Effect of Heat Treatment Solution on the Size and Distribution of Gamma Prime (γ´) of Super-alloy INCONEL 738

2012 ◽  
Vol 1372 ◽  
Author(s):  
I. Guzmán ◽  
A. Garza ◽  
F. Garcia ◽  
J. Acevedo ◽  
R. Méndez
Keyword(s):  
Heat Treatment ◽  
Elevated Temperature ◽  
Elevated Temperature Strength ◽  
Gamma Prime ◽  
The Matrix ◽  
Nickel Base Superalloys ◽  
Size And Morphology ◽  
Aero Engines ◽  
Nickel Base ◽  
Nozzle Guide

ABSTRACTNickel base superalloys, which are gamma prime γ‘(Ni3Al, Ti) precipitation strengthened, is largely responsible for the elevated-temperature strength of the material and the higher resistance to creep deformation. The amount of γ’ depends on the chemical composition and temperature, heat treatment, these alloy are widely used in hot sections of aero-engines, land based turbines, stator parts, nozzle guide vanes, blades and integral wheels, due to its excellent elevated temperature strength and hot corrosion resistance. The γ‘ size decreases not only by the high temperature of heat treatment solution (1120 °C), the cooling environment and cooling rate are important parameter to decrease γ’ size to 0.65 μm. This paper presents the effect of heat treatment solution in base nickel IN 738 superalloy under service conditions, on the size and morphology of the gamma phase γ’ Ni3 (Al, Ti), main phase in the nickel base superalloys. Also shown coarse carbide and precipitates gamma prime size distributed and improve interdentritic spacing in the matrix after heat treatment solution.

Finite Element Simulation and Optimisation of Ageing Precipitation in Nickel Base Superalloys with a Low Gamma-Prime (g’) Volume Fraction

2011 ◽  
Vol 172-174 ◽  
pp. 881-886 ◽  
Author(s):  
Franck Tancret ◽  
Philippe Guillemet ◽  
Florent Fournier Dit Chabert ◽  
René Le Gall ◽  
Jean François Castagné
Keyword(s):  
Heat Treatment ◽  
Finite Element ◽  
Volume Fraction ◽  
Nucleation And Growth ◽  
Thermodynamic Quantities ◽  
Gamma Prime ◽  
The Matrix ◽  
Element Approach ◽  
Automatic Heat ◽  
Nickel Base

A finite element approach is used to simulate the precipitation of Ni3(Al,Ti) intermetallics in nickel-based superalloys containing a low volume fraction of spherical g’ precipitates, in which precipitation occurs following nucleation and growth mechanisms. Classical differential equations of nucleation and growth are implemented in the software Comsol (formerly Femlab), to compute the number of precipitates per unit volume and their mean size. Another originality of the model is the use of thermodynamic quantities coming from phase diagram computations (Thermo-Calc), like the temperature variation of the equilibrium g’ volume fraction, and the evolution of the concentration of g’ forming elements (Al, Ti) in the matrix with the volume fraction of precipitates. Once adjusted to experiment in the case of isothermal ageings, the model can be used to simulate precipitation during complex thermal histories. Finally, automatic heat treatment optimisation procedures are proposed and tested, which can reduce heat treatment times by a factor of more than five.

Electron Microscopy of Hafnium-Modified Superalloys

1971 ◽  
Vol 29 ◽  
pp. 120-121
Author(s):  
P. S. Kotval ◽  
R. W. Calder
Keyword(s):  
Electron Microscopy ◽  
Elevated Temperature ◽  
Intermediate Temperature ◽  
Elevated Temperature Strength ◽  
Carbide Phases ◽  
Nickel Base Superalloys ◽  
Nickel Base ◽  
Cast Microstructure

Cast nickel-base superalloys, used in turbine hardware, are typically composed of ~ 60 vol.% γ' phase coherently precipitated in an f.c.c. matrix, eutectic phases, and one or more carbide phases. These alloys are not heat-treatable in the sense of being able to re-solution and reprecipitate the γ' phase. Hence, the properties are governed by the as-cast microstructure which has become increasingly more complex as higher elevated-temperature strength has been required. This improvement in strength has an associated penalty in that the ambient and intermediate temperature ductility of cast superalloys is poor.Recently, it has been shown that additions of hafnium in nickel-base superalloys result in substantial improvements in ductility. The results presented here are from a study undertaken to define the role of hafnium in modifying microstructure in nickel-base alloys and the effect of this modification on properties.

The Effect of Forging Variables on the Supersolvus Heat-Treatment Response of Powder-Metallurgy Nickel-Base Superalloys

2014 ◽  
Vol 45 (13) ◽  
pp. 6231-6251 ◽  
Author(s):  
S. L. Semiatin ◽  
J. M. Shank ◽  
A. R. Shiveley ◽  
W. M. Saurber ◽  
E. F. Gaussa ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Powder Metallurgy ◽  
Treatment Response ◽  
Nickel Base Superalloys ◽  
Nickel Base

Detection of Compositional Fluctuations in High Temperature Exposed Waspaloy

2001 ◽  
Vol 699 ◽  
Author(s):  
Xiaodong Zou ◽  
Tariq Makram ◽  
Rosario A. Gerhardt
Keyword(s):  
Exposure Time ◽  
Structural Integrity ◽  
Thermal Exposure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Gamma Prime ◽  
Distribution Shape ◽  
The Matrix ◽  
Quantitative Stereology ◽  
Nickel Base

AbstractWaspaloy is a nickel base super-alloy used in aircraft engines. When this alloy is placed in service, it is subjected to long term exposure at high temperatures, which can cause the reinforcing gamma prime precipitate population to fluctuate and thus affect its structural integrity. The population fluctuates as a result of coarsening, dissolution or re-precipitation. Samples exposed to 1200° F for times ranging from 0 to 12626 hours were characterized using impedance spectroscopy, microhardness measurements, x-ray diffraction and quantitative stereology. Two important parameters were derived from the impedance measurements: (1) the imaginary admittance peak magnitude (Ymax) and (2) the associated relaxation frequency (fmax). As the distribution, shape and size of the precipitates change with exposure time, these parameters were also found to vary. In addition to the changes in precipitate geometry, lattice constant changes detected by analyzing x-ray diffraction data suggest that there are compositional shifts in the matrix as well as the gamma prime precipitates. Furthermore, the preferred orientation of the precipitates can also be seen to change with exposure time. These changes in composition, size and shape as a function of thermal exposure time are accompanied by changes in the volume fractions of primary and secondary gamma prime particles present. Using effective medium models, it is possible to predict that the measured properties are related to the gamma prime population. The grain boundary carbides do not appear to play any role at the conditions presented.

Evaluation of the Stability of Raft Structure in Nickel Base Superalloys Throughout their Lifetime

2006 ◽  
Vol 980 ◽  
Author(s):  
Katsushi Tanaka ◽  
Toru Inoue ◽  
Tetsu Ichitsubo ◽  
Kyosuke Kishida ◽  
Haruyuki Inui
Keyword(s):  
Strain Energy ◽  
Lattice Misfit ◽  
Gamma Prime ◽  
Lamellar Interface ◽  
Nickel Base Superalloys ◽  
Nickel Base ◽  
The Stability ◽  
Numerical Calculation Method ◽  
Creep Deformations ◽  
Lamellar Interfaces

AbstractStability of raft structure in nickel base superalloys has been examined by using elastic energy calculations based on a microelasticity theory. The numerical calculation method for a structurally heterogeneous system is applied. The results indicate that the raft structure is significantly stabilized by introductions of creep deformations till the critical creep deformation at which the lattice misfit between gamma and gamma-prime phases is completely compensated by creep dislocations. When the magnitude of creep deformations exceed the critical value, the (001) lamellar interfaces become elastically unstable and a tilted lamellar interface become the most stable one. This instability of the 001 raft structure leads a tilted or wavy lamellar interfaces for reducing the internal strain energy, that is a precursor to collapse the raft structure.

Long-Term Gamma Prime Phase Stability after Various Heat Treatment Conditions with Temperature Dropping during Solution Treatment in Cast Nickel Base Superalloy, Grade Inconel-738

2017 ◽  
Vol 891 ◽  
pp. 420-425
Author(s):  
Sureerat Polsilapa ◽  
Aimamorn Promboopha ◽  
Panyawat Wangyao
Keyword(s):  
Heat Treatment ◽  
Turbine Blades ◽  
Solution Treatment ◽  
Nickel Base Superalloy ◽  
Gamma Prime ◽  
Nickel Based Superalloy ◽  
Treatment Conditions ◽  
Nickel Base ◽  
Base Superalloy

Cast nickel based superalloy, Grade Inconel 738, is a material for turbine blades. Its rejuvenation heat treatment usually consist of solution treatment condition with temperature range of 1125-1205 oC for 2-6 hours. Then it is following with double aging process including primary aging at 1055oC for 1 hour and secondary aging at 845oC for 24 hours. However, the various selected temperature dropping program were performed during solution treatment to simulate the possible error of heating furnace. The maximum number of temperature dropping during solution treatment is varied from 1-3 times From all obtained results, the various temperature dropping during solution treatment conditions showed extremely the significant effect on the final rejuvenated microstructures and long-term gamma prime stability after heating at temperature of 900oC for 200 hours.

Morphology of γ Precipitates in Ni-Rich γ'-Ni3 (Al,Ta)

1972 ◽  
Vol 30 ◽  
pp. 588-589
Author(s):  
B. H. Kear ◽  
J. E. Doherty ◽  
A. F. Giamei ◽  
L. P. Lemaire
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
Binary System ◽  
Base Alloy ◽  
Ti Alloy ◽  
Nickel Base Alloy ◽  
New Findings ◽  
The Matrix ◽  
Nickel Base ◽  
Cuboidal Precipitate

The microstrueture of a commercial nickel-base alloy normally consists of a coherent, cuboidal precipitate of γ’ (alloyed Ni3Al) in a matrix of γ (Ni solid solution). Recently, Ham et al., working with the ternary alloy 78Ni-l8Al-4Ti (a/o), have shown that by appropriate heat treatment a completely novel microstrueture can be developed, in which the matrix is γ’ and the precipitate is platelet γ. The present study represents an extension of this work, and reports some new findings on precipitation of γ in γ’ in alloys similar in composition to the Ni-Al-Ti alloy but with Ta replacing Ti.The alloys used were solutionized in the range 2200-2400°F and aged at l600°F for 24hrs (giving ∼ 10 vol. percent of γ in γ’). According to our most recent findings, unlike the binary system, the solubility of γ’ for γ reaches a maximum at ∼ 2200°F in these alloys.

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