Pistons

[Liberty Lips]

Having read the referenced article "Nickel vs. Monel: The Battle Rages On" by Brett Getzen, I’m left a bit confused with more questions than answers. I’ve read that monel is more corrosion resistant than pure nickel and even stainless steel, and is also stronger than nickel, which is why monel is often preferred for seawater conditions. I think the alloy that was referred to in my reading is Monel 400, and I don’t know if that is the preferred alloy for brass instrument pistons, which may be why I’m confused, but Brett even mentions that monel is harder than nickel in its original state. But if monel is more corrosion resistant than pure nickel, I don’t understand why there would be such a high incidence of corrosion in monel pistons in the tests that are referenced, as compared to nickel plated pistons.

Furthermore, earlier in this thread Brett Getzen said "Now if we are talking all things being equal (build quality, tolerances, honing, lapping, etc...) my money is still on nickel plated, nickel silver pistons," however the article states that Getzen pistons are "nickel with nickel plating". I suspect that their pistons are nickel silver, an alloy of usually 60% copper with nickel and zinc, rather than pure nickel, otherwise why would nickel pistons be redundantly plated with nickel? But then it is stated that "starting with nickel tubing provides a stronger bond between the layers," and also "if the nickel plating does wear, you’re left with an exposed section of nickel tubing...while it’s not as hard as the plating, the nickel tubing is harder than an exposed piece of monel would be." Did he mean to say that nickel silver tubing provides a stronger bond? That confuses me as well, since nickel silver has a smaller percentage of nickel than monel, and also nickel silver tubing would not be harder than monel. Wouldn't nickel silver soften more than monel would when the ports are braised in, due to that smaller percentage of nickel? And if that is true, wouldn’t monel then be a better material for the pistons than nickel silver over which nickel plating would be applied due to its corrosion resistance and relative strength? Perhaps the reason is because nickel silver is a less expensive alloy than monel, and all things being equal the less expensive alloy makes sense.

Anyway, or anyways depending on your colloquial preferences, I wonder if anyone (Brett?) could clear this up for me. It might help the OP as well.

[Goby]

[Liberty Lips]

Well, there are two issues, and I think only Brett Getzen can answer them. Are Getzen pistons made from solid nickel tube stock, as his essay on the Getzen website implies, or are they made from nickel silver tube stock, as he has suggested here?

If they are made from solid nickel tube stock, why then would they be redundantly plated with nickel?

If they are made from nickel silver tube stock, then I have two questions. First, is nickel silver less susceptible to softening from annealing than monel is, and secondly, does nickel silver provide a stronger bond with the nickel plating than monel does? Brett makes these two points in his essay, but those points were made about solid nickel rather than nickel silver. According to what I’ve read, both points are not true about nickel silver, since nickel silver is a copper alloy and monel is a nickel alloy. If Brett disagrees it would be interesting to know his reasoning.

It would seem to me that the best and least expensive way to manufacture a piston would be to use solid nickel tube stock, and after completing the installation of the ports simply lap the pistons in without plating them first. That would provide the superior nickel finish, and there would be no matter of the plating wearing off after years of use.

[Divitt Trumpets]

There are many "flavours" of nickel plating. Some of it is extra hard, some of it is impregnated with Teflon or other things. Playing gives you different options that tube or rod stock doesn't offer.
I doubt they use pure nickel for the piston tubes because of the difficulty in turning and honing it vs an alloy of copper and nickel that is meant for specific types of working.
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[Andy Cooper]

[Doug Elliott]

The same metal can be different hardnesses depending on how it was manufactured and whether it was heat treated, annealed, tempered, etc... based on the temperatures it was subjected to and how long. And if it's tubing, the way the tube was drawn, which hardens it.
For example the brass I buy is listed as "half hard" but it varies quite a bit from one rod to the next, which I can clearly tell when I'm cutting it.

[Divitt Trumpets]