Stellite 6 over Alloy 625 weld overlay

[Ratheesh_n]

Members,

We have a case of valve disc material F44 and its weld overlaid with alloy 625(NICrMo3) and followed by weld overlaid with Stellite 6.

1. Is it a recommended method to follow and what must be the reason for doing the corrosion resistance overlay before hard facing.
2. What is the recommended thickness for both alloy 652 layer and stellite 6 as there will be dilution issues.

 

[SPDL310]

To answer your questions:

1.) This is typically what is called a butter pass. The alloy 625 is used as a buffer between two incompatible materials. Welding the Stellite directly to the F44 may cause cracking and non-boded material.
2.) for the correct procedure you would need to check with a welding specialist. Generally if you are working with a weld shop they will already have an approved procedure, or have a good idea as to what can be qualified. For valve bodies the overlay thickness is arround 0.125" after machining, and usually not over 0.25 inch. I would expect the Stellite to be less than the 625.
3.) How large is the disk? At smaller diameters it may be more cost effective to produce the disk out of 625 or another material that wouldn't require the butter pass, and just add the Stellite.