Is it established that the wives of the Prophet (peace be upon him) and the female Companions did not visit each other, and is it permissible for a husband to prevent his wife from visiting her friends on the condition that he accompanies her?

There is no harm for a woman to visit her righteous friends with her husband's permission. If he does not give permission, then it is not permissible to disobey him. As for the husband stipulating to go with her, he should not do so unless he fears harm upon her or embarrassment for her friend's family.