The hardest steel you will find in a razor is some of the vintage Swedes.
But none of them goes above 62. An dthere is a good reason for that.
beyond that you won't have the right conditions in the steel to produces the sharpest & smoothest edge.
Hardness is but one factor in steel.
Here is a very brief introduction
http://zknives.com/knives/articles/glossaries/mtlgterms.shtml
There is a reason metallurgy is a whole field of science. It is very complex.