Nafi' (may Allah have mercy on him) said: A slave was in charge of the slaves of the khumus, and he forced one of the slave-girls among those slaves and had intercourse with her. So Sayyiduna Umar (may Allah be pleased with him) flogged him and banished him, and did nothing to the slave-girl, because she had been forced.
It is also reported from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that he imposed the hadd on a slave-girl and banished her to Fadak. Sayyiduna Ali (may Allah be pleased with him) said concerning an umm walad that she is to receive the hadd but is not to be banished. Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: She is to receive the hadd and also be banished, and the same is reported from Sayyiduna Ali (may Allah be pleased with him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحدود / 17096
Abu al-Zinad (may Allah have mercy on him) narrates from the jurists of the people of Madinah that when a slave or a slave-woman commits zina, each of them is to receive fifty lashes, and there is no banishment for them. And they used to say: Whoever incurs a hadd while a slave, and it is not carried out on him until he is freed, his hadd is that of a slave.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحدود / 17097