Who has a good materials properties book? I am looked for the strongest
known material using the following idealized test. You have a plate that
is maybe 1 cm thick. The plate is arbitrarily large and is oriented
vertically. Along an otherwise straight vertical edge is a projection
which measures 1x1x1. The projection is loaded once uniformly across its
top surface and the load is increased until it breaks. What material
would the plate be made of to hold the greatest weight before the
projection breaks off?
The geometry of the projection can be changed to a more intelligent
design if it helps in thinking about the problem, such as adding fillets
at the corners, but all materials must be compared using a single fixed
design. The material does not necessarily have to be metallic, but I
suspect it will be. I guess one more criterion is that the material can
actually be manufactured in macroscopic dimensions at the current time.
So that while diamond might theoretically be the strongest, a large 1 cm
thick plate of it can not be manufactured. I am not a structural
engineer, but I assume the determining factor here is simply the
ultimate tensile strength. If so, the winner I have found so far is AISI
Grade 18Ni (350) Maraging Steel with an ultimate strength of 355 ksi.
Can anyone beat this?
350 grade maraging? No way. I wouldn't trust it to take any shock
loading, and I wouldn't trust it to stand up to hydrogen embrittlement
potential problems during manufacture. (i.e., did you pickle that
puppy? Or perhaps electroplate it to increase corrosion resistance?
If so, make sure you've got a good test program, with enough samples
to give good statistics. And stand back from your loading apparatus.)
As a practicing metallurgist (25 years) I'd first consider AerMet
100, a proprietary alloy from CarTech. Yeah, the multiphase alloys of
Latrobe (MP35N and MP159) will possibly have higher strength, but they
depend on work hardening- and you'll only get that in smaller sizes.
The AerMet, being a vacuum melted PH alloy, will strengthen in even
large (6 inch) sections. It's available, machinable, less expensive
than the MP alloys, and readily heat treated. So, I suggest you use
that as your starting point, and try to find something that'll beat
Depending on your loading conditions, carburized 9310 might be the
best. Remember that carburized steels have that sweet compressive
residual stress layer. Take a look at the November 1978 issue of
Metallurgical Transactions (told you I was an olde fart) for a lovely
article on the topic.
Remember that mechanical properties are statistical in nature, that
many failure situations are flaw-size controlled, so if you go up in
size the wonderful properties available in the laboratory don't
translate into reality. If you're making a real part, make it of a
Thanks for the reply. That's the kind of help I was hoping to get. I
know experience is often discounted these days but I still have a lot of
respect for it.
I was aware of AerMet 100 and MP35N and looked them up before. Their
ultimate strength is both the same at 300 kpsi. The only reason I
suggested 350 maraging steel is that at 355 kpsi it seemed to be the
strongest thing around. But as you say, perhaps there are other factors
I should consider. I'm not too concerned with brittleness in my
application. In fact, it is preferable that it break first without
bending much beforehand. Although, it doesn't really matter either way
because I would also use a very elastic material if it had an even
higher ultimate strength. Corrosion resistance is probably not critical
either because the device is to operate in a benign room temperature
To be more specific about the actual part, it is a gear-like disk about
2" in diameter and 5mm thick. The teeth are used to lock a position and
not transmit motion so there are no restrictions on the shape of the
teeth and they will be designed for maximum strength only, which I am
also working on at the moment. The design of the part and the selection
of the material are two separate issues and I simplified my initial
posting so it wouldn't confuse the two. The normal load profile will be
a uniform increase from 0 to max in about 1 second. I don't know if you
would consider that shock loading, but applying maximum force
instantaneously will not occur.
So I guess my question is, given this further information and these
specific dimensions, assuming I could find a manufacturer with enough
expertise in maraging steel to be able to avoid any of the potential
problems you mentioned - given all this would you still recommend AerMet
Gearloose is correct. Other carburizing grades like 4320 and 8620
are easier to work with and have tougher cores tah 9310. In your
application shear force is constant, bending stress decreases with
depth, and contact force dependents on thw contact geometry. You must
design for each stress and compromise - that's the sign of a true
engineer. Each of these forces can be calculated analytically or with
FEA - preferably both - based on geometry.
E Vojcak PE
Yeah, Ed and Gearloose have the right idea.
When I was a student metallurgist 7 years ago I often wondered why we
didn't make everything out of maraging steels - going by Ashby's
diagrams, they were the solution to all metallurgical problems.
Now that I am a little older (and a little wiser) I'll say give me a
8620-ish composition steel(anything with about 0.2C, 3 Ni, 1.3Cr with
a dash of Mn, Si and Mo) with a 410HV core and 1.5mm carburised case
and it'll solve 98% of steel-related problems that I see in my line of
work of transmission drives. I've had some competitors get a 100J
charpy toughness doing that - still stumped on that one (any ideas
Unless you're looking at a very exclusive scenario e.g. extremely high
temps or corrosive conditions (I'm afraid the component that started
this thread doesn't fit category in my books) you are best off
selecting what Ed and Gearloose suggest. And best of all, it won't
cost much either and is easy to obtain.
Gearloose: I've always held the candle for 9310 / 9315 / 9317 but my
Timken maunal says they're "Former standard steels" - can one still
get the stuff nowadays?
Ed: Surely 9310 should have a higher toughness than 4320 & 8620?
Pls send replies to NG, not e-mail address.
Doug- for your part, I'd still not recommend the Maraging 350, due to
concerns about toughness (i.e. resistance to catastrophic crack
propagation). I'd go with the lower strength AerMet 100 in preference
to the maraging 350, or even over AerMet 310. Yet if you are not
going to worry about fracture toughness, then something else to
consider would be tool steels. A2 is a fine grade, as it doesn't have
a lot of carbides to act as crack initiation sites and air hardens to
above Rc60: it is 'stronger' than either AerMet or maraging 350. The
tensile strength of hardened tool steels is rarely published since
getting good test values is difficult: "?nonaxiality of specimen
alignment causes erratic results." (Roberts & Cary, TOOL STEELS, 4th
Edition) If resistance to deformation is one thing you seek, then
tool steels can provide.
I prefer air hardening steels when I can use them, as they have less
residual stress that can hurt your application. I also feel that the
lack of carbides in the A2 grade will help in your application, akin
to the theory of the olde 'matrix steels' of Teledyne Vasco, who
adjusted M2 tool steel composition so as to remove the carbides.
Lower wear resistance, higher toughness was the grail they got.
That said, I've got to agree with Ed and Ian who propose carburized
steel, if the part is appropriate for the process. Remember you have
to put it in a carburizing furnace and at some point quench in oil.
Given your part is 5 mm thick, a standard rule of thumb would be 0.8
mm case thickness, giving you about twice as much core as case. I've
long preferred 9310, but recognize that perhaps I've bought into the
hype. 9310 is commonly available as a vacuum melted grade, which
looks good for us aerospace guys, and has lower carbon content in the
core, AND in the case- the nickel reduces the eutectoid carbon
content. I interpret lower carbon content as having higher toughness,
yet I have no direct evidence of that. Ed, do you believe the 9310
mystique more smoke than reality?
It is readily available, by the way. We get it from Latrobe, Atlas,
and Republic, per AMS 6260 or AMS 6265, the latter being the vacuum
Ed, do you believe the 9310
9310 is a difficult steel to machine and heat treat (must anneal for
microstructure and stress relieve for hardness) and in my opinion not
the best choice for the part proposed in the orginal post - 9310
hardens too deep for such as small sized application. 8620 or 4320
would be more appropriate. The strongest material does not
necessarily make the stongest part.
In general 9310 has a core toughness of about 140 Mpa sqrt(m)or 125
ksi sqrt(inch)see Thomas/Patel CARBURIZING Processing and Performace
ASM. I can't find data on 8620 or 4320.
Ed Vojcak PE
With respect for all of you and your professions, you people are thinking old
news. Covalent composites are the way to go. Atomically precise fullerene
alloys. Vacuum deposition diamondoids. Nanostructured materials.
Shatter-resistant Nano Ceramics that are far stronger, tougher, and harder than
steel, while possessing steel like deformation capabilities. Conventional
smelted steels, concretes, and cement are on the way out. Get with the new, out
with the old.
Fine...the SAME rules of stress still apply!
Besides..where do I order these materials???? Got a source??
What is the distribution of mechanical properties for these so-called
new materials? What are their reliability?
I am old enough to remember the "Composits revolution" and how steel
was "old hat" funny we still use steel and composites, well they have
found a few homes in expensive items.
It would be nice to live with Capt. Kirk and Spock in the "future" but
we live here NOW - when your old enough you'll understand, you will
also understand that predictions of the future and buzz words are
often laughted at as a sign of "ignorance of the times" as viewed in
the REAL future.
Get in the practical and out with the buzz words.
Ed Vojcak PE
Are you still an injection mold press operator?
I really think that hot shot "researchers" who read internet blurbs and
can't understand them are excellent mature sources of criticism of
educated experienced old farts.
SpyKnife..... was one of your previou ghost names... and you had this
fettish about use of every new materials rumor to make better knives.
Nothing like a young fart.
You haven't changed.
You might be a lot of fun when you grow up and gain some education.