Effects of check corrosion on high cycle fatigue properties of nickel-base single crystal superalloy

Abstract

In order to study the effects of check corrosion on the high cycle fatigue properties of a kind of nickel base single crystal superalloy, the samples with standard heat treatment were corroded twice and four times with FeCl3+HCl+H2O, respectively. Then the surface topographies of uncorroded, twice corroded and four-time corroded samples were observed with Leica DCM8 confocal microscope and SEM. After that, in ambient atmosphere, the uncorroded and four-time corroded samples were subjected to rotary bending high cycle fatigue (HCF) testing at 760℃and 980℃, respectively. The results show that the surface roughness of uncorroded samples is low, and there are many longitudinal fine scratches in parallel resulting from polishing on the surface. After twice corrosion, the scratches are reduced, the corrosion pits appear in interdendrite areas, and the surface roughness increases. After four-time corrosion, the scratches are removed completely, and the depth of corrosion pits and surface roughness further increase. The high cycle fatigue property of the alloy at 760℃ decreases after four-time corrosion, and the high stress amplitude zone is more affected than low stress amplitude zone. However, the high cycle fatigue property at 980℃ is rarely affected after four-time corrosion.

Keywords

• single crystal superalloy
• corrosion
• fatigue
• surface integrity