| Popis: |
Stainless steels are desirable for their good corrosion resistance and mechanical properties and are widely used in seawater exposure conditions that require high hardness. Heat treatment procedures to increase the hardness of stainless steel affect microstructural, compositional and surface properties of these materials, hence affect their corrosion resistance. To investigate this relationship a series of corrosion resistance and mechanical tests in room temperature and ambient pressure has been conducted for stainless steels (duplex 2101, duplex 2205, 17-4, 17-7, 15-5, 316, AL-6XN, Inconel600, ATI800, ATI347, 420) that are exposed to simulated seawater conditions to evaluate them in annealed and hardened conditions. Preliminary salt solution spray tests have indicated that duplex stainless steel 2205, stainless steel 17-7, and stainless steel 15-5 have better corrosion resistance than other alloys in annealed condition. A series of electrochemical impedance and cyclic potentiodynamic polarization measurements were conduced for duplex stainless steel 2205, stainless steel 17-7, and stainless steel 15-5 in order to evaluate their corrosion resistance both in annealed and hardened conditions. Mechanical tests include micro hardness tests on annealed and hardened alloys, and charpy impact tests on hardened alloys. It was shown that the final selection of materials was primarily controlled by their corrosion resistance, as the mechanical properties of the alloys show only slight variation. The mechanisms that lead to changes in corrosion resistance due to heat treatment processes are discussed. |
