What is the difference between aus - 8 and 440 stainless steel blades?

440 is a family of steels, , including 440A, 440B, and 440C. AUS-8 is very similar to 440C. WITH PROPER HEAT TREAT both 440C and AUS-8 make a very good stain resistant steel choice for shorter knife blades. Either will hold a good edge in the rockwell C 57-60 range but remain sufficently tough to prevent snapping or edge chipping. Remember, however, than no steel in the world can't be ruined by a poor quality heat treatment, either by being too soft and wearing quickly, or too much above the working hardness, and chipping, so knowing a knife is made of either 440C or AUS-8 doesn't garantee quality; they are relatively old alloys which are relatively cheap to produce, so many junk knives use them. 440A and 440B arn't quite as good - a knife that claims to be made with just "440" is most likely A or B, and most likely inferior.