• Title/Summary/Keyword: Fe-base superalloy

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A Study on Hot Cracking in Ni-Base Superalloy Welds (I) - Effect of Fe Contents on Solidification Cracking Susceptibility in Weld Metal - (Ni기 초내열합금 용접부의 고온균열에 관한 연구(I) - 용접금속의 응고균열 감수성에 미치는 Fe의 영향 -)

  • ;;Kazutoshi Nishimoto
    • Journal of Welding and Joining
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    • v.19 no.6
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    • pp.614-621
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    • 2001
  • A study was carried out to determine the solidification cracking susceptibility of Ni-base superalloy as a function of Fe content in base metal. Three kinds of Ni-base superalloys with three different levels of Fe content were used. The solidification cracking susceptibility was evaluated by the Trans-Varestraint test at four different strain levels. Quantitative analysis of crack revealed that the solidification crack length and the temperature range in which hot cracking occurred in fusion zone (Brittle Temperature Range, BTR) decreased with a decrease in Fe content. Further, the thermo-calc data indicated that the solidification temperature range also decreased with decreasing Fe content. From these results, it was deduced that the improvement of the solidification cracking susceptibility with decreasing Fe content was attributed to the decrease of the solidification temperature range.

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Synthesis and Microstructure of Fe-Base Superalloy Powders with Y-Oxide Dispersion by High Energy Ball Milling (고에너지 볼 밀링을 이용한 Y-산화물 분산 Fe-기초내열합금 분말의 합성 및 미세조직 특성)

  • Yim, Da-Mi;Park, Jong Kwan;Oh, Sung-Tag
    • Korean Journal of Materials Research
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    • v.25 no.8
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    • pp.386-390
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    • 2015
  • Fe-base superalloy powders with $Y_2O_3$ dispersion were prepared by high energy ball milling, followed by spark plasma sintering for consolidation. High-purity elemental powders with different Fe powder sizes of 24 and 50 mm were used for the preparation of $Fe-20Cr-4.5Al-0.5Ti-O.5Y_2O_3$ powder mixtures (wt%). The milling process of the powders was carried out in a horizontal rotary ball mill using a stainless steel vial and balls. The milling times of 1 to 5 h by constant operation (350 rpm, ball-to-powder ratio of 30:1 in weight) or cycle operation (1300 rpm for 4 min and 900 rpm for 1 min, 15:1) were applied. Microstructural observation revealed that the crystalline size of Fe decreased with an increase in milling time by cyclic operation and was about 15 nm after 3 h, forming a FeCr alloy phase. The cyclic operation had an advantage over constant milling in that a smaller-agglomerated structure was obtained. The milled powders were sintered at $1100^{\circ}C$ for 30 min in vacuum. With an increase in milling time, the sintered specimen showed a more homogeneous microstructure. In addition, a homogenous distribution of Y-compound particles in the grain boundary was confirmed by EDX analysis.

Effect of Powder Synthesis Method on the Microstructure of Oxide Dispersion Strengthened Fe-Cr-Al Based Alloys (Fe-Cr-Al 기 산화물 분산강화 합금의 미세조직에 미치는 분말제조 공정 영향)

  • Park, Sung Hyun;Oh, Sung-Tag
    • Korean Journal of Materials Research
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    • v.27 no.9
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    • pp.507-511
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    • 2017
  • An optimum route to fabricate oxide dispersion strengthened ferritic superalloy with desired microstructure was investigated. Two methods of high energy ball milling or polymeric additive solution route for developing a uniform dispersion of $Y_2O_3$ particles in Fe-Cr-Al-Ti alloy powders were compared on the basis of the resulting microstructures. Microstructural observation revealed that the crystalline size of Fe decreased with increases in milling time, to values of about 15-20 nm, and that an FeCr alloy phase was formed. SEM and TEM analyses of the alloy powders fabricated by solution route using yttrium nitrate and polyvinyl alcohol showed that the nano-sized Y-oxide particles were well distributed in the Fe based alloy powders. The prepared powders were sintered at 1000 and $1100^{\circ}C$ for 30 min in vacuum. The sintered specimen with heat treatment before spark plasma sintering at $1100^{\circ}C$ showed a more homogeneous microstructure. In the case of sintering at $1100^{\circ}C$, the alloys exhibited densified microstructure and the formation of large reaction phases due to oxidation of Al.

Heat Treatment of Superalloys for High Temperature Applications (고온구조용 초내열합금 열처리)

  • Park, Nho-Kwang
    • Journal of the Korean Society for Heat Treatment
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    • v.16 no.6
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    • pp.341-348
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    • 2003
  • Superalloys which can be devided into three categohes, i.e. Ni-base, Co-base, and Fe-base alloys are widely used for high temperature applications. Since superalloys contain many alloying elements and precipitates, its chemistry and processing parameters need to be carefully designed. In this review, current state-of-the art in the superalloy technologies is described with special attention to the heat-treatment for the control of the microstructures and mechanical properties.

Determination of Material Parameters for Microstructure Prediction Model Based on Recystallization and Grain Growth Behaviors (재결정 및 결정립 성장거동을 기초한 조직예측 모델에 대한 변수 결정방법)

  • Yeom, J.T.;Kim, J.H.;Hong, J.K.;Park, N.K.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2009.05a
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    • pp.270-273
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    • 2009
  • This work describes a method of determining material parameters included in recrystallization and grain growth models. Focus is on the recrystallization and grain growth models of Ni-Fe base superalloy, Alloy 718. High temperature compression tests at different strain, strain rate and temperature conditions were chosen to determine the material parameters of dynamic recrystallization model. The critical strain and dynamically recrystallized grain size and fraction at various process variables were quantitated with the microstructual analysis and strain-stress relationships of the compression tests. Besides, isothermal heat treatments were utilized to fit the material constants included in the grain growth model. Verification of the determined material parameters is carried out by comparing the measured data obtained from other compression tests.

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The effects of overlapping ratio on surface properties in laser cladding (레이저 클래딩 중첩도가 표면특성에 미치는 영향)

  • 이제훈;서무홍;한유희
    • Laser Solutions
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    • v.3 no.1
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    • pp.38-45
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    • 2000
  • A 4㎾ RS840 CO2 laser with a powder auto-feeding apparatus has been used to deposit multiple overlapping tracks of Ni-base superalloy on to low carbon steel. It was found that the surface roughness(turbulence) of an overlapped cladding layer decreased with the increase of the overlapping ratio in an oscillating manner. When the overlapping ratio had values of 0.62, the surface turbulence was lowest. Overlapping ratio offer significant potential for improvement of materials surface properties such as corrosion performance and wear resistance. This paper reports that the overlapping ratio shows best corrosion resistance. The tensile residual stresses generated at the higher overlapping ratio( > 0.45) and the element concentration of Fe increased in the surface layer at the lower overlapping ratio( < 0.45) may lead to worse corrosion resistance.

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Corrosion Behavior and Effect of Alloying Elements of Fe-base and Ni-base Superalloys on Hot Molten Salt (고온 용융염에서 Fe기 및 Ni기 초합금의 부식거동 및 합금원소의 영향)

  • Jo, Su-Haeng;Jang, Jun-Seon;Jeong, Myeong-Su;O, Seung-Cheol;Sin, Yeong-Jun
    • Korean Journal of Materials Research
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    • v.9 no.10
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    • pp.985-991
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    • 1999
  • Corrosion behaviors of Incoloy 800H, KSA(Kaeri Superalloy)-6, Inconel 600 and Hastelloy C-276 in molten salts were investigated in the temperature range of 650 ~ $850^{\circ}C$. Due to $\textrm{Li}_{2}\textrm{O}$-induced basic fluxing mechanism, the corrosion rates of the alloys in mixed molten salt of LiC1-$\textrm{Li}_{2}\textrm{O}$ were significantly higher than those in molten salt of LiCl. In the mixed molten salt, Fe-base alloys showed higher corrosion resistance than the Ni-base alloys. and Hastelloy C-276 with high Mo and W contents exhibited the highest corrosion rate among the examined alloys. The single layer of $\textrm{LiCrO}_{2}$ was formed in molten salt of LiCl and two phase structure of a scale consisted of oxides and Ni was formed in the mixed molten salt.

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Microstructural Evaluation and High Temperature Mechanical Properties of Ni-22Cr-18Fe-9Mo ODS Alloy (Ni-22Cr-18Fe-9Mo계 ODS 합금의 미세조직 및 고온인장 특성 평가)

  • Jeong, Seok-Hoan;Kang, Suk-Hoon;Han, Chang-Hee;Kim, Tae-Kyu;Kim, Do-Hyang;Jang, Jin-Sung
    • Journal of Powder Materials
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    • v.18 no.5
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    • pp.456-462
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    • 2011
  • Yttrium oxide is one of the most thermo-dynamically stable materials, so that it is generally used as a dispersoid in many kinds of dispersion strengthed alloys. In this study, a nickel-base superalloy is strengthened by dispersion of yttrium oxide particles. Elemental powders with the composition of Ni-22Cr-18Fe-9Mo were mechanically alloyed(M.A.) with 0.6 wt% $Y_2O_3$. The MA powders were then HIP(hot isotactic press)ed and hot rolled. Most oxide particles in Ni-22Cr-18Fe-9Mo base ODS alloy were found to be Y-Ti-O type. The oxide particles were uniformly dispersed in the matrix and also on the grain boundaries. Tensile test results show that the yield strength and ultimate tensile strength of ODS alloy specimens were 1.2~1.7 times higher than those of the conventional $Hastelloy^{TM}$ X(R), which has the same chemical compositions with ODS alloy specimens except the oxide particles.

Can design for Blisk of Nickel-base Superalloy Powder (분말합금을 이용한 블리스크 제조용 캔 설계)

  • Lim J. S.;Yeom J. T.;Kwon Y. S.;Park N. K.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2004.10a
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    • pp.171-174
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    • 2004
  • Superalloys with many strengthening alloying elements are frequently used in powder form to alleviate harmful effects of alloy segregation. HIP (hot isostatic pressing) and DB (diffusion bonding) as a form of solid-state bonding process is often used to make turbine components, such as integrated turbine rotors. HIP/DB process requires many technical overcomes related to dimensional changes as well as microstructural control. In this research, HIP/DB process for nickel base superalloys, Udimet 720, were investigated with a view to control the dimensional change during the consolidation process. Simple disc-shaped cans were used to select the conceptual die design for the control of the dimensional change especially in radial direction. The change in the shape of consolidated shape was investigated using commercial FE code with constitutive equations for low temperature plasticity and creep deformation.

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Microstructure and Creep Fracture Characteristics of Dissimilar SMA Welds between Inconel 740H Ni-Based Superalloy and TP316H Austenitic Stainless Steel (Inconel 740H 니켈기 초내열합금과 TP316H 스테인리스강의 이종금속 SMA 용접부의 미세조직과 크리프 파단 특성)

  • Shin, Kyeong-Yong;Lee, Ji-Won;Han, Jung-Min;Lee, Kyong-Woon;Kong, Byeong-Ook;Hong, Hyun-Uk
    • Journal of Welding and Joining
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    • v.34 no.5
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    • pp.33-40
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    • 2016
  • The microstructures and the creep rupture properties of dissimilar welds between the Ni-based superalloy Inconel 740H and the non-stabilized austenitic stainless steel TP316H have been characterized. The welds were produced by shielded metal arc (SMA) welding process with the AWS A5.11 Class ENiCrFe-3 filler metal, commonly known as Inconel 182 superalloy. Postweld heat treatment at $760^{\circ}C$ for 4 hours was conducted to form ${\gamma}^{\prime}$ strengthener in Inconel 740H. The austenitic weld metal produced by Inconel 182 had a dendritic microstructure, and grew epitaxially from the both sides of Inconel 740H and TP316H base metals. Since both Inconel 740H and TP316H did not undergo any solid-state transformation during welding process, there were no heat-affected-zone (HAZ) sub-regions and the coarsoned grains near the weld interface were limited to a narrow region. The hardness of Inconel 182 weld metal was ~220 Hv. The gradual hardness decrease was detected at HAZ of TP316H, and the TP316H base metal displayed the lowest hardness value (~180 Hv) whilst the Inconel 740H showed the highest hardness value (~400 Hv). Fracture after creep occurred at the center of weld metal, regardless of creep condition. It was found that during creep the cracks initiated and propagated along interdendritic regions and grain boundaries at which Laves particles enriched in Nb, Si and Cr were present. The appropriate design of weld metal was discussed to suppress the creep-induced cracking of the present dissimilar weld.