Nitrogen is one of the most effective elements for improving not only strength but also corrosion resistance of stainless steels. As many researchers also have indicated the advantage of nitrogen for high temperature application as well as corrosion properties, the recently developed corrosion resistant austenitic stainless steel, DSN9, which contains 0.5mass% nitrogen and can be produced through the conventional arc furnace process, is one of the most attractive candidates for heat resistant alloys. In this report, mechanical properties of DSN9 at elevated temperature are evaluated and discussed.
DSN9 of solid solution has a higher tensile strength at elevated temperature than heat resistant steel SUS310S and also has almost the same creep rupture strength as heat resistant steel SUH660. After cold working of 60% reduction, DSN9 has a higher strength at elevated temperature than SUH660. The cold working over 60% reduction leads to a high hardness of Hv450 due to work hardening, and the aging at 723K to 823K also leads to a higher hardness of Hv540 due to strain aging of nitrogen or precipitation hardening of Cr2N. Furthermore, it maintains a hardness of Hv500 after aging up to 873K which was higher by 200K compared to conventional cold worked SUS301 for gaskets. This enables excellent seal performance even in high-temperature environments of 673K and above, which was problematic for conventional gasket materials.
