4. Superalloys are state-of-the-art metals used in engineering. One family of su

Question

4. Superalloys are state-of-the-art metals used in engineering. One family of superalloys areknown as Inconel alloys that are based on nickel and chromium. They are used primarily fortheir extreme corrosion and oxidation resistance even at high temperatures. This resistance is thereason why companies like SpaceX, Tesla, Ford, Rocketdyne and many others use them inhighly corrosive high temperature applications. For example, SpaceX actually 3D prints rocketengine manifolds using Inconel and direct metal laser sintering from powder metal precursors!Tesla achieves “Ludicrous Mode” (0 to 60 in 2.8 seconds!) by using this alloy in the batterycontainer which allows 1500 A of current instead of a paltry 1300 A.

(a) Look up Inconel 690 alloy here and determine what the atomic percent of iron in this alloy is.

(b) If the density of Inconel 690 is 8.19 g/cc, how many iron atoms would be present in 1 cm3?

(c) The reason Inconel alloys are so corrosion and oxidation resistant is because of the highchromium content. Chromium reacts with oxygen in air to form a passivating layer of Cr2O3which prevents subsequent oxidation. Determine the valence of chromium and specific what typeof bonding is present in Cr2O3 (support with calculation).

(d) Which are the bonding electrons for both chromium and oxygen (Specify one of thesebonding electrons by its configuration and write its quantum number)?

Explanation / Answer

1.Superalloys:are successful today because they have solved pressing demands for durability and
strength in machines and systems that were barely imaginable a hundred years ago. Superalloys
have helped us conquer air and space, plumb the depths of the earth and ocean, and address
many other challenges of modern life.

As such, they deserve to have their story told. The nature of this industry, however, makes the
telling a challenging task. Its history is one of many small events and inventions that took place
across the boundaries of nations, industries and countries. Many individuals contributed to the
state of the art today, and only a few left their names in the scattered records.

This paper is an attempt by one of those individuals who has been witness to many of the
industry’s milestones to combine eyewitness history with industry research and begin to set the
story down in print. It is hoped that we can begin the dialog needed to create a complete history,
and set the stage for a view of the superalloy industry’s bright and exciting future.

Because it is, to some extent, a first person account, I would like to state that this paper has a
bias. It is written by an engineer who spent his career working for a superalloy mill; furthermore
a mill that was a pioneer in the industry. With full disclosure out of the way let me close this
introduction with the following: Alloy 718, Waspaloy and their derivatives are the most
successful alloy systems of our time. Their success is due to a combination of factors that include
the properties and performance of superalloys in service, the added value provided by vacuum
melting, the success of gas turbines and the continuous development of superalloys and the

oxidation resistance even at high temperatures

The improvement in oxidation resistance of high temperature alloys as a result of additions of rare earth elements, other reactive metals, or dispersions of stable oxides, has been known for many years. Two effects seem the most important: first, the adhesion between scale and alloy is markedly improved and this increases the alloy's resistance to thermal cycling exposure; secondly, in some but not all cases the actual growth rate of the oxide is also reduced. The various models proposed to explain these phenomena are discussed in the light of currently available experimental evidence. The most significant of these involve modification to the early, transient stages of oxidation, doping of the oxide which changes its transport properties, mechanical keying of the surface scale to the substrate by the formation of intrusions of oxide penetrating into the alloy and the elimination of void formation at the alloy-scale interface. The efficacies of the various beneficial additions are compared.

Earlier this year, we wrote about SpaceX transferring some technology and welding equipment to Tesla. Now it seems like the new “Ludicrous” upgrade might have been made possible due to knowledge acquired through rocket engine manufacturing at SpaceX.

The Ludicrous upgrade consists of 2 improvements to the electronics of the Model S’ battery pack. The first improvement is the replacement of a standard fuse to an “advanced smart fuse” which enables the monitoring of current to the millisecond, and makes it possible to cut the power with “extreme precision”.

The second improvement is where SpaceX’s expertise might have come into play. Tesla replaced the main pack contactor to use Inconel instead of steel. Inconel is a space-grade superalloy well suited for extreme high temperature environments. This superalloy is primarily use in the aerospace industry, and one of its more famous use is in the novel manufacturing process of SpaceX’s

The Panasonic DMC-GH3 Lumix Body (Black), is a new and highly evolved model from LUMIX, creator of the world’s first digital single lens mirrorless (DSLM) camera.

The body has been engineered to incorporate a 16.05-megapixel Digital Live MOS Sensor, a 4-CPU Venus Engine, and a newly designed low-pass filter. The creative expression made possible by these innovations, render even the finest textures in intricate detail, breaking new ground in photographic realism. The new model also features Contrast AF with a high level of response. And its magnesium alloy frame is tightly sealed to resist splashes and dust, making the DMC-GH3 rugged enough to withstand the rigors of professional use.

Features:

In addition to supporting a wide range of recording formats, the DMC-GH3 features a special heat-dispersing design for extended high-quality recording. Its specifications match those of many professional cameras, ensuring that it meets the demands of video field work. The LUMIX GH3 was designed from the ground up to provide seamless multi-media performance for both stills and videos. It may well be the world’s first camera to please professional photographers by offering them the best of both.

The DMC-GH3 features a 16.05-megapixel Digital Live MOS Sensor with a level of sensitivity that produces flowing gradation from shadows to highlights. High resolution and a wide dynamic range create truly stunning images that look like you could reach out and touch them. High-sensitivity ISO 12800 (extended: ISO 25600) and extensive noise reduction give you remarkable images even in dim lighting.

In the DMC-GH3’s Contrast AF system, the image sensor doubles as the AF sensor to resist any mechanical margin of error. Compared with Phase Difference AF, the focusing is precise even at small F-numbers. A faster sensor and engine also achieve a higher focus detection speed than most traditional DSLR models.

The DMC-GH3 gives you 1920 x 1080 60p [NTSC] / 50p [PAL] Full-HD recording. Progressive scanning records every frame, so the amount of data contained is twice that of interlace scanning, and the images have extremely high definition.

a)Effects of Alloy Elements
Alloy properties are determined by alloying compositions, phase constitution, and
structure. Alloying elements and their quantity are the most important factors to be
considered in the alloy design for the desired structure and thus the required properties.
Cr, Ni and Fe are three major alloy elements in high temperature alloys. As shown
in Figure 1, the quantities of these three elements in an alloy could decide the phase
constitution, structure and thus properties.
As mentioned previously, Cr is a primary element for forming oxide scales for
providing surface stability of high temperature alloys. To have enough oxidation and
corrosion resistance at the SOFC operating temperatures, ideally the amount of Cr in
most high temperature alloys should not be less than a number around 18%, as described
previously. In addition, Cr is also an important element for improving mechanical
properties through solid solution strengthening and carbide hardening by forming Cr7C3
and Cr23C6. In Fe-base high temperature alloys, including superalloys and stainless steels,
Cr, by producing the gamma loop in Fe-Cr phase diagram (Figure 2), can be utilized to
stabilize ferrites and destabilize austenite. For the pure Fe-Cr system, a minimum of 13
wt% Cr is required to maintain the BCC ferritic structure from RT to the melting point.
For martensitic stainless steels, the Cr content cannot be too high, normally less than
18%, in order to generate austenite at high temperatures, which transforms to martensite
during subsequent cooling. In Cr-base alloys, a BCC crystal structure is maintained
which contributes to thermal expansion matching with other SOFC components.
Though the addition of more Cr increases the oxidation resistance and also helps
stabilize the BCC ferritic structure for a TEC match, increased Cr concentration could
also lead to some disadvantages for SOFC applications. As shown in the Fe-Cr phase
diagram in Figure 2, a second phase, called the sigma phase, can precipitate along grain
boundaries in the alloy matrix at a temperature in the range of 550~870o
C when the
concentration of Cr is higher than 14~15 wt% [11]. The formation of sigma phase along
grain boundaries not only causes a lower ductility (sigma phase embrittlement), but also
results in deteriorated oxidation resistance as well as thermal expansion mismatch in
SOFC, as indicated in our recent studies[25]. It is also reported that increasing Cr
contents in ferritic structures decrease the thermal expansion coefficient of alloy
compositions, but also creates “knees” in the thermal expansion curves if the Cr
concentration becomes too high [26].
As indicated by many studies [14,18~20, 22], the resistance of the chromia scale
will reach an unacceptable level after hundreds of hours under current SOFC operating
conditions. Accordingly, it appears that the high temperature alloys have to be modified
so as to inhibit the growth of the chromia scale and decrease the resistance of the scale.
One effective approach is to change the bulk or surface chemistry by adding reactive
elements, such as Y, Ce, or La (or their oxide forms). These elements, when added as a
trace amount (0~0.1%) to the alloys, significantly modify the growth behavior

Alloys Elastic
modulus
(GPa)
Yield
strength
0.2 (MPa)
Creep
strength T (MPa)
Rupture
strength T t (MPa)
Superalloys
Carpenter
19-9DL
138 at 815o
C Co 732
1 105 × =36 Co 816
1 103 × =59
Incoloy
556TM
148 at 800o
C 220 at 760o
C Co 760
1 105 × =59
Aktiebolag
253 MA
115 at 760o
C 110 at 750o
C Co 760
1 105 × =29
Haynes

b)

Super alloys have good creep and oxidation resistance. They are also known as high performance alloys, and can be formed in different shapes. Work hardening, precipitation hardening, and solid-solution hardening are performed for strengthening the super alloys. These alloys have the capcity to function at very high temperatures and severe mechanical stress, and also where high surface stability is required.

Inconel 690™ is a nickel-chromium alloy. It has high resistance to hot gases or oxidizing chemicals due to the presence of high chromium content. The following datasheet gives an overview of Inconel 690

Mechanical Properties
INCONEL alloy 690 has high strength over a broad range of temperatures. Mechanical properties of the alloy vary with
product form and temper. Alloy 690 is normally used in the annealed temper, and strength characteristics described below are
representative of annealed material. The usual annealing temperature is approximately 1900°F (1040°C). The effect of
different annealing temperatures on the tensile properties of cold-worked material is shown under “Fabrication” in Figure 8.
Tensile Properties
At room and elevated temperatures, INCONEL alloy 690
displays high yield and ultimate strengths along with good
ductility. Table 5 lists results of room-temperature tensile
tests on annealed material. As indicated by the values,
tensile properties may vary with product form and size. At
high temperatures, alloy 690 retains a substantial level of
tensile properties with temperatures of over 1000°F (540°C)
required to produce significant declines in strength. Figure
1 shows the results of short-time tensile tests performed at
temperatures to 1800°F (982°C). The curves represent
average values for both cold-worked and hot-worked
products in the annealed temper.
Fatigue Strength
The results of low-cycle fatigue tests performed at room
temperature are shown in Figure 2. The specimens were
tested under axial strain with fully reversed loading.

R-41
169 at 800o
C 752 at 760o
Co 732
1 103 × =234 Co 816
1 103 × =165
Inconel
625
160 at 760o
C 421 at 760o
Co 760
1 103 × =234 Co 816
1 103 × =96
Pyromet
680
144 at 816o
C 241 at 760o
Co 732
1 105 × =55 Co 816
1 103 × =62
Stainless steels
AL 446 200 at RT 275* at RT
55* at 760o
C
Co 760
1 105 × =7.6 Co 760
1 103 × =13.5
Carpenter 443 200 at RT 345 at RT
41 at 760o
C
Co 704
1 104 × =7.0
AL 439 HPTM

200 at RT 310 at RT
48 at 760o
C
Co 816
1 103 × =7.0
AL 441 HPTM

200 at RT 290 at RT
58 at 760o
C
Co 816
1 103 × =11.0

c)1. High thermodynamic stability of the scale that is formed.
2. Low scale growth rates.
3. Good scale adhesion to the metal surface.
4. The potential for scale healing following surface damage or cracking.
5. Thermal expansion coefcient matched to the substrate.
6. High strain tolerance of the scale.
7. Good erosion resistance.
8. High scale melting temperature.
9. Low scale vapour pressure.
Of the corrosion products that may be produc

Alloy Composition and Microstructure
The primary constituents of Alloy 600 and its weld metals, Alloy 82 and Alloy 182, are nickel,
iron and chromium (Ni-Fe-Cr); a table of compositions for common Ni-Fe-Cr alloys is given in

d)

The electron configuration of an atomic species (neutral or ionic) allows us to understand the shape and energy of its electrons. Many general rules are taken into consideration when assigning the "location" of the electron to its prospective energy state, however these assignments are arbitrary and it is always uncertain as to which electron is being described. Knowing the electron configuration of a species gives us a better understanding of its bonding ability, magnetism and other chemical properties.

Introduction

The electron configuration is the standard notation used to describe the electronic structure of an atom. Under the orbital approximation, we let each electron occupy an orbital, which can be solved by a single wavefunction. In doing so, we obtain three quantum numbers (n,l,ml), which are the same as the ones obtained from solving the Schrodinger's equation for Bohr's hydrogen atom. Hence, many of the rules that we use to describe the electron's address in the hydrogen atom can also be used in systems involving multiple electrons. When assigning electrons to orbitals, we must follow a set of three rules: the Aufbau Principle, the Pauli-Exclusion Principle, and Hund's Rule.

The wavefunction is the solution to the Schrödinger equation. By solving the Schrödinger equation for the hydrogen atom, we obtain three quantum numbers, namely the principal quantum number (n), the orbital angular momentum quantum number (l), and the magnetic quantum number (ml). There is a fourth quantum number, called the spin magnetic quantum number (ms), which is not obtained from solving the Schrödinger equation. Together, these four quantum numbers can be used to describe the location of an electron in Bohr's hydrogen atom. These numbers can be thought of as an electron's "address" in the atom.

Notation

To help describe the appropriate notation for electron configuration, it is best to do so through example. For this example, we will use the iodine atom. There are two ways in which electron configuration can be written:

I: 1s22s22p63s23p64s23d104p65s24d105p5

or

I: [Kr]5s24d105p5

In both of these types of notations, the order of the energy levels must be written by increased energy, showing the number of electrons in each subshell as an exponent. In the short notation, you place brackets around the preceding noble gas element followed by the valence shell electron configuration. The periodic table shows that kyrpton (Kr) is the previous noble gas listed before iodine. The noble gas configuration encompases the energy states lower than the valence shell electrons. Therefore, in this case [Kr]=1s22s22p63s23p64s23d104p6.

Quantum Numbers

Principal Quantum Number (n)

The principal quantum number n indicates the shell or energy level in which the electron is found. The value of n can be set between 1 to n, where n is the value of the outermost shell containing an electron. This quantum number can only be positive, non-zero, and integer values. That is, n=1,2,3,4,..

For example, an Iodine atom has its outmost electrons in the 5p orbital. Therefore, the principle quantum number for Iodine is 5.

Orbital Angular Momentum Quantum Number (l)

The orbital angular momentum quantum number, l, indicates the subshell of the electron. You can also tell the shape of the atomic orbital with this quantum number. An s subshell corresponds to l=0, a p subshell = 1, a d subshell = 2, a f subshell = 3, and so forth. This quantum number can only be positive and integer values, although it can take on a zero value. In general, for every value of n, there are n values of l. Furthermore, the value of l ranges from 0 to n-1. For example, if n=3, l=0,1,2.

So in regards to the example used above, the l values of Iodine for n = 5 are l = 0, 1, 2, 3, 4.

Magnetic Quantum Number (ml)

The magnetic quantum number, ml, represents the orbitals of a given subshell. For a given l, ml can range from -l to +l. A p subshell (l=1), for instance, can have three orbitals corresponding to ml = -1, 0, +1. In other words, it defines the px, py and pzorbitals of the p subshell. (However, the ml numbers don't necessarily correspond to a given orbital. The fact that there are three orbitals simply is indicative of the three orbitals of a p subshell.) In general, for a given l, there are 2l+1 possible values for ml; and in a n principal shell, there are n2 orbitals found in that energy level.

Continuing on from out example from above, the ml values of Iodine are ml = -4, -3, -2, -1, 0 1, 2, 3, 4. These arbitrarily correspond to the 5s, 5px, 5py, 5pz, 4dx2-y2, 4dz2, 4dxy, 4dxz, and 4dyzorbitals.

Spin Magnetic Quantum Number (ms)

The spin magnetic quantum number can only have a value of either +1/2 or -1/2. The value of 1/2 is the spin quantum number, s, which describes the electron's spin. Due to the spinning of the electron, it generates a magnetic field. In general, an electron with a ms=+1/2 is called ­­an alpha electron, and one with a ­ms=-1/2 is called a beta electron. No two paired electrons can have the same spin value.

Out of these four quantum numbers, however, Bohr postulated that only the principal quantum number, n, determines the energy of the electron. Therefore, the 3s orbital (l=0) has the same energy as the 3p (l=1) and 3d (l=2) orbitals, regardless of a difference in l values. This postulate, however, holds true only for Bohr's hydrogen atom or other hydrogen-like atoms.

When dealing with multi-electron systems, we must consider the electron-electron interactions. Hence, the previously described postulate breaks down in that the energy of the electron is now determined by both the principal quantum number, n, and the orbital angular momentum quantum number, l. Although the Schrodinger equation for many-electron atoms is extremely difficult to solve mathematically, we can still describe their electronic structures via electron configurations.

General Rules of Electron Configuration

There are a set of general rules that are used to figure out the electron configuration of an atomic species: Aufbau's Principle, Hund's Rule and the Pauli-Exclusion Principle. Before continuing, it's important to understand that each orbital can be occupied by two electrons of opposite spin (which will be further discussed later). The following table shows the possiblenumber of electrons that can occupy each orbital in a given subshell.

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