Forged titanium armor plate knives

[Mecha]

I've had the pleasure of working a few knives in a relatively new alpha-beta titanium alloy: ASTM grade 38, called ATI 425 by Allegheny Technologies Incorporated, the company that introduced this alloy in 2010. Among other uses (such as parts for the current Mars rovers), it functions as armor plating for military vehicles.

Continuing on with the snub-nosed knife shape:

The wrapped grips are recessed into the tang. These were forged and ground thin:

Grade 38 is interesting because of it's high iron content, which is a strong beta phase stabilizing element when alloyed into titanium, and also brings a potent deep-hardening effect into the mix. Iron disperses into very fine particles within a titanium matrix.

Grade 38 titanium chemical composition:

Compared to good ole' fashioned Grade 5 (6al4v), you can see that alpha stabilizer Aluminum was reduced by a third, and beta stabilizer Vanadium was reduced by half. Iron was then introduced to around 1.5% which is really high in a ti alloy, and produces interesting results during heat-treatment.


They started by shredding a bunch of teeth off of a new band saw blade cutting tabs from the armor plate:

Here they are ready for experimental heat treatment:

In keeping with the military hardware theme, a spent 105mm Howitzer shell was used as a quench tank. It's amazing that in a matter of seconds, quenching one of those thin little blades turns the whole reservoir of ice-cold water, filled to the brim, lukewarm including the brass itself. Yes, that is a USAF 105 shell! Crazy, right?

This alloy proved to be very heat-treatable has some fairly exciting potential for blades. The thin knives took a keen, fine edge. I like it. More must be made...

Thanks for looking. :]

 

[Lapedog]

Have you heard of these Ocean Master knives which are made of a titanium alloy which hardens to near 60rc?

 

[Mecha]

I've heard of them. I don't want to open the ti dive knife can of worms in this thread, but so far every ti dive knife I've inspected has been cheap junk that is 100% not what it claims to be. It's like there is a competition out there to see who can get the Chinese company that makes all ti dive knives to overheat the blades to the highest Rockwell number they can to increase marketability, even though Rockwell hardness tests are not a reliable indicator of the mechanical properties of heat-treated ti. I see that Oceanmaster has trademarked "Custom-Formulated Beta Titanium." When dive knife companies say "beta titanium" they don't mean the alloy's composition or crystalline structure, it's just a word that makes it sound good.

In general, Ti diving knives make ti knives look really bad. In a way, all diving knives are like my own personal Quarterm5ster. I suppose it's possible that Oceanmaster is legit, but I guess nobody will ever know since there is absolutely zero proof or substance to anything they say about the knives. Supposedly made in the USA.

http://www.oceanmaster.com/KnivesFeatures.htm#DiveKnife

http://www.discountcutlery.net/Ocean-Master-Knives_c_7169.html

 

[BladeScout]

Great looking knives.

Funny about the Ocean Master dive knives.
I was just looking at them yesterday but I held back for the exact reasons, that Mecha state.
On the Bay OM have a skeleton knife supposedly in Beta.
But man, ti knives have gotten a bad rep because of all the butter soft non-Beta knives put there.
They claim Beta - I have my doubts.

 

[Craig Daniel]

I like the style, I bet they will perform very well.

 

[mete]

Oxygen- is that an alloying element or a trace element ?? What does it do in the mix?
I'm glad to see that I'm not the only doubter about China !

 

[Lycosa]

My craving is BAD, mecha.
Thanks for making your knives.
rolf

 

[Lorien]

I like the style, I bet they will perform very well.

this style that Sam's developed does perform very well, from personal experience

and, let's not go down that road of China bashing please. Sam made his point well, so let's keep things on track here, no need to dogpile on it

 

[Dawkind]

More exceptional knives my friend...[emoji106][emoji482][emoji631]


Sent from my iPhone using Tapatalk

 

[Mecha]

Oxygen- is that an alloying element or a trace element ?? What does it do in the mix?
I'm glad to see that I'm not the only doubter about China !

I was also surprised at the high oxygen content left in this ti alloy. In general, higher oxygen levels mean less ductility and more "hardness" but by hardness we mean more resistance to the dislocation of groups of atoms - this means embrittlement and cracking. It also means more "strength," of course, HA! But that's in materials terms; the lower oxygen, more pure alloy is actually "stronger" in use.

Sort of like the story about the strong, haughty giant tree that was blown down in a windstorm, and as he lay dying, he asked the reeds how they, so slender and delicate, were able to survive the storm's winds, to which the reeds reply that bending with the winds is what gives them so much strength.

Oxygen levels are so important that Grades 1-4, all "commercially pure" titanium, are mainly categorized based on minute amounts of oxygen left in the alloy. The "dirtier" alloys are "stronger" but also can crack more easily, especially when the billet is getting twisted. I read that a single oxygen atom can cause a cascade of twisting cracks to form and branch off from it. There are a half-dozen different grades of 6al4v also based on oxygen content, and we're talking about just a fraction of a percentage here!

The oxygen/titanium relationship is complex and important to the properties of the alloy but there is a lot of information out there, with lots of research ongoing. Here's a good one:

https://www.ideals.illinois.edu/bitstream/handle/2142/45277/Henry_Wu.pdf?sequence=1

(I skipped the math part) Mete, I don't know why they leave so much the oxygen in this alloy. There is evidence that it can aid in the formation of Alpha Prime titanium martensite.

 

[Mecha]

Thank you Dawkind, Lycosa and Craig Daniel! They're just simple little things, but I bet they'll do pretty well, slicey and weightless. I wonder what Kohai999 has to say about them.

this style that Sam's developed does perform very well, from personal experience

and, let's not go down that road of China bashing please. Sam made his point well, so let's keep things on track here, no need to dogpile on it

I don't care where they're made, but they're definitely low-quality prybars. The ubiquitous "beta titanium dive knives" that all have the same gray finish and quasi-tactical look act almost like some sort of strong titanium pot metal. It's baffling how poorly the mystery ti is processed for even basic knife use. For example, the large, coarse grain:

It's important to note that "beta titanium" is a metallurgical term, that defines a ti alloy based on its ability to form stable crystal phases other than the natural "alpha phase" after a quench, which means lots of heat-treatment fun! Whether a ti alloy is alpha, alpha-beta, near-beta, or beta ti is defined by the ratio of alpha and beta phase stabilizing elements alloyed into the ti base metal. It's how all ti alloys are classified. So when something says "beta titanium" it would just mean that the alloy has a certain percentage of some beta stabilizer that pushes the phase change stability over the top, sort of like how chromium over 10.5% or so in carbon steel suddenly makes it "stainless." There can be beta ti alloys that can make way better blades than others, and the ideal heat-treatments and processing for them would all vary. The phase stability is just the beginning, since all alloying elements impart different characteristics to the final product.

So don't get ripped off: know your titanium! Beta is just a word, after all, that can be used (or trademarked) without any meaning.

 

[mete]

Thanks Mecha .and for skipping the math !! Most of the computational stuff is beyond me .But it shows that if you understand all the details you can do interesting things with alloys. Oxygen is often thought of as bad so you have to get beyond that !!
Back in school one of the guys did a thesis on superplasticity where the Ti alloy was stretched an incredible amount , just like pulling taffee ! That was a neat visible thing to show what can be done. Metallurgy is fun !!

 

[Revolverrodger]

What is your feeling on the beta titanum used by mission knives.
I have the MPS Ti and it performs pretty good and is so light !

 

[Mecha]

Thanks Mecha .and for skipping the math !! Most of the computational stuff is beyond me .But it shows that if you understand all the details you can do interesting things with alloys. Oxygen is often thought of as bad so you have to get beyond that !!
Back in school one of the guys did a thesis on superplasticity where the Ti alloy was stretched an incredible amount , just like pulling taffee ! That was a neat visible thing to show what can be done. Metallurgy is fun !!

Damn right, super fun. Was the taffy ti heated to exactly it's beta transus temperature?

Being bad at math was pretty much a prerequisite for even attempting to make beta ti swords.

 

[Mecha]

What is your feeling on the beta titanum used by mission knives.
I have the MPS Ti and it performs pretty good and is so light !

I've never seen one in person and have always heard good things about them. I heard the alloy they use is Beta C, which is a good old-school and readily-available beta ti formula that holds a big variety of alloying elements. But I don't know for sure what alloy they use, or what their heat-treatment schedule is like, just that people hold them in high regard.

 

[Lycosa]

If I may, my MPF Ti folder has never let me down.
Their Titanium is proprietary.
rolf

 

[Mecha]

If I may, my MPF Ti folder has never let me down.
Their Titanium is proprietary.
rolf

Aye, damn I would love to take a tour of their facility, it would be an eye-opener for a hammer-swinger like me, for sure.

 

[JayGoliath]

Sam,

I have seen the similar through a Strider-Horton collaboration, using Beta Ti Level 4 strike plate.
The edge was carbidized for added wear resistance and better shearing.

Have you done any performance cutting with the ATI 425?

 

[Mecha]

Sam,

I have seen the similar through a Strider-Horton collaboration, using Beta Ti Level 4 strike plate.
The edge was carbidized for added wear resistance and better shearing.

Have you done any performance cutting with the ATI 425?

I haven't done any performance cutting with it yet, I've just begun to mess with it and see good potential. I'm sure it would cut way more aggressively with a tungsten carbide edge treatment, but that's for future blades.

I just looked at the knives you're referring to. There is a good chance that it is the exact same alloy I just used for the knives in this thread, which is an alpha-beta alloy similar to grade 5. Other than that I better hold my tongue.

 

[Storm Crow]

Very interesting. All over my head, of course. Good work!