Stellite on high temperature valve spindles and dilution

[kclim]

Have a query regarding on above subject, mainly as it applies to the power gen industry (turbine valves).

My understanding is that it is common practice to apply stellite 6 on alloy steel spindles to prevent oxide build-up and associated jamming.

How critical is dilution given the application?

Reading some literature from Deloro, dilution of iron in the stellite reduces hardness and wear resistance, although I would've thought wear resistance isn't a big priority here.

Dilution with iron also has the unusual side-effect of increasing toughness as the brittle carbide phase content is effectively decreased.

The key property I would've thought would be the oxidation resistance - I imagine this is mainly related to the Cr content, so I'm not sure whether iron dilution (say up to 20%) would affect this much.

Is anyone able to comment?

 

[metengr]

kclim;
We have Stellite 6 on most if not all of our turbine stop and gov valve seats. No issues with dilution provided you have enough of a weld deposit. We usually have 1/8" with absolutely no issues. If youlap the Stellite over the years this can still leave an effective weld deposit. The problem is machining versus lapping.