

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The Microstructure Changes of Continuous Cast iron Rods According to the Heat-Treatment Conditions (열처리 조건에 따른 주철연속주조봉의 미세조직 변화)

  • Kim, Tae-Bong;Kim, Seon-Hwa;Park, Sang-Jun
    • Journal of Korea Foundry Society
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    • v.20 no.3
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    • pp.173-180
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    • 2000
  • The microstructure changes of the matrix and the graphites were observed by optical microscope and the average hardness number was investigated according to the heat-treatment conditions of the cast iron rods by the horizontal continuous casting process in 35 mm diameter. The three kinds of heat-treatments were introduced. The first treatment was performed at 900, 950, and $1000^{\circ}C$ for 2 hours and the second treatment was conducted during 5, 10, and 15 hours at $1000^{\circ}C$ respectively. The third treatments were the two-cyclic heat-treatment and the three-cyclic heat-treatment at $1000^{\circ}C$ during 2 hours. The matrix microstructure of the specimens to be treated at various temperatures for 2 hours was the ferrite to be transformed from the pearlite The hardness number of the center of the samples according to the heat treatment time at $1000^{\circ}C$ was higher than that of the surface area because of the martensite formation in the center. Also, in the cyclic heat-treatments, the hardness number of the two-cycle treatment specimens increased because of the martensite formation in the center.

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Effects of Thermal Treatments on Microstructural Features and Magnetic Properties of Rapidly Quenched Fe-6.5%Si Strip (열처리에 따른 급냉 Fe-6.5%Si 스트립의 미세구조 및 자기특성 변화)

  • Sung, Jin-Kyung;Kim, Mun-Chul
    • Journal of Korea Foundry Society
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    • v.15 no.4
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    • pp.397-407
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    • 1995
  • The objectives of this study are first, to expand our understanding of relationship between magnetic properties and microstructural features such as grain size and texture, and second to reduce core loss of Fe-6.5%Si strip through optimizing heat treatment conditions. A rapid solidification technique, planar flow casting(PFC), was adopted to produce Fe-6.5%Si strips. The strips were heat treated under various conditions. The results show that heat treatment conditions can change not only grain size but also (200) texture formation on the strip surface. Variation in magnetic properties of Fe-6.5%Si strip is analyzed in terms of the change in grain size as well as (200) texture on the strip surface. The heat treatment conditions of $1100^{\circ}C$ over 2 hr or $1150^{\circ}C$ $1{\sim}2hr$ in $N_2+5%H_2$ appear to minimize core loss of Fe-6.5%Si strips.

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Laser Hardening of Piston Ring Groove (피스톤 링그루브의 레이저 열처리)

  • Song, Y.K.;Suh, S.
    • Journal of the Korean Society for Heat Treatment
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    • v.10 no.3
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    • pp.165-171
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    • 1997
  • Laser hardening for the piston ring groove of ductile cast iron was tried. Mechanical and microstructural investigation for the hardened area indicated that the laser heating technique could replace conventional induction hardening process completely and further showed that post grinding process would be eliminated by minimizing bulging of heat treated area. In laser hardening, the volume increase caused by martensitic phase transformation proved to be less than $10{\mu}m$, which insures no post machining on the hardened surface. As expected, the depth of hardening was inversely proportional to the beam scanning velocity and the highest surface hardness was obtained at the beam velocity of 0.75m/min. Heat treatment using phosphate coating demonstrated quite comparable result to the case of graphite suscepter.

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The heat treatment characteristics of plasma sprayed ZrO$_2$-Y$_2$O$_3$ coatings (플라즈마 용해법에 의한 ZrO$_2$-Y$_2$O$_3$ 피복층의 가열처리효과)

  • 정병근;김한삼;김수식
    • Journal of the Korean institute of surface engineering
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    • v.27 no.1
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    • pp.12-18
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    • 1994
  • The plasma spray process was used to deposit coatings of $ZrO_2$-8wt%Y2O3 powders on mild steel sub-strate, and the characteristics of as-deposited and heat treated coatings have been investigated. Particulary, the variations of porosity, wear resistance, thermal barrier and thermal shock resistance in $ZrO_2$-8wt% $Y_2O_3$coatings after heat treatment under vacuum circumstance have been investigated. The porosity of the coating layer was increased with increased spray distance. In the case of the arc current of 450A and at the spray distance of 50mm, it was obtained the lowest amount of porosity. After heat treatment, the amount of porosity was found to be decreased, and the wear resistance, microhardness and thermal shock resistance were im-proved. However, the thermal barrier was decreased.

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Effect of Cementite Precipitation on Carburizing Behavior of Vacuum Carburized AISI 4115 Steel (진공침탄에 의한 AISI 4115강의 침탄 거동에 미치는 세멘타이트 석출의 영향)

  • Gi-Hoon Kwon;Hyunjun Park;Yoon-Ho Son;Young-Kook Lee;Kyoungil Moon
    • Journal of the Korean Society for Heat Treatment
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    • v.36 no.6
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    • pp.402-411
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    • 2023
  • In order to examine the effect of cementite precipitated on the steel surface on the carburizing rate, the carburizing process was carried out at various boost times to measure the mass gain and carbon flux, phase analysis and carbon concentration analysis were performed on the surface of the carburized specimen. In the case of the only boost type, the longer the boost time, the more the mass gain by the diffused carbon follows the parabolic law and tends to increase. In particular, as the boost time increased, the depth of cementite precipitation and the average size of cementite on the steel surface increased. At a boost time of 7 min, the fraction of cementite precipitated on the surface is 7.32 vol.%, and the carburizing rate of carbon into the surface (surface-carbon flux) is about 17.4% compared to the calculated value because the area of the chemical (catalyst) where the carburization reaction takes place is reduced. The measured carbon concentration profile of the carburized specimen tended to be generally lower than the carbon concentration calculated by the model without considering precipitated cementite. On the other hand, in the pulse type, the mass gain by the diffused carbon increased according to the boost time following a linear law. At a boost time of 7 min, the fraction of cementite precipitated on the surface was 3.62 vol.%, and the surface-carbon flux decreased by about 4.1% compared to the calculated value. As a result, a model for predicting the actual carbon flux was presented by applying the carburization resistace coefficient derived from the surface cementite fraction as a variable.

A Study on the Gaseous Nitrocarburising of Cast Irons (주철의 가스질화침탄처리)

  • Kim, Y.H.;Yoon, H.J.
    • Journal of the Korean Society for Heat Treatment
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    • v.16 no.2
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    • pp.71-77
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    • 2003
  • We investigate the phase formation in the compound layer of cast irons during the gaseous nitrocarburising of four different cast irons, that contain different types of graphites in the shape and size. We examine the change in the surface roughness with the nitrocarburising time. The observation of cross-sectional microstructure and X-ray diffraction analysis indicate that the compound layer consists of single ${\varepsilon}-Fe_{2-3}(N,C)$ phase and that its thickness increases in a parabolic manner with the treatment time. The surface roughness parameters, Rz and Ra increase with increasing treatment time. In other words, the roughness parameters increase as the thickness of compound layer increases. The parameters also depend on the shape and size of graphite in the individual cast irons.

Improvement of the Wear Resistance and Anti-Corrosion of the Trivalent Cr Platings Using Heat Treatments (열처리를 통한 3가 크롬도금층의 마모 및 부식특성 개선)

  • Nam, K.S.;Park, Y.M.;Rha, J.J.;Kwon, S.C.
    • Journal of the Korean Society for Heat Treatment
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    • v.16 no.6
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    • pp.335-340
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    • 2003
  • To improve properties of wear resistance and anti-corrosion of the trivalent chromium platings, oxinitrocarbunsing and steam oxidation were conducted. Armophous trivalent Cr platings could be transformed to chromium carbides of high hardness, that showed low friction and wear rate. Even though micro-cracks were within as platings, superior anti-corrosion property was obtained by these treatments due to healing of cracks at the interface between the trivalent chromium platings and substrate.