Yes. If someone is legally a slave then it is permitted to buy, sell, gift, inherit, lend, pledge and lease that slave. Every transaction that is permitted for an object is also permitted for a slave. That is exactly what slavery is by definition.
إذا زنت الأمة ... ثم إن زنت الثالثة فليبعها، ولو بحبل من شعر
If a slave-girl commits illegal sexual intercourse ... and if she commits it a third time, then he should sell her even for a hair rope.
— Bukhari
أخذه النبي صلى الله عليه وسلم فقال من يشتريه مني
The Prophet (ﷺ) took the slave and said, "Who will buy this slave from me?"
— Bukhari
ومن ابتاع عبدا وله مال فماله للذي باعه إلا أن يشترط المبتاع
If somebody buys a slave having some property, the property will belong to the seller unless the buyer stipulate that it should belong to him.
— Bukhari
There are some minor limitations on this, for example it is not permitted to sell a slave in a way which would cause separation between mother and child, or to sell a Muslim slave to a Kafir owner, or to sell an Umm Walad etc. However I am assuming that you are asking about the general ruling.