Effect of Surface Integrity of Turned GH4169 Superalloy on Fatigue Performance

Abstract

Through turning and rotary bending fatigue test, the effect of turning feed on GH4169 superalloy surface integrity, and the effect of surface integrity on fatigue life were studied. The results show that the surface roughness Ra decreases from 1.497 μm to 0.431 μm when the turning feed decreases from 0.2 mm/r to 0.02 mm/r. The surface residual stresses are changed from tensile stress to compressive stress. The depth of plastic deformation layer decreases from 8 μm to 2 μm. The surface stress concentration factor has the most significant effect on the fatigue life of GH4169. With the increase of stress concentration factor, the fatigue life decreases significantly. When f is 0.13 mm/r, the surface stress concentration factor Kst is 1.166; the surface micro-hardness is 405.27HV0.025; the surface residual stress is 82.08MPa; and the average fatigue life is 6.98×104 cycles. The multiple cracks are initiated at the machined surface defects of GH4169 superalloy specimen.

Keywords

• GH4169 superalloy
• surface stress concentration factor
• residual stress
• micro-hardness
• fatigue life