X7 Alloy vs. 15.5 ph

[4Speed]

I see the mercury cleaver is X7 Alloy and the Mazco cleaver is 15.5 ph. Anyone know the difference between the 2 materials in terms of what is the better surfacing material and would be less likely to throw a blade.

[phillnjack]

x7 is also more commonly known as 17.7ph . its easier to find the comparisons this way. (not to be confused with 17.4ph)

I have no idea what would be the best for a surface prop, but maybe knowing the two metals common names will help you.

[BarryStrawn]

x7 is also more commonly known as 17.7ph

What is the source of this information?

[phillnjack]

I knew there would be non-believers that this material is NOT new . Its just new in the propeller market.

ICARUS and anyone who deals in stainless steel has info on all their alloys..

its been around a long time, different company's use different brand names for the same materials. can also call it 631 or S17700 etc

Icarus-be.com

then look up material table. its in the left side , top table 2nd from bottom, above the 15.5ph .

I will see how to upload a pdf here later, or take a decent pic and post it.

[BarryStrawn]

I know what 17-7ph is. But what makes you so certain Mercury X7 is 17-7? I think they gave up on the "Patent Pending" marketing campaign and now just call it "proprietary" but I am just curious how you determined they were using commercial 17-7ph.

Will also suggest Carpenter (www.cartech.com) as a better source for real information about stainless alloys.

[phillnjack]

Mercury called it X7 Alloy in tons of marketing, its only very recent they dropped the X7 Alloy and now just say X7.

that was what made me think and believe its 17.7ph, do I think it could of be another of the X7 alloys ? I dont think so.

we only take the makers word for it that we get what they claim it to be anyway. how many of us use special testing procedure to know what our props
are made of ?
you would need to be a bloody good metallurgist to know the difference between 17.7ph and 15.5 ph without a reliable test kit.

I wouldn't even know how to use the test kit !!!

[BarryStrawn]

I have no idea what an "X7" alloy might be other than a marketing term Mercury created for their advertising. Their claims about it being stronger and more durable read like ambiguous bull**** to me.

[staylor]

Sort of like Merc's use of the term "Full Jeweled Power" to describe the use of ball and needle bearings instead of sleeve bearings in their powerheads back in the 1950s!.....looking for real jewels, none found.....! To the topic, 17-7 stainless is probably not what Merc is using for their X7 alloy. It's a stainless that is very soft when cooled down after casting and requires secondary heat treating operations afterwards. In comparison, 15-5 and 17-4 stainless is quite strong after casting, and for most prop uses doesn't need any heat treating afterwards. It is possible to heat treat all 3 of these materials to much higher strength levels, but given current prop blade shapes and thicknesses there isn't much to be gained from doing this. If one utilized the additional strength to allow the blades to be thinner- then they will also be more flexible- since the elastic modulus doesn't change with heat treating. In some odd cases, extreme performance competition props are heat treated so they can hold very sharp leading edges for a longer time, or because they are small diameter props that are very heavily loaded. Often, 17-7 stainless steels are used for making aerospace leaf and coil springs because of the soft and easily worked condition in the annealed state, combined with corrosion resistance. The material is also suitable for making large heat exchangers and boilers- again because of the ease in working the material in the annealed state. Merc's shift from Patent-Pending to Proprietary is most likely because they couldn't get a patent for whatever they claimed was "New" about the material. Pending Patents are not published by the Patent Office, so only Merc knows what's in X7 until someone runs a piece of X7 thru a mass spectrometer....

[phillnjack]

nicely written, pretty much what I expected from mercury, over the years they have used some very exotic and professional sounding names
for some very simple things.

The pat pending is a funny thing, mercury have tried to patent loads of stuff that was already around, and so to has most large company's around the world.
Now if they had made the propeller from XL5 would they have called the prop a "Fireball" ha ha .

[spbutler]

anyone know if the X7 is a lighter prop in terms of weight vs standard stainless?

[staylor]

anyone know if the X7 is a lighter prop in terms of weight vs standard stainless?

It's only going to be lighter if the blades or hub are thinner on otherwise identical props- since all stainless steels weigh nearly the same per cubic inch of material. I believe Merc mentions in their hype that X7 blades are thinner- but they don't say thinner than what.
Doug