Investigation of cracking kinetics during cavitation erosion by in-situ X-ray tomography

This proposed study investigates the in-volume damage mechanisms of X3CrNiMo13-4 and X4CrNiMo16-5-1 martensitic stainless steels exposed to acoustic cavitation using in-situ synchrotron X-ray tomography. A dedicated setup called Motorized Ultrasonic Cavitation Erosion Facility (MUCEF) was specially designed to perform X-ray 3D characterization during interrupted cavitation erosion tests. 3D images were recorded at high resolution (voxel size = 0 . 32 μ m ) and at high energy (70 keV) on the ID19 beamline at the European Synchrotron Radiation Facility (ESRF). Specimens were scanned after every 10 min of exposition to acoustic cavitation up to 130 min. The analysis of the 3D images sequence shows that mode fatigue cracks systematically propagate from the surface to the volume with an angle between 20 and 30°. The cracks then deviate to become parallel to the surface at a depth between 9 μ m and 13 μ m . At an exposition time close to the incubation time, particles are then emitted with a typical size of several thousands cubic micrometers. The emission of particles is associated with a bending of ligaments (mode I propagation mode). With exposition time, more cracks are later nucleated in the craters left by the emitted particles with a similar propagation scenario. • Damage mechanism of martensitic stainless steel under cavitation studied. • In-situ synchrotron X-ray tomography reveals cavitation damage mechanisms. • Cavitation-induced mode II fatigue cracks initiate systematically at surface. • Cracks systematically deviate in the volume at a depth between 9–13 μ m. • Extended cavitation exposure promotes cracking at crater bottom zones.