Warning: SPOILERS for Iron Man #25
Marvel's Iron Man is a billionaire genius capable of creating new and status quo-breaking technology, but Tony Stark just revealed he can even create an artificial version of Thor's hammer Mjolnir - and make it better than Odin ever could. Stark technology is the envy of the world and is only rivaled by Black Panther's Wakanda-created vibranium tech, but Iron Man and his ego continue to push the limit. In Iron Man #25, he finally reveals a great achievement: the ability to recreate Thor's hammer that would easily eclipse his old weapon.
Iron Man has always created new devices that push the boundaries of science ever since his first appearance. Before Stark became a hardware and software genius, he was known as a master of miniaturized transistors, a 1960s predecessor to microchips. Eventually he managed to shrink down his power source from a massive electromagnet inside a chestplate into the more famous arc reactor popularized by the MCU. But in the comics, Iron Man is capable of far more: he's created an AI of himself and multiple space-capable armors (which can sustain him for days of travel if necessary).
In Iron Man #25, written by Christopher Cantwell with art by Angel Unzueta, Iron Man finds a depressed Thor in Jotunheim, the realm of the Frost Giants. This occurs during the events of Unworthy Thor, in which Thor no longer carries his hammer and even considers himself unworthy of his own name (he goes by Odinson for a time being). Iron Man offers to help: "You know I can make you another hammer, right?" He considers "borrowing" Black Panther's Wakandan technology and partnering with Reed Richards to create a hammer capable of flight and generating electricity orders of magnitude stronger than Thor's own (and half-jokes about melting down Wolverine to obtain adamantium).
Iron Man's Artificial Mjolnir Will Be Better Than Thor's Hammer
Unfortunately, even if Iron Man could make such an Asgardian weapon (and his past highly suggests that he could), Thor would never use an artificial Mjolnir. The weapon has emotional significance for him, mostly because it came from his father Odin - and because no one can lift it but Thor; the test of "worthiness" is highly debated among Marvel fans, but it is a test that Thor nevertheless passes in every iteration. Iron Man would be better off designing a weapon for himself.
In multiple cases, he has done just that; his Thorbuster set of armors were specifically designed to combat the God of Thunder using Asgardian technology. These armors usually meet an unfortunate end in battle, much like his Hulkbuster armors (Tony has never definitively worn a fight between himself and the Hulk while wearing one). Iron Man may be able to make a superior Mjolnir, but to Thor, the hammer's value lies not in destructive potential but as a gift from his father.