• Title/Summary/Keyword: Treatment Phase

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Effect of Vacuum Heat Treatment on the Properties in Thermal Sprayed Ceramics Coating (세라믹스 용사 코팅 특성에 미치는 진공열처리의 영향)

  • Lee, J.I.;Ur, S.C.;Lee, Y.G.
    • Journal of the Korean Society for Heat Treatment
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    • v.13 no.2
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    • pp.98-102
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    • 2000
  • The effect of vacuum heat treatment in the thermal sprayed ceramics coating on a capstan by either high velocity oxygen fuel(HVOF) or plasma thermal spray process was investigated. The coating materials applied on the capstan were tungsten and chrome carbides. In order to characterize the interface between coating layer and bare materials, hardness, adhesion strength, X-ray diffraction(XRD) and microstructural analysis are conducted. The adhesion strength of the carbide coated materials by HVOF process is over 500MPa compared to those of plasma coating process is 230MPa. In case of the carbide coated materials by HVOF process, the adhesion strength is increased to 15MPa and the porosity is reduced under 5% by vacuum heat treatment for 5 hrs at $1000^{\circ}C$. The XRD results reveal that the increasement is believed due to the phase stabilization of metastable $Cr_3C_2$ phase to stable $Cr_{23}C_6$ phase.

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Effect of Heat Treatment on the Microstructural Evolution of Pt-aluminide Coated Ni-based Superalloy (Pt-Aluminide로 코팅된 초내열합금의 열처리에 따른 미세조직변화)

  • Joo, D.;Park, S.H.;Jung, Y.G.;Lee, K.H.;Kim, C.S.
    • Journal of the Korean Society for Heat Treatment
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    • v.19 no.2
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    • pp.103-108
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    • 2006
  • Microstructural evolution of Pt-aluminide coated Ni-based superalloy has been investigated with ductilization heat treatment. The Pt coat was prepared on the superalloy and then aluminide coating was conducted using a pack cementation process. Samples were heat-treated at $1050^{\circ}C$ for 2 hrs and the microstructure and element analysis were preformed. A various precipitated compounds were observed within the coating layer and the diffusion region in the Pt-aluminide coating and heat treatment, indicating that the bi-phase compounds of $PtAl_2$ and NiAl were performed during the Pt-aluminide coating, whereas $M_{23}C_6$, MC, $Ni_3Al$ and ${\sigma}$ phases were precipitated in the inter-diffusion region. The bi-phase compounds of $PtAl_2$ and NiAl were transformed into the single phase compound of $PtAl_2$ with the heat treatment, increasing the amount of carbide and ${\sigma}$ phase.

Effect of Phase Transformation Behavior of Electroless Nickel Plating Layer on Corrosion and Cavitation-Erosion with Heat Treatment (열처리에 따른 무전해 니켈 도금 층의 상변태 거동이 부식과 캐비테이션 침식에 미치는 영향)

  • Il-Cho Park;Seong-Jong Kim
    • Corrosion Science and Technology
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    • v.23 no.1
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    • pp.64-71
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    • 2024
  • The objective of this study was to investigate corrosion and cavitation-erosion characteristics of the electroless nickel plating layer with heat treatment. The crystallization temperature of the electroless nickel plating layer was about 410 ℃. The phase transformation energy was confirmed to be 12.66 J/g. With increasing heat treatment temperature, the amorphous electroless nickel plating layer gradually changed to crystalline Ni and Ni3P. At the same time, the crystal grain size was also increased. Additionally, when heat treatment was performed at a temperature above 400 ℃, NiO phase was observed due to oxidation phenomenon. As a result of the electrochemical polarization experiment, the corrosion resistance of the heat-treated electroless nickel plating layers was superior to that of the as-deposited plating layer. This was because crystal grains became larger and grain boundaries decreased during heat treatment. The cavitation-erosion resistance of heat-treated plating layers tended to be superior to that of as-deposited plating layers due to increased microhardness.

Effect of Crystallization of Matrix Phase on the Fracture Toughness of Silicon Nitride Ceramics (질화규소 요업체의 기지상 결정화가 파괴인성에 미치는 영향)

  • 김남균;김도연;강대갑
    • Journal of the Korean Ceramic Society
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    • v.24 no.4
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    • pp.364-368
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    • 1987
  • The Si5AION7 specimens containing 20% YAG composition have been sintered and then heat treated to induce the crystallization of the matrix glassy phase. Crystallization of YAG phase during the heat treatment was detected from the X-ray diffraction patterns and the consequent changes in room temperature toughness as well as in microstructures were investigated. Almost all the glassy boundary phase were found to crystallize even after 5 minutes of heat treatment and the KC at room temperature decreased accordingly. The results show that the matrix crystallization can be induced by slow cooling from the sintering temperature.

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Nitrogen Permeation Treatment of Duplex and Austenitic Stainless Steels

  • Yoo, D.K.;Joo, D.W.;Kim, Insoo;Kang, C.Y.;Sung, J.H.
    • Journal of the Korean Society for Heat Treatment
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    • v.15 no.2
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    • pp.57-64
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    • 2002
  • The 22%Cr-5%Ni-3%Mo duplex and 18%Cr-8%Ni austenitic stainless steels have been nitrogen permeated under the $1Kg/cm^2$ nitrogen gas atmosphere at the temperature range of $1050^{\circ}C{\sim}1150^{\circ}C$. The nitrogen-permeated duplex and austenitic stainless steels showed the gradual decrease in hardness with increasing depth below surface. The duplex stainless steel showed nitrogen pearlite at the outmost surface and austenite single phase in the center after nitrogen permeation treatment, while the obvious microstructural change was not observed for the nitrogen-permeated austenitic stainless steel. After solution annealing the nitrogen-permeated stainless steels(NPSA treatment) at $1200^{\circ}C$ for 10 hours, the hardness of the duplex and austenitic stainless steels was constant through the 2 mm thickness of the specimen, and the ${\alpha}+{\gamma}$ phase of duplex stainless steel changed to austenite single phase. Tensile strengths and elongations of the NPSA-treated duplex stainless steel remarkably increased compared to those of solution annealed (SA) duplex stainless steel due to the solution strengthening effect of nitrogen and the phase change from a mixture of ferrite and austenite to austenite single phase, while the NP-treated austenitic stainless steel displayed the lowest value in elongation due to inhomogeneous deformation by the hardness difference between surface and interior.

Effect of Grain Size and Heat-treating Atmosphere on the Phase Stability of Y-TZP (입자크기와 열처리 분위기 변화에 따른 Y-TZP에서의 상안정성 변화)

  • Chung, Tai-Joo;Ahn, Seung-Su;Song, Eun-Wha;Oh, Kyung-Sik;Lee, Jong-Sook;Kim, Young-Sik
    • Journal of Powder Materials
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    • v.13 no.5 s.58
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    • pp.360-365
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    • 2006
  • The phase stability of tetragonal phase in Y-TZP was investigated in terms of the distribution of grain sizes and heat-treating atmosphere. Y-TZP with various grain sizes were prepared using duration time at $1600^{\circ}C$ as experimental parameter. Accumulated grain size distributions were built from the SEM micrographs and the amount of tetragonal phase were measured using XRD. Both results were compared to determine the critical grain size before and after heat-treatment in vacuum. The critical grain size drastically decreased compared with the small increase of average grain size due to the autocatalytic effect which critically affects the tetragonal to monoclinic phase transformation. After heat-treatment in reductive atmosphere critical grain size relatively increased due to the stabilization of tetragonal phase. The formation of oxygen vacancies during heat-treatment was ascribed to the increase of stability.

Two-step Solution Treatment for Enhancement of Mechanical Properties of AlSiCu Aluminum Alloy (Al6Si2Cu 알루미늄 합금의 기계적 물성 향상을 위한 이단계 고용화 열처리)

  • Park, Sang-Gyu;Kim, Chung-Seok
    • Journal of the Korean Society for Heat Treatment
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    • v.31 no.3
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    • pp.97-103
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    • 2018
  • The objective of this study is to develop the mechanical properties of AlSiCu aluminum alloy by the two-step solution heat treatment. The microstructure of gravity casting specimen represents a typical dendrite structure having a secondary dendrite arm spacing (SDAS) of 40 mm. In addition to the Al matrix, a large amount of coarsen eutectic Si phase, $Al_2Cu$ intermetallic phase, and Fe-rich phases are generated. The eutectic Si phases are fragmented and globularized with solution heat treatment. Also, the $Al_2Cu$ intermetallic phase is resolutionized into the Al matrix. The $2^{nd}$ solution temperature at $525^{\circ}C$ might be a optimum condition for enhancement of mechanical properties of AlSiCu aluminum alloy.

Phase transformation of $REBa_2Cu_3O_{7-x}$ (RE=Nd, Gd, Dy) Superconductor during Continuous Cooling and Isothermal Heat Treatment (등온열처리와 냉각에 따른 $REBa_2Cu_3O_{7-x}$ (RE=Nd, Gd, Dy) 초전도체의 상변화)

  • O, Yong-Taek;Shin, Dong-Chan;Han, Young-Hee;Sung, Tae-Hyun;Jeong, Nyeon-Ho
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.05a
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    • pp.42-45
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    • 2003
  • The phase transformation of $REBa_2Cu_3O_{7-x}$ (RE=Nd, Gd, Dy) was investigated using isothermal heat-treatment and continuous cooling in air. During continuous cooling, the $REBa_2Cu_3O_{7-x}$ (RE=123) superconducting phase with well-distributed $REBa_2Cu_3O_{7-x}$ (RE-211) was obtainde at a cooling rate of $0.001^{\circ}C$/s. Single phase RE-123 (Nd, Gd, Dy) was stable at $1050^{\circ}C$, $1050^{\circ}C$, and $950^{\circ}C$ during isothermal heat-treatment, respectively. Above these temperatures the RE-211 phase existed within the RE-123 grains. The RE-123, RE-211, $BaCu_2Od_2$, and CuO phases coexisted at $50^{\circ}C$ below the partial melting temperature for each respective rare-earth RE-123.

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Effects of Heat Treatment Temperature and Cooling Method on Microstructure and Hardness of Cu-22Sn alloy (열처리 온도 및 냉각방법이 Cu-22Sn합금의 미세조직 및 경도변화에 미치는 영향)

  • Jeong, Museob;Shin, Ari;Han, Jun Hyun
    • Journal of the Korean Society for Heat Treatment
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    • v.31 no.3
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    • pp.104-110
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    • 2018
  • The effects of heat treatment time and cooling method on microstructure and mechanical property of Cu-22wt%Sn alloy were discussed. ${\alpha}+{\delta}$ mixed phase structure was obtained in air-cooled specimens after heat treatment at 775, 750, and $700^{\circ}C$ for 1 hour. On the other hand, in water-cooled specimens, ${\alpha}+{\beta}^{\prime}$ martensite mixed phase was obtained. In the case of water-cooled specimens, the hardness value decreased with decreasing heat treatment temperature because the volume fraction of ${\alpha}$ phase with low hardness value increased as the heat treatment temperature decreased. In water-cooled specimen after heat treatment at $600^{\circ}C$, ${\gamma}^{\prime}$ martensite was formed instead of ${\beta}^{\prime}$ martensite. The hardness value of ${\gamma}^{\prime}$ martensite was lower than those of ${\beta}^{\prime}$ and ${\delta}$ phases.

Effect of Hot-stamping Heat Treatment on the Microstructure of Al-Segregated Zone in TWB Laser Joints of Al-Si-coated Boron Steel and Zn-coated DP Steel (Al-Si 도금된 보론강과 Zn 도금된 DP강 TWB 레이저 용접부내의 Al-편석부 미세조직에 미치는 핫스탬핑 열처리의 영향)

  • Jung, Byung Hun;Kong, Jong Pan;Kang, Chung Yun
    • Korean Journal of Metals and Materials
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    • v.50 no.6
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    • pp.455-462
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    • 2012
  • Al-Si coated boron steel and Zn coated DP steel plates were laser-welded to manufacture a Tailor Welded Blank (TWB) for a car body frame. Hot-stamping heat treatment ($900^{\circ}C$, 5 min) was applied to the TWB weld, and the microstructural change and transformation mechanism were investigated in the Al-rich area near the bond line of the Al-Si coated steel side. There was Al-rich area with a single phase, $Fe_3(Al,Si)$, which was transformed to ${\alpha}-Fe$ (Ferrite) after the heat treatment. It could be explained that the $Fe_3(Al,Si)$ phase was transformed to ${\alpha}-Fe$ during heat treatment at $900^{\circ}C$ for 5 min and the resultant ${\alpha}-Fe$ phase was not transformed by rapid cooling. Before the heat treatment, the microstructures around the $Fe_3(Al,Si)$ phase consisted of martensite, bainite and ${\alpha}-Fe$ while they were transformed to martensite and ${\delta}-Fe$ after the heat treatment. Due to the heat treatment, Al was diffused to the $Fe_3(Al,Si)$ and this resulted in an increase of Al content to 0.7 wt% around the Al-rich area. If the weld was held at $900^{\circ}C$ for 5 min it was transformed to a mixture of austenite (${\gamma}$) and ${\delta}-Fe$, and only ${\gamma}$ was transformed to the martensite by water cooling while the ${\delta}-Fe$ was remained unchanged.