Effects of the chromium-molybdenum-nickel

Question

Write down the metallurgical explanation of effects of the chromium, molybdenum, nickel, and carbon in the stainless steels.

Answer 1

Alloying elements in the stainless steels can be alienated in two major categories namely austenite as well as ferrite stabilizers. Austenite stabilizers should be present in austenitic and martensitic STSs (or austenite at annealing temperature is precursor phase for such two categories though for the latter group, it converts to martensite ere cooling down to room temperature). In order to alleviate austenite at annealing temperature, the ratio of austenite to ferrite stabilizers should be high. The strongest austenite stabilizers are N, Ni, C, Mn, and Cu whereas elements such as Cr, Nb, Si, Ti, and Mo are the most significant ferrite stabilizers. Ni-equivalent to Cr-equivalent ratio is an effective manner to quantify the austenite formation tendency of STSs. There are dissimilar expressions for Creq as well as Nieq, one of which looks like this: Creq=Cr+1.37Mo+1.5Si+2Nb+3Ti) and Nieq=Ni+0.3Mn+22C+14.2N+Cu.