Fastner Material Nut for ASTM A193 Gr B16 Stud

Dear All,

My name is Priyen. I am working in control valve industry and designing desuperheater and multi stage control valves. Today I have come across a small issue about the fasteners. Generally we used to give Fasteners combination of ASTM A193 Gr B16 with ASTM A194 Gr 4. But somehow the Gr4 nut is not available in market and we are finding alternative for that. I came across ASTM A194 Gr 7 which has same properties with some amount of chromium in it. Can you guys please share your views about this combinations.

Thanks..