ΔE 12.7, fair: the same colour family, but not a straight swap. Corvus Black is a little darker than Hardened Carapace.
Can I use Corvus Black instead of Hardened Carapace?
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Corvus Black is a little darker than Hardened Carapace.
Can I use Hardened Carapace instead of Corvus Black?
The same difference applies the other way round: Hardened Carapace is a little lighter.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.