Understanding the Microstructure of Stainless Steel

Having difficulty differentiating stainless steels?

​The term “stainless steels” covers a wide range of compositions and microstructures. There are martensitic stainless steels, precipitation hardenable stainless steels, ferritic stainless steels, austenitic stainless steels, and duplex stainless steels. Within some of these categories there are often sub-categories, such as “super duplex stainless steels.” In general, all stainless steels contain a minimum of 12% Cr, although there are a few lower Cr alloys, and numerous alloys with much higher Cr contents. The topic is complex and challenging, especially for novices.


This presentation will illustrate the microstructures of different types of stainless steels, including the detrimental constituents. Examples of etchants used to identify primary and secondary phases will be presented. The influence of solution annealing temperatures on the grain growth of austenitic cold worked stainless steels will also be discussed.