Official Answer
Answer
HIDF occurs when monatomic hydrogen diffuses into the high-stress regions of a steel lattice, typically at the grain boundaries. For a wave spring under preload, this hydrogen lowers the critical stress intensity factor $K_{Ic}$, leading to the sudden, brittle fracture of the spring hours or days after installation. This is common in oil-tempered SAE 1070 springs that were electroplated without sufficient baking. The failure is characterized by an intergranular fracture surface. Diagnosis is confirmed through SEM (Scanning Electron Microscopy) analysis showing 'rock-candy' morphology on the fracture face.
