Morphology, Distribution and Identification of Micro-Constituents Along Grain Boundaries in Nickel-Base Alloys

1973 ◽  
Vol 31 ◽  
pp. 176-177
Author(s):  
D. E. Fornwalt ◽  
A. R. Geary ◽  
B. H. Kear
Keyword(s):  
Electron Microscope ◽  
Grain Boundaries ◽  
Volume Fraction ◽  
Rupture Life ◽  
Stress Rupture ◽  
High Volume ◽  
Precipitate Morphology ◽  
Stress Rupture Life ◽  
Nickel Base ◽  
Scanning Electron

A systematic study has been made of the effects of various heat treatments on the microstructures of several experimental high volume fraction γ’ precipitation hardened nickel-base alloys, after doping with ∼2 w/o Hf so as to improve the stress rupture life and ductility. The most significant microstructural chan§e brought about by prolonged aging at temperatures in the range 1600°-1900°F was the decoration of grain boundaries with precipitate particles.Precipitation along the grain boundaries was first detected by optical microscopy, but it was necessary to use the scanning electron microscope to reveal the details of the precipitate morphology. Figure 1(a) shows the grain boundary precipitates in relief, after partial dissolution of the surrounding γ + γ’ matrix.

Influence of Heat Treatment on γ´ Phase and Property of a Directionally Solidified Superalloy

2018 ◽  
Vol 37 (3) ◽  
pp. 271-276
Author(s):  
P. C. Xia ◽  
K. Xie ◽  
H. Z. Cui ◽  
J. J. Yu
Keyword(s):  
Heat Treatment ◽  
Aging Temperature ◽  
Volume Fraction ◽  
Rupture Life ◽  
Stress Rupture ◽  
Nickel Base Superalloy ◽  
Directionally Solidified ◽  
Stress Rupture Life ◽  
Stress Rupture Property ◽  
Nickel Base

AbstractThe effects of heat treatment process on microstructure and properties of a nickel base superalloy are investigated. The size of γ´ phase decreases and the stress rupture life of alloy at 1100 °C/60 MPa drops with the rise of cooling rate. The hardness at room temperature also increases. The size of cuboidal γ´ precipitate and the volume of spherical γ´ precipitate increase with the rise of aging temperature. With higher aging temperature, the alloy exhibits bimodal γ´ phase. A reasonable combination of the size and volume fraction of cuboidal and spherical γ´ phase can obtain better stress rupture property at 1100 °C/60 MPa.

High-Temperature, Cobalt-Tungsten Alloys for Aerospace Applications

1965 ◽  
Vol 87 (1) ◽  
pp. 9-20 ◽  
Author(s):  
J. C. Freche ◽  
R. L. Ashbrook ◽  
G. D. Sandrock
Keyword(s):  
High Temperature ◽  
Rupture Strength ◽  
Rupture Life ◽  
High Stress ◽  
Stress Rupture ◽  
Stress Rupture Life ◽  
Tungsten Alloys ◽  
Aerospace Applications ◽  
Temperature Capability ◽  
Nickel Base

The high-temperature capability and workability of cobalt-tungsten alloys for aerospace applications is discussed. The average life at 1850 F and 15,000 psi of the strongest previously reported alloy, Co-25 W-1Ti-1Zr-0.4C, was doubled from 92 to 185 hr by small additions of chromium and rhenium. At 2200 F and 5000 psi, the strongest alloy, Co-25W-1Ti-1Zr-3Cr-2Re-0.4C, had a rupture life of 23 hr; the elevated-temperature rupture strength compared favorably with the strongest available conventional (high-chromium) cobalt-base alloys. Above approximately 2035 F and at reasonably high stress levels (10,000 and 15,000 psi), its stress-rupture life also exceeded those of the strongest known nickel-base alloys, including the NASA tantalum-modified alloy and SM-200. It is particularly significant that even the strongest alloys of this series were readily hot-rolled. Ingots 1/2 in. thick were reduced to 0.065-in. sheet and subsequently cold-rolled to 0.0125-in. sheet. Elongations as high as 31 percent were obtained at room temperature with annealed sheet specimens. The good ductility obtained suggests that these alloys could be fabricated into complex shapes required for various aerospace and other applications. Although the strongest alloys had a chromium content of only 3 percent, they did not oxidize catastrophically in air.

The Role of Solidification Rate on Fiber Distribution and Mechanical Properties of a Directionally Solidified Nickel Base-Tac Eutectic

1981 ◽  
Vol 12 ◽  
Author(s):  
John L. Walter
Keyword(s):  
Base Alloy ◽  
Solidification Rate ◽  
Rupture Life ◽  
Stress Rupture ◽  
High Strength ◽  
Directionally Solidified ◽  
Fiber Density ◽  
Alloy Matrix ◽  
Stress Rupture Life ◽  
Nickel Base

ABSTRACTA nickel base-TaC eutectic alloy consisting of 53 wt % Ni, 11 W, 3 Re, 5 Co, 3 Mo, 2 Al, 21.67 Ta and 1.33 C was directionally solidified at rates from 0.32 to 3.8 cm/hr. Samples were taken from the regions of aligned TaC fibers and tested in tension at 1000°C and in stress-rupture. The fiber density increased from 1×106 fibers/cm2 at 0.32 cm/hr to 27×106 fibers/cm2 at 3.8 cm/hr. The stress-rupture life at 927°C and 275.6 MPa ranged from 4 hrs for samples solidified at 0.32 cm/hr to 4187 hrs for the sample solidified at 2.54 cm/hr at which time the test was terminated. Examination, by transmission electron microscopy, of the samples tested at 1000°C in tension, to just the beginning of fiber breakage, revealed a change in the mode of deformation of the nickel-base alloy matrix with increasing fiber density. It was also seen that the TaC fibers deformed by two mechanisms; by slip and by the formation of stacking faults.It appears that tailoring the alloy composition to allow for higher solidification rates may be a more effective strengthener than alloying the matrix for high strength.

Influence of Carbides on Stress Rupture Property of a Ni-Base Superalloy

2016 ◽  
Vol 849 ◽  
pp. 520-525
Author(s):  
Zhen Rui Li ◽  
Ning An
Keyword(s):  
Rupture Life ◽  
High Stress ◽  
Stress Rupture ◽  
Fracture Morphology ◽  
Stress Rupture Life ◽  
Stress Rupture Property ◽  
Moderate Number ◽  
Carbide Size ◽  
Base Superalloy ◽  
Scanning Electron

This study aims to explore the influence of morphology and distribution characteristic of carbides on stress rupture property at high temperature. The stress rupture life at 850°C/325MPa was tested. Meanwhile, microstructure and fracture morphology of stress rupture specimens were observed by scanning electron microscopy. The types of carbides were identified and the carbide size was also measured. The results show that the alloys with small size, uniformly distribution and moderate number of carbides present a high stress rupture performance.

Effects of Long-Term Aging at 1070°C on Microstructure and Mechanical Properties of Ni3Al-Base Alloy IC6E

2010 ◽  
Vol 650 ◽  
pp. 205-209 ◽  
Author(s):  
Ming Li ◽  
Jin Xia Song ◽  
Shu Suo Li ◽  
Ya Fang Han
Keyword(s):  
Mechanical Properties ◽  
Grain Boundaries ◽  
Base Alloy ◽  
Rupture Life ◽  
Stress Rupture ◽  
Stress Rupture Life ◽  
Microstructure And Mechanical Properties ◽  
Stress Rupture Properties ◽  
Essential Change

The effect of long-term aging at 1070°C on microstructure and mechanical properties of Ni3Al-base equiaxed superalloy IC6E was investigated. The microstructure change during aging for periods of 100 to 1500h was examined by SEM . Results showed that alloy IC6E underwent following microstructure changes during aging: γ' phases coalesced and grew, γ phases became disconnected and coarsened, the content of Mo (the solution-hardening element of γ and γ' phases) in γ' phases decreased, Y-NiMo phases precipitated from γ phases both at grain boundaries and within grains, and γ' bands and large γ phases emerged along grain boundaries. The tensile and stress rupture properties after aging were determined. The results showed that the yield strength of alloy IC6E at room temperature decreased obviously after aging for 100 h, and reduced slowly during further aging. The stress rupture life under 1070°C, 80MPa also had no essential change during aging.

Influences of W and Al on the Microstructure and Stress-Rupture Property of Re-Free Ni-Based Single Crystal Superalloys

2017 ◽  
Vol 898 ◽  
pp. 492-497
Author(s):  
Jing Yang Chen ◽  
Qing Li ◽  
Ming Jun Zhang ◽  
Xin Tang ◽  
Cheng Bo Xiao
Keyword(s):  
Single Crystal ◽  
Volume Fraction ◽  
Base Alloy ◽  
Rupture Life ◽  
Solidus Temperature ◽  
Stress Rupture ◽  
Stress Rupture Life ◽  
Stress Rupture Property ◽  
Matrix Channel ◽  
Liquidus Temperatures

The influence of W and Al on the solidus and liquidus temperatures, microstructure and stress-rupture property at 980 °C/250 MPa was investigated in three Re-free experimental Ni-based single crystal superalloys. The results indicated that the solidus temperature increased for 14.0 °C and 9.8 °C by adding 0.84 wt.% W only and adding 0.45 wt.% Al and 0.44 wt.% W to the base alloy, respectively. The γ′ morphology changed from nearly cuboidal in the base alloy to cuboidal by adding 0.45 wt.% Al and 0.44 wt.% W. The volume fraction of γ′ precipitates increased, while the γ channel width decreased after adding Al and W. The additions of Al and W improved the stress-rupture life at 980 °C/250 MPa because of higher γ′ volume fraction, narrower γ matrix channel and more complete rafting structure.

Fine Microstructure of a Mechanically Alloyed Oxide Dispersion Strengthened Nickel-Base Superalloy

1977 ◽  
Vol 35 ◽  
pp. 298-299
Author(s):  
Jordi Marti ◽  
Timothy E. Howson ◽  
David Kratz ◽  
John K. Tien
Keyword(s):  
Solid Solution ◽  
Volume Fraction ◽  
Stress Rupture ◽  
Oxide Dispersion Strengthened ◽  
Solid Solution Alloy ◽  
Oxide Dispersion ◽  
Creep And Stress Rupture ◽  
Mechanically Alloyed ◽  
Fine Microstructure ◽  
Nickel Base

The previous paper briefly described the fine microstructure of a mechanically alloyed oxide dispersion strengthened nickel-base solid solution. This note examines the fine microstructure of another mechanically alloyed system. This alloy differs from the one described previously in that it is more generously endowed with coherent precipitate γ forming elements A1 and Ti and it contains a higher volume fraction of the finely dispersed Y2O3 oxide. An interesting question to answer in the comparative study of the creep and stress rupture of these two ODS systems is the role of the precipitate γ' in the mechanisms of creep and stress rupture in alloys already containing oxide dispersoids.The nominal chemical composition of this alloy is Ni - 20%Cr - 2.5%Ti - 1.5% A1 - 1.3%Y203 by weight. The system receives a three stage heat treatment-- the first designed to produce a coarse grain structure similar to the solid solution alloy but with a smaller grain aspect ratio of about ten.

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