I have moved out of a rental house that I lived in for 2.5 years in Oregon. The wood stove was our only source of heat. Over the course of my stay, bringing in firewood & setting it down, I broke 3 tiles on the hearth pad. I have bought three exact replacement tiles & set up a time for a licensed & bonded contractor to replace the tiles ($75 at my expense) but the landlord said he won't allow that. He wants a brand new hearth, I estimate that to cost more than $400. The contractor also informed me that the hearth was a "homemade" job to begin with & not professionally tiled.

Can he use my security deposit to buy a brand new hearth pad?

He can try, and you will have to sue for return of your deposit.

** most likely he will just replace the tile his self.

But in court, you can ask for proof that he paid that much, also call your repair person in to testify that it did not need to be replaced.

Document with photos

And to be honest, normal wear and tear on flooring may not even be your expense anyway.

I see no reason why he gets to keep your deposit for this (I have been both tenant and landlord in my 67 years).
I would tell him that he has to return your deposit by the 30th day after the end of the term or he can be taken to court for double or triple, depending on your state. Google your state and return of security deposits. Not all have double or triple.

And as stated, he has to provide receipts for any repairs he does in order for work to be taken out of your deposit. Tell him that it is in his interest to have the work done your way, or you will sue.