Corrosion fatigue of precipitation-hardening martensitic stainless steel

Corrosion fatigue properties of a precipitation-hardening martensitic stainless steel, Custom 450 (UNS S45000), were investigated. Systematic fatigue tests, including both high-cycle fatigue (HCF, S-N curves) and fatigue crack growth (FCG, da/dN-DeltaK curves), were conducted in air and several aerated sodium chloride (NaCl) solutions with variations in pH, temperature, and NaCl concentration. Results indicated that all the given aqueous media produced essentially detrimental effects on the fatigue response by reducing the HCF life and increasing the fatigue crack growth rate (FCGR) from the air values. However the variation of bulk environment characteristics had a greater effect on the HCF response than on the FCG response. An additional reduction in HCF life and enhancement in FCGR was found as a result of a decrease in pH value, an increase in solution temperature, or an increase in NaCl concentration of the salt water. Among the given variables of the bulk environment, pH effect had the greatest influence on HCF response while temperature effect had the most influence on FCGR.