Maraging Steel in Golf Clubs
First, understand that "maraging" has nothing to do with mirages. It's a portmanteau (one word comprised of the parts of other words) of "martensitic" and "aging." When you combine Martensite (which is a specific crystalline structure of steel that produces a harder steel) with certain aging techniques, you get maraging steel.
Maraging steel was all the rage in golf equipment circles in the early 2000s, when golf club designers began using it for the clubfaces on drivers and, eventually, also as clubface inserts on irons and other clubs. Maraging steel is harder than stainless steel, yet more malleable.
Being stronger than stainless steel allows a maraging steel clubface to be manufactured thinner, which both produces a higher trampoline effect (good for distance) and also saves a few precious grams of weight (which can be redistributed to other areas of the clubhead).
However, maraging steel is more prone to rusting than stainless steel, which limits its use in golf clubs to, mostly, the clubface.
Maraging steel itself was soon supplanted when manufacturers turned to titanium, which has the same relationship to maraging steel as maraging steel has to stainless steel: stronger and lighter. The use of titanium in golf clubs did not cause maraging steel to completely disappear from golf (affiliate link), however, because maraging steel is cheaper to use than titanium. But the use of maraging steel did, in fact, fall off quite a bit once golf club designers began using titanium.
More definitions:
