Mn in CA6NM martensitic stainless steel

Mn is a kind of element that expands the austenite phase zone in the phase diagram. In steel, the stability of Mn to austenite is only below Ni, which can improve the hardenability of steel. Thus, in super martensitic stainless steel Mn can replace Ni. But, the corrosion resistance of stainless steel with low Cr content will decrease due to the addition of Mn. When the content of Cr in stainless steel is high enough (17%), this effect is no longer obvious.