Alloy 706 Metallurgy and Turbine Wheel Application

Schilke, P. W.; Pepe, Joseph; Schwant, R.C.

doi:10.7449/1994/superalloys_1994_1_12

Cited by 50 publications

(27 citation statements)

References 8 publications

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“…This excellent balance of chemical composition results in superior characteristics to Alloy 718 in the segregation tendency, hot workability and machinability (2)(3)(4). Therefore, Alloy 706 is suitable for large forgings and has been used for high temperature services (5).…”

Section: Introductionmentioning

confidence: 99%

Effects of Aluminum, Titanium and NioBium on the Time-Temperature-Precipitation Behavior of Alloy 706

Shibata¹,

Shudo²,

Yoshino³

1996

Superalloys 1996 (Eighth International Symposium)

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Ni-Fe-base superalloy 706 has been used for high temperature services.The time -temperature -precipitation (TTP) diagram is essential in the design of heat treatments for any precipitation strengthened superalloy.The TTP diagrams have been already presented for Alloy 706. However, effects of aluminum, titanium and niobium, important substitutional elements of y ' and y " precipitates, on the TTP behavior are not clear in the literature.In this study, the TTP and the time -temperature -hardness (TTH) diagrams are presented for experimental alloys containing only one or two of Ti, Nb and Al, in a temperature range of 600 -900°C. The observation by optical microscopy, scanning electron microscopy and transmission electron microscopy revealed that y ' , y ", y '-y " co-precipitates and 17 form in alloys containing Ti.Among the three elements, Ti plays the most important role in the precipitation strengthening behavior of Alloy 706. Furthermore, neither Al nor Nb can demonstrate their effects without Ti addition. Nb promotes y " formation and prevents 7 formation. Al enhances the formation of stable y '-y " co-precipitates, more effectively in the co-existence of Ti and Nb.

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Section: Introductionmentioning

confidence: 99%

Effects of Aluminum, Titanium and NioBium on the Time-Temperature-Precipitation Behavior of Alloy 706

Shibata¹,

Shudo²,

Yoshino³

1996

Superalloys 1996 (Eighth International Symposium)

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“…This excellent balance of these allloying elements results in superior characteristics to Alloy 718 in segregation tendency, hot workability and machinability (2)(3)(4). Therefore, Alloy 706 is suitable for large forgings and has been used for high temperature services (5).…”

Section: Introductionmentioning

confidence: 99%

Effect of Cooling Rate from Solution Treatment on Precipitation Behavior and Mechanical Properties of Alloy 706

Shibata¹,

Takahashi²,

Shudo³

et al. 1997

Superalloys 718, 625, 706 and Various Derivatives (1997)

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The time -temperature -precipitation behavior of N&Fe-base superalloy 706 is very complicated because many kinds of precipitates exist in this alloy. Therefore, TTP behavior of this alloy vary with the heat treatment program and condition, and so do mechanical properties accordingly. In this study, TTP and TTH diagrams on cooling from the solution treatment of three experimental alloys and Alloy 706 are presented in a temperature range from 600 to 900°C for up to 100h. The observations by optical microscopy, scanning electron microscopy and transmission electron microscopy revealed that y ', y ", double cuboidal y '-y " co-precipitate (compact morphology), overlaid y '-y " co-precipitate (non-compact morphology) and 7 appeared in this alloy despite that the double cuboidal co-precipitate does not exist in the usual TTP diagram which is composed on re-heating from room temperature after the solution treatment.The dependence of microstructure and mechanical properties of aged Alloy 706 on the cooling rate after the solution treatment was also examined. The solution treatment was conducted at 980°C for 3h, and the cooling rate was varied from 0.5 to 8.5 "C/min. Tensile strength and 0.2% yield strength were maximized at 35 "C/min, while elongation and reduction of area suddenly decreased below 3-5 "C/min. Creep rupture life was also maximized at 3-5 "C/min, but creep rupture ductility suddenly increased below 3-5 "C/min. These changes can be explained in terms of the precipitation behavior such as the formation of 7 at grain boundaries and the double cuboidal y '-y " co-precipitate inside grains in the case of low cooling rate.

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“…This is most pronounced for nitrogen atomized P/M 706 with the larger number of carbonitrides. Annealing studies of hot forged P/M 706 indicate higher resistance to grain growth in this material as compared to C/w 706 [6]: P/M 706 has rive to eight times mailer grains than C/W 706 [6] after the same high temperature exposure ( Figure 5). This corresponds to ASTM No.…”

Section: Introductionmentioning

confidence: 91%

“…This way of processing reduces, but may not totally avoid melt-related defects and segregation, especially in very large parts. Also, C/W 706 is prone to grain growth and therefore requires low forging temperatures which necessitates very large pressing forces [6].…”

Section: Introductionmentioning

confidence: 99%

First and Second Tier Properties of HIP and Forged P/M 706

Habel¹,

Rizzo²,

Conway³

et al. 1997

Superalloys 718, 625, 706 and Various Derivatives (1997)

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Powder metallurgical (P/M) versions of Inconel@ 706, an iron/nickel-base superalloy, were evaluated*. The materials were gas atomized, consolidated by hot isostatic pressing (HIP) and subsequently forged to small pancakes. Effects of powder metallurgical processing parameters were investigated such as atomization gas, powder particle size fraction and HIP temperature. P/M 706 has a finer microstructure and a higher resistance to grain growth than conventionally cast and wrought (C/W) 706. High temperature hot compression testing shows about 10% lower flow stress for P/M 706 than for C/W 706. Tensile properties of as-HIP and solution treated and aged P/M 706 compare favorably to forged, solutionized and aged C/W 706, while Charpy impact strength is lower. Due to overaging in this study, HIP, forged, solution treated and aged PM 706 has a lower strength than usually observed in forged, solution treated and aged C/W 706. Low cycle fatigue results are excellent and exceed C/W 706 values by factors of 3 to 5. The fine and homogeneous grain size and the absence of any significant segregation observed in the P/M 706 is expected to greatly facilitate forging of large turbine disk shapes.

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Alloy 706 Metallurgy and Turbine Wheel Application

Cited by 50 publications

References 8 publications

Effects of Aluminum, Titanium and NioBium on the Time-Temperature-Precipitation Behavior of Alloy 706

Effects of Aluminum, Titanium and NioBium on the Time-Temperature-Precipitation Behavior of Alloy 706

Effect of Cooling Rate from Solution Treatment on Precipitation Behavior and Mechanical Properties of Alloy 706

First and Second Tier Properties of HIP and Forged P/M 706

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