Influence of orientation and temperature on the fatigue crack growth of directionally solidification superalloys DZ125

The influence of orientation and temperature on the fatigue crack growth of a directionally solidification superalloys named DZ125 were investigated in this study. The specimens were designed based on ASTM E647 standard and the compliance method was employed to monitor the crack growth. Tests were conducted at room temperature, 760 degrees C and 850 degrees Crespectively. The longitudinal and transverse orientation were both studied in this tests. Results show that the orientation dependence is weak at elevated temperature compared with that at room temperature. However, the temperature influences the fatigue crack growth rate significantly and the largest difference can be an order of magnitude on the da/dN-Delta K graph. But the reduction in higher Delta K area of elevated temperature can still be observed. Potential reasons and hypothesis were explained in this paper. In addition, the crack growth mode appears to transfer from type I with the increase of temperature which also reflects the influence of temperature.