I was wondering if anyone could help with the following query;
We have a client who wishes to have 2.5% Mo (increased pitting resistance) and therefore 316L is not an option.
It has been suggested to chose duplex. However, I understand this material is highly expensive and only chosen if there is a high risk of chloride attack, stress corrosion cracking, or if high strenght is required at high temeprature. Since none of these apply to the intended application can anyone suggest an more economic alternative. In principle the only additional requirement above 'normal' 316L s/s is the 2.5% moly requirement. I assume that 316L welding wire cannot be used since SFA/AWS5.9 states it can be as low as 2% Mo.
Damian.
Duplex is a bit overkill. You could go with 317, or a nickel alloy with Mo(for example NiCrMo-3,4, or 10). Ni will be pricey too but it won't engender the welding issues that duplex does. The advantage of the Ni is you won't have to worry about Mo segregation.
js55,
Thanks very much for the tip! Damian Kotecki has warned about excessive sigma phase compounds impairing corrosion resistance and reducing notch toughness, so best avoided. It's also wickedly expensive.
Damian.
You can specify (but may not get) any level of moly that you want -
I believe there was a grade called 319 which was 2.5 % Mo minimum but that was in the olden days of the ~ 1966.
If it is just the moly factor which is critical you should be able to ask for 2.5 Mo minimum or maybe just go
with Type 317 L -
if you look at the composition of AISI 316, UNS 31600, the range of Mo is 2 -3 % so you can ask for a SS 316 with a minimum of 2.5%, i've seen this requirement sometimes or as someone else said you can use the SS 317 wich has a min of 3% of Mo.
V
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