stellite coating on 17-4 PH

[CPless]

I'm working on a conveyor track that needs to be very strong (190ksi), wear resistent and corrosion resistant(located on a ships deck)...
The two options I am thinking of are using 440C or using 17-4PH with a stellite coating. I'm concerned that the coating may crack and also create a galvanic corrosion problem. The conveyor chain is 4140 but will be fitted with brass shoes on the mating surfaces.

Is this coating system likely to work or would I be better off going to a different set-up?
The track will most likely have to be welded as well...

 

[metengr]

Please elaborate on your last statement regarding welding.

At a strength level of 190 Ksi (I am assuming yield strength here) any welding after heat treatment will adversely effect mechanical properties, regardless of material. You need to consider mechanical attachment of the track in the field, versus welding, if you intend to maintain this strength requirement. Also, at this strength level any martensitic stainless or PH stainless steel will not be as corrosion resistant, and will be susceptible to chloride stress corrosion cracking (CSCC) or hydrogen embrittlement on open sea.

Some materials that could be considered for the track are quenched and tempered low alloy steel (AISI Type 4340) with a surface heat treatment like nitriding to provide for increased wear or a quenched and tempered alloy 300M (this is a modified version of 4340).

To avoid exposure to surface corrosion pitting from moisture/chlorides and possible hydrogen embrittlement, I would paint or use a barrier coating on any exposed track surfaces, and keep the wear surface on the track greased.

 

[EdStainless]

You will not be able to weld fabircate any of the high strength alloy grades. The require very specific heat treatments to develop their strength, welding will result in hard/soft spots. The system will need to be mechanically assembled.
Have you considered a carbide spray for wear coating? Coatings applied by HVOF or a similar process provide excellent wear resistnace and don't damage the underlying material.
Yes, you will need to seal/coat the entire structure in order to suppress corrosion.
Marine hardware is complicated field.

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Corrosion never sleeps, but it can be managed.

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