Chiang Mai Journal of Science

The martensitic stainless steel AISI 440C was cyclically deformed using rotary bending fatigue tester. The fatigue lifetime as well as performance of the martensitic stainless steel AISI 440C was represented by S-N curve. The conventional mechanical surface treatment (deep rolling at room temperature) was performed on martensitic stainless steel AISI 440C to enhance the fatigue lifetime of the martensitic stainless steel AISI 440C. Compressive residual stresses at the surface and in near-surface regions of the conventionally deep rolled condition served to inhibit and retard crack initiation and propagation as a result of higher fatigue lifetime. Its fatigue lifetime at a stress amplitude of 750 MPa was 2.9 x 10⁶ cycles, whereas the fatigue lifetime of the untreated condition of only 91,000 cycles was detected. Furthermore, the conventional deep rolling was modified to the high-temperature deep rolling. It was found that the deep rolling at temperature of 300 °C possessed maximum fatigue lifetime (3 x 10⁷ cycles). A superior fatigue lifetime of the high-temperature deep rolled condition can be attributed to the strain ageing effects.   Keywords: Fatigue; Deep rolling; Residual stress; Strain ageing; Stainless steel