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In order to investigate the effect of stress concentration on the fatigue strength of ceramics coated stainless steel, tension-compression fatigue tests of notched specimen were conducted at 893K and room temperature. U-shaped notch specimens made of type 304 stainless steel were coated with ZrO_2-8%Y_2O_3 by the plasma-spraying method. Stress concentration factor of substrate was selected as 2.1. The surface strain at notch root was measured by using the laser speckle strain/displacement gauge (SSDG) during fatigue test. The cracking in the ceramics layer was found to occur just after a first load cycle. However, this crack was not able to penetrate into the substrate. Therefore, the cracking in the ceramics layer was found not to be a cause of a decrease in fatigue life.
