The role of alloying elements in CA6NM martensitic stainless steel
Mo——the addition of alloying element Mo in martensitic stainless steels is beneficial to the strength. And also to toughness and corrosion resistance. Mo is a ferrite forming element. It can reduce the Ms temperature. The addition of Mo in super martensitic steel can significantly reduce the martensite unidirectional zone. Meanwhile Mo can promote the passivation of Cr in some reducing corrosive media. Therefore, Mo can improve the corrosion resistance of Cr-Ni stainless steel in reducing acid. And effectively inhibit the pitting corrosion of Cl– and improve intergranular corrosion resistance of steel.
However, Mo is a kind of austenite stabilization element, like Ni. Excessive addition can lead to the formation of retained austenite. In martensitic stainless steels Mo content is generally controlled below 5%.