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Can we use Grade 410 Stainless Steel for replacement of Grade 420 Stainless Steel? The application is for engineering components which have torsional and fatigue load.
The reason for the substitution is that 420 is not commonly available in the Indian market. Can we use 410 stainless as a replacement for 420 stainless? Does it has any major differences with regard to chemical and mechanical properties?
In general, I would be hesitant to switch the grade of stainless steel used. You are asking to switch from a more unique grade to a common grade. There was probably a good reason why the grade 420 was chosen for the original design.
With that in mind, the differences between the two grade seem to mainly be that 420 is harder than 410 (see these references: 410 and 420).
From what you have described of the requirements (e.g. fatigue is an issue), it seems strange that grade 420 was originally specified. Typically a harder material is more brittle and has a lower fatigue strength. Using that one factor, it would seem that 410 would be an OK substitution. The original designer should have known this though. There is probably a good reason why grade 420 was chosen.
If you can't ask the designer, it would not be a good idea to substitute a cheaper material.
Yes and no. The basic difference is carbon content, which is very important. You did not define heat treatment which makes a great difference with the carbon. If both are hardened and tempered at high temperature (like 1300°F), they will have almost identical properties. Traditionally, 420 with 0.15% min. C is used for cutting instruments and cutlery. It is generally not a good choice for torsion and fatigue stresses. The 410 (0.15% C max.) is a much better choice, depending on hardness/strength. 410 can have low toughness, 420 is expected to have low toughness. Also, 410 with 0.04% C is a very different material from 410 with 0.14% C. It sounds like you need a metallurgist; I would say the original choice of 420 was poor.
Note: a 13% Cr with 0.150% C could be both 410 and 420.
