Molybdenum

It is commonly present in high speed tool steel, carburizing steel and heat resisting steel. This forms carbide having high wear resistance and retaining strength at high temperatures. Mo generally raises harden ability and helps enhance the effects of other alloying elements as like Mn, Nickel and Cr.

Tungsten

It is important ingredient of tool steel and heat resisting steel and normally has similar effects as Mo however 2 to 3% W has similar effect as 1% of Mo.