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Piston pin

Piston pin

Piston pin

Hi all,
I'm trying to find a steel alloy piston (gudgeon, wrist) pin that is a rating of 70 HRC (760 brinell hardness).
This steel must be able to be processed through nitriding chemical process to emphasizing the hard wearing properties of the carbon in the steel to the surface.
Steel stable nitrides include chromium, molybdenum, aluminium, vanadium, tungsten and i believe nickle is one also.
Anyone got any ideas what alloys can achieve this hardness rating with out being like glass?

PS: Nice easy question for my everyone first question on here ha. Hope everyone is well.


RE: Piston pin

What is wrong with traditional nitriding grades (with Al)?
Their case hardness reaches over 1000HVN.
How deep of a case are you after?

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P.E. Metallurgy, Plymouth Tube

RE: Piston pin

Hi Ed,
As Al wouldn't be great as i'm trying not to use DLC (diamond like carbon) coatings as it is expensive when producing a fair amount.
Al wouldn't give use the strength we need without DLC.
I'm trying to maximize on strength, minimize weight and cost.
I'm currently looking at the M2 molybdenum high speed tool steel.
Which is rated at 65 HRC before nitriding. Think this will do the job.
Unless one of the other M high speed tool steels would work better. M3-M10.
what do you think?

RE: Piston pin

what size do you need ?

It used to be that the thick paper engine parts catalogs behind the counter in every parts store included "progressive size" charts for most of the parts families.

Nowadays such info is a little harder to find.


RE: Piston pin

No, nitriding alloys are steel with Al in them. They use Cr, Mo, and V to strengthen the alloy, and the AlN to give surface hardness.
Virtually all tool steels are >RC60 when quenched and give a low temperature temper.
The problem with nitriding tool steels is that most of the nirtide forming elements are tied up in carbides, this is what makes them hard.
How are you going to nitride? low temp or higher temp? Ion?

P21 is an interesting grade. It is usually supplied Q&T at about 35RC, then after machining it is aged to reach 40RC in the core, and often given a low temp carburizing or nitriding treatment at the same time to raise surface hardness.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Piston pin

If your goal is wear resistance, include deep cryogenic treatment into your thermal treatment. This will increase the wear resistance considerably.

RE: Piston pin

Thanks for your help budding engineers, some points helped me get to the answer i was requiring.
I will try to help you all where and when i can

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