Failure analysis on the stub thrust washer of an electric axle

The chemical composition, fracture microstructure, hardness, fracture morphology, fracture mode and surface carburizing layer of brittle thrust gaskets from different manufacturers are compared and analyzed. The results show that cryptocrystalline martensite and granular ferrite duplex structure appeared at low quenching temperature reduced the toughness of washer core zone, causing crack growth and propagation under impact. To avoid the brittle fracture of thrust washer, impact toughness of core zone is increased by raising the quenching temperature to near +840℃, and the surface brittleness is reduced by decreasing case hardening depth.