440A is a high carbon martensitic stainless steel that is AOD melted. This alloy can be heat treated to extremely high hardnesses. It has slightly less carbon than 440B and 440C giving it better machinability but less hardness. The combination of good wear resistance and high hardness makes this alloy an excellent candidate for cutting tools and knife blades. It also is often used for dental and surgical equipment.
Grade 440B stainless steel is a high carbon martensitic stainless steel containing good strength, moderate corrosion resistance and ability to obtain and maintain wear resistance and excellent resistance.
440C is a high carbon martensitic stainless steel that has slightly more carbon than 440A and 440B giving it the highest hardness of any martensitic stainless alloy. This grade has excellent wear resistance making it perfect as a bearing steel used as ball bearings and bearing races.
440FSE is a high carbon martensitic stainless steel that is AOD melted. This alloy is considered a free machining grade because of the added Selenium creating a better machinability version of similar grades 440A stainless and 440C stainless. This grade is suitable for non-galling and non-seizing applications. This alloy is often considered for general machined parts requiring higher hardness values than other free machining grades such as 420F.