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Sulfamate nickel plate over 304L stainless steel in a high speed rotating member

The part in question is a 3300 rpm rotating member of an oil-field centrifuge. It has been machined out of concentricity. A suggestion is to use sulfamate nickel plating (to build up OD)and re-machine. The 3 surfaces include a bearing & 2 seals. Is this an acceptable method, (will there be a durable bond)? The bearing fits tight over the surface, will there be a problem with the seals?

Ted Mitra
- Conroe, Texas
2006

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First of two simultaneous responses --

Yes, sulfamate nickel is similar in metallurgical properties to stainless, and an experienced shop can apply it with good adhesion. Hard chrome might be better. Although it will have to be ground to size rather than machined, it is more reliable and will wear longer.

Jeffrey Holmes, CEF
Spartanburg, South Carolina
2006

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Second of two simultaneous responses --

A lot of that is going to depend on what the parent metal is and what the load that is applied is. Jet engines rotate a lot faster and have a huge safety requirement, so they normally use chrome. Engineering, not decorative. if your load is light, sulfamate might work. Adhesion depends on the plater and the parent metal. Some is a lot easier to plate than others.

James Watts
- Navarre, Florida
2006

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You may have forgotten to mention it but, are you considering a pre machining to restore concentricity before the build-up? It would be advisable if it doesn't add too much time and cost for it will assure you to have a uniform layer of whatever buildup metal you choose. And here I'd personnaly go for the sulfamate nickel if the required build-up is above 0.010" or more per side. Chrome, though harder, has a very limited elasticity (less than 1% against 15% for Ni). You didn't give details of the conditions but if that part is subject to very heavy loads and deformation during operation the thicker the build-up the more stressed it'll get. If your main concern is the wear at seal areas, nickel will behave very much like the SS specified as base metal by the OEM. Chrome will outlast both several times in that respect.

Guillermo Marrufo
Monterrey, NL, Mexico
2006