In steelmaking this high melting point metal is used as an alloying element in engineering and stainless steels. It improves corrosion resistance and hardenability, enables steel to perform at elevated temperatures – and confers higher strength at these temperatures – and improves weldability.
In stainless steels the highest content is about 6%, but the most widely used moly-containing grade of stainless (austenitic 316 / 1.4401) has 2.5-3% Mo.
In other alloy steels the moly content is usually below 1%, but there can be as much as 9-10% in high speed steels.
Molybdenum containing steels are used to meet demanding in-service duties in a wide range of applications – from mining and power generation, to the automotive, aerospace, process and oil/gas sectors. And for more detail click and see wikipedia entry.