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.
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?"
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.
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.