Maraging steel, which is a super-strong steel, is the hardest-known metal in the world. It is an iron alloy that contains high amounts of cobalt, nickel and molybdenum.
Maraging steel is very hard and tough because of the heat-treatment process it had to go through. It has the ability to withstand tension or pulling forces. Also, a lot of energy is necessary before this type of steel is deformed. Another property of maraging steel is fracture toughness, which means that even when it fractures, it doesn't break easily. This metal is used for aerospace applications and high-performance engines because it can retain its characteristics even at high temperatures, even higher than most steel.