Development of a Damage Tolerant Microstructure for Inconel 718 Turbine Disk Material

Koul, A. K.; Au, P.; Bellinger, Nicholas C.; Thamburaj, Robinson; Wallace, W.E.; Immarigeon, J.‐P.

doi:10.7449/1988/superalloys_1988_3_12

Cited by 41 publications

(27 citation statements)

References 6 publications

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“…This occurs during homogenization and HIP treatments due to Nb-rich ′′ dissolution, as mentioned earlier. However, as relative amounts of ′′ decrease during HIP treatment, carbide formation slows and the phase begins to dissolve through Ostwald ripening [34]. Specimens that undergo hot isostatic pressing after homogenization contain the γ matrix phase, as well as larger MC-carbide and δ phase precipitates labeled 1, 2, and 3 in Figure 7a, respectively.…”

Section: Microstructural Development Of Heat Treated Inconel 718mentioning

confidence: 99%

“…The ′′ and δ phases dissolve at temperatures above 1032 °C [34]. Dissolution of ′′ stimulates the growth of MC-carbides during HIP treatment [13].…”

Section: Microstructural Development Of Heat Treated Inconel 718mentioning

confidence: 99%

“…Carbides with the composition NbC were reported in homogenized and HIPed SLM IN718 printed horizontally with respect to the building direction [13]. NbC carbides have a solvus temperature between 1040-1093 °C [34]. Rao et al [35] observed Nb-and Ti-rich MC-carbides along grain boundaries in powder compaction-sintering specimens of IN718 fabricated by HIP (1200 °C at 120 MPa for 3 h), a subsequent heat treatment (955 °C for one hour, then quenched), and double aging (720 °C for 8 h and furnace cooled followed by 620 °C for 8 h, then air cooled).…”

Section: Microstructural Development Of Heat Treated Inconel 718mentioning

confidence: 99%

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Microstructural and Microhardness Evolution from Homogenization and Hot Isostatic Pressing on Selective Laser Melted Inconel 718: Structure, Texture, and Phases

Seede

Mostafa

Braïlovski

et al. 2018

JMMP

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Abstract:In this work, the microstructure, texture, phases, and microhardness of 45 • printed (with respect to the build direction) homogenized, and hot isostatically pressed (HIP) cylindrical IN718 specimens are investigated. Phase morphology, grain size, microhardness, and crystallographic texture at the bottom of each specimen differ from those of the top due to changes in cooling rate. High cooling rates during the printing process generated a columnar grain structure parallel to the building direction in the as-printed condition with a texture transition from (001) orientation at the bottom of the specimen to (111) orientation towards the specimen top based on EBSD analysis. A mixed columnar and equiaxed grain structure associated with about a 15% reduction in texture is achieved after homogenization treatment. HIP treatment caused significant grain coarsening, and engendered equiaxed grains with an average diameter of 154.8 µm. These treatments promoted the growth of δ-phase (Ni 3 Nb) and MC-type brittle (Ti, Nb)C carbides at grain boundaries. Laves phase (Fe 2 Nb) was also observed in the as-printed and homogenized specimens. Ostwald ripening of (Ti, Nb)C carbides caused excessive grain growth at the bottom of the HIPed IN718 specimens, while smaller grains were observed at their top. Microhardness in the as-fabricated specimens was 236.9 HV and increased in the homogenized specimens by 19.3% to 282.6 HV due to more even distribution of secondary precipitates, and the nucleation of smaller grains. A 36.1% reduction in microhardness to 180.5 HV was found in the HIPed condition due to γ phase dissolution and differences in grain morphology.

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Section: Microstructural Development Of Heat Treated Inconel 718mentioning

confidence: 99%

“…The ′′ and δ phases dissolve at temperatures above 1032 °C [34]. Dissolution of ′′ stimulates the growth of MC-carbides during HIP treatment [13].…”

Section: Microstructural Development Of Heat Treated Inconel 718mentioning

confidence: 99%

Section: Microstructural Development Of Heat Treated Inconel 718mentioning

confidence: 99%

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Microstructural and Microhardness Evolution from Homogenization and Hot Isostatic Pressing on Selective Laser Melted Inconel 718: Structure, Texture, and Phases

Seede

Mostafa

Braïlovski

et al. 2018

JMMP

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“…As a result, a microstructural design philosophy has been successfully developed that is aimed at improving the damage tolerance of conventional disc materials. 3 Damage tolerance, by definition, is the ability of the disc material to exhibit greater resistance to the growth of inherent or service induced flaws under creep and/or fatigue loading conditions, while still maintaming adequate low cycle fatigue pro erties, tensile strength, as well as stress rupture strength. !…”

Section: Introductionmentioning

confidence: 99%

Development and Characterization of a Damage Tolerant Microstructure for a Nickel Base Turbine Disc Alloy

Kearsey¹,

Koul²,

Beddoes³

et al. 2000

Superalloys 2000 (Ninth International Symposium)

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A modified heat treatment has been developed for the nickel-base superalloy, PWA 1113, to create a damage tolerant microstructure @TM) using mechanistic microstructural design concepts. The DTM was designed with the aim of imparting improved fatigue crack growth resistance without forfeiture of other vital properties such as tensile strength, stress rupture life, and low cycle fatigue lifetimes. This was achieved by optimizing the material's grain size, grain boundary morphology, and the intragranular precipitate size and distribution. Mechanical testing demonstrated that when compared to the conventional microstructure (CM), the short crack growth rate for the DTM was slower by a factor of 3 at room temperature, and 2.2 times slower at 482 "C. Creep test results showed that at 690 MPa (100 ksi) and 705 "C, the creep-rupture life was extended by a factor of almost 4 for the new DTM. Tensile test results indicated minimal strength losses for the DTM with respective YS and UTS values of 80% and 90% of the CM baseline values at both test temperatures.

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“…But, it was reported that δ-phase of globular morphology was promising for fatigue properties [19][20]. A lot of studies were performed about heat treatment for enhancement of mechanical properties, however, many problems are still remaining about δ/γ″/γ′-phase control, grain size and precipitation free zone(PFZ) [21,22].…”

Section: Introductionmentioning

confidence: 99%

Effects of Cyclic Solution Treatment on the Microstructures and Mechanical Properties of Alloy 718

Hong¹,

Park²,

Park³

et al. 2005

Superalloys 718, 625, 706 and Various Derivatives (2005)

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Effects of solution treatment on the microstructure and mechanical properties in wrought Alloy 718 were investigated. For the improvement of tensile and fatigue properties of wrought Alloy 718, a cyclic solution treatment, heating at 1000 for 3 minutes followed by furnace cooling at the rate of 3 /minute and holding at 985 for 8 minutes, was proposed. The cyclic treatment was performed repeatedly 3 times and the samples were air-cooled to room temperature. After the cyclic solution heat treatment, Alloy 718 was subject to the standard aging treatment, holding at 718 for 8 hours followed by cooling at the rate of 55 /hour and holding at 620 for 8 hours, and finally air cooled to room temperature. For the purpose of comparison, a standard heat treatment was also performed by solution treatment at 955 followed by aging. The microstructures of the heat-treated samples were analyzed by optical microscopy and scanning electron microscope (SEM). Cyclic solution treatment resulted in the formation of small spherical shaped δ-phases without grain growth. However, the δ-phases of the standard heattreated specimen showed needle-like morphologies. Tensile and low cycle fatigue tests were performed on both cyclic heat-treated and standard heat-treated specimens at room temperature, 350 and 650 . Low cycle fatigue tests on the cyclic treated specimens showed promising results without reduction of strength.

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Development of a Damage Tolerant Microstructure for Inconel 718 Turbine Disk Material

Abstract: A new modified heat treatment has been developed for Inconel 718.

Cited by 41 publications

References 6 publications

Microstructural and Microhardness Evolution from Homogenization and Hot Isostatic Pressing on Selective Laser Melted Inconel 718: Structure, Texture, and Phases

Microstructural and Microhardness Evolution from Homogenization and Hot Isostatic Pressing on Selective Laser Melted Inconel 718: Structure, Texture, and Phases

Development and Characterization of a Damage Tolerant Microstructure for a Nickel Base Turbine Disc Alloy

Effects of Cyclic Solution Treatment on the Microstructures and Mechanical Properties of Alloy 718

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