WPS

In Mechanical Engineering one of the essential courses you take is "Metallurgy" & Chemical Attributes of Materials. Any of these sound familiar ? I suggest you research and look into this yourself without pushing the liability onto others.

First, material selection is not the job of a qaqc, assuming that is a quality person.

Filler metal is selected for this material the same as most others. By consulting the applicable welding specifcation and process sheet for that project.

Since we don't know where you are it is hard to say what the controlling documents would be.

Where I live we use AWS specs, mostly, for non spacecraft materials. Download AWS welding