Material and fatigue investigation of a white etching crack on a marine bevel gearWednesday (27.05.2020) 15:10 - 15:30
The microstructure of a white etching area around a subsurface crack on a marine bevel gear was studied by means of light microscopy, scanning electron microscopy, transmission electron microscopy and atom probe tomography. The material shows clear signs of recrystallization in a 20 μm band around the crack with grain sizes in the area of 10-20 nm. Using electron diffraction and atom probe tomography, the phase of the nanocrystalline material was determined to be ferrite with visible Nickel segregations on the grain boundaries.
To support the material investigation, hardness and hydrogen measurements and multiaxial fatigue analysis of the gear tooth were carried to understand the risk of subsurface cracking.