Hi Vdao

I have not been involved in the welding of these cast alloys, but the corresponding wraught alloy is Monel. The real difference between these two alloys is that the M30C contains Niobium. This will result in greater solid solution strengthening than is the case for M35-1, so M30C has a slightly higher yield strength. As a general rule, I would think there will be little difference in the weldability of these two, although the increased presence of Nb Carbides in M30C may introduce a slight decrease in weldability.

If I was doing a material selection, I would rather base my decision on the yield stength requirement / cost / availability rather than the weldability when deciding between these two alloys.

Regards
Niekie