Hi Jim
to the Surface Engineering Forum.
Stellite 6 and WC/CoCr HVOF coatings seem to be in favour for thermal spray coatings for hydro-power applications. Interesting though, I not seen any direct comparisons between these two specific coatings. The nature of erosion, cavitation and corrosion in these applications is very complex. While one coating may perform better than another in one specific application, this may be reversed for another application, say like when there is more sand or silt in the water, making erosion a more dominant factor. As yet I only heard of Ultimet material being used as weld overlay, but it does sound like a possible alternative to stellite 6 as an HVOF coating. The only way really to find out is to test them side by side in the same conditions as your application.
These links should be of interest on this subject:
(Sorry all these links are now dead)