I don't know about rods (if you mean SMAW electrodes-most of the rods out there that I know of as 'hardfacing' are simply high tensile/yield low alloy rods) but most of the hardfacing self shielded flux cores out there are either Fe carbide or chromium carbide alloys.
The 'saturation' level would depend upon the hardness of the material in question.
With hardfacing though, it isn't so much saturation as it is size and morphology of the carbides involved.
Also 'cross checking' (cracking) is used as measure of weld procedure viability as well.
If you are goin to qualify hardfacing procedure you need to be cognizant of dilution, cross checking per inch, hardness, bonding, photomicrography of the ccarbide mistrstructure, and though the ASTM spec number eludes my memory, there is a specific abrasion test to be performed.
There is also an 'open arc' process available wherein a standard carbon steel wire is welded in an open arc with additions of carbide powder.