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[MW:12203] RE: 12201] Hairline cracks in stellite 6 coating (HF) - A216 WCB

By Materials & Welding
Dear Sir,

It's true that this alloy sometimes has small crack in its surface, it is
mostly used for wear resistance and in such cases this won't be a problem.
The alloy Stellite 6 has less tendency to crack than for example Stellite
12, but only when multi-layer technique is used. In single layer
applications you probably will have small cracks.
So it is possible to apply the material without cracks but in cases where
the hard facing also is used for corrosion resistance or for a perfect
sealing you perhaps better can choose another wear resistance alloy in order
to avoid cracks.

Met vriendelijke groeten / Best Regards

Herman Pieper

Pieper Quality Support & Inspection
Phone: +31 (0)521 380083
Fax: +31 (0)84 7539225
Cell: +31 (0)6 51691215
www.pieper-qsi.nl

-----Oorspronkelijk bericht-----
Van: materials-welding@googlegroups.com
[mailto:materials-welding@googlegroups.com]
Verzonden: vrijdag 12 augustus 2011 10:01
Aan: Materials & Welding
Onderwerp: [MW:12201] Hairline cracks in stellite 6 coating (HF) - A216 WCB

Is it true that stellite 6 HF will leave hairline cracks on the surfece?,
one of the reputed valve vendor is quoitng that

"Seat overlay made of Stellite 6 is possible but not recommended by us. We
clearly mention that it is not possible to perform a Stellite 6 completely
free of hair cracks. Probably after final machining the surface will show
hair cracks which is normal in case of using Stellite 6 and this do not
affect the sealing function. We normally do not use Stellite 6 because of
this fine cracks and because of much better experience with Stellite 21. If
you insist on Stellite 6 seating surface showing hair cracks will not be a
reason not to accept the valves if seat tightness test is ok"


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