There is a scientist named Crockett in one of the rooms in the Hubologists' San Francisco base that can harden power armor. He can upgrade it for a fee of $10,000 or can be threatened into doing it with a high Speech skill. Alternatively, one can negotiate to have fuel transferred from the Steel Palace to the USS Quetzel in exchange for his services. The process takes 1 day. However, he can only harden two sets of power armor.
If having killed the AHS-9, it is not possible to get the needed dialogue for the hardening process but it's still possible to receive the armor already given to him.