Tony Stark is famous for his seemingly limitless number of Iron Man armors. Plenty of these have been developed with specific purposes in mind, from his Hulkbuster and Thorbuster suits to the short-lived Project Argonaut. Of all of Tony's endeavors, Project Argonaut might have been the most ambitious, as it gave him a fleet of armors that he could control through his Extremis powers.
Shortly after being imbued with a modified version of the Extremis virus, Tony Stark began developing a series of armors, each tailored to a specific purpose. One of these was the Battle Argonaut suit, which was partially constructed from the most indestructible metal in the Marvel Universe, adamantium.
When these suits first appeared in 2006's Iron Man #7 by Daniel Knauf, Charles Knauf and Patrick Zircher, Tony was still reeling from having killed the Extremis- empowered terrorist Mallen, and the Extremis coursing through his own veins wasn't making things any better. Iron Man had become willing to even temporarily stop the heart of the Crimson Dynamo during a fight, leading to a minor confrontation with Captain America over Tony's trigger happy new attitude. Things took a turn for the worse when someone else turned the Argonaut suits into their personal army without Iron Man knowing.
When he is seen fleeing the scene of the murder of a man involved in the death of Ho Yinsen, Tony quickly becomes the prime suspect in that and a few other killings. Strikingly, not even Tony remembers the time he was apparently committing these gruesome crimes, but the evidence is enough to get Nick Fury to call for Stark's arrest. Thankfully, Tony turns himself in before anyone gets hurt. but though that doesn't stop him from becoming an unwitting assassin once more. The Sentry was on his tail, and he had no understanding of what has been going on, at least not until he catches up to Ho Yinsen's son. As it turns out, the son of Tony's old mentor was the mastermind behind hacking the Argonaut armors and using them to carry out his horrific crimes, even doing so with Tony still inside, completely unaware.
With the true culprit apprehended, a S.H.I.E.L.D. sniper taking out the young man triggers dozens of Iron Man suits to come to life and start wreaking havoc. This included the Argonauts, and Tony's adamantium suit proved more than capable of cutting through whatever got in its way. After going rogue, the Battle Argonaut made its way towards Russia to cause as much chaos as possible by attacking nuclear reactors in Moscow. Thankfully, the real Iron Man was able to destroy it before that came to pass by smashing it with the anti-metal frame of one of its sister Argonaut suits.
Tony's adamantium armor hasn't been seen since then apart from a silhouetted shot in 2016's Invincible Iron Man #11 by Brian Michael Bendis and Mike Deodato Jr. -- and likely for good reason. Despite its regular use in Wolverine's corner of the Marvel Universe, adamantium isn't exactly in great supply in the Marvel Universe, and even Tony Stark's vast wealth cannot make up for that fact. Beyond that, Tony's tech and weaponry have only gotten better over the years, and admantium's durability is not the only thing that Iron Man needs in the field. Then again, he could have probably used it during his most recent run-ins with Korvac. It's unlikely that the Adamantium armor will be making a comeback anytime soon, though that might actually be for the best.